Tesi sul tema "N-Heterocyclic carbenes (NHC) complexes"

N-heterocyclic carbenes (NHCs) can be used as ligands for organometallics complexes, which can then facilitate numerous catalytic applications, such as, C-H activation, small molecule activation and numerous materials applications. The use of anionically-tethered NHCs for usage with electropositive metals has been pioneered by the Arnold group within the last decade. This thesis describes the synthesis of both aryloxide- and amide-tethered NHC organometallic complexes of s-, p-, d- and f-block metals to provide a platform for small molecule activation. Once synthesised, the reactivity of some of these complexes were tested by reaction with CO2 with the aim of turning a molecule considered a harmful (environmentally), waste product into value added products, potentially providing an alternative fuel source. Chapter One introduces the use of anionically-tethered NHCs for use in a number of organometallic complexes as well as their current potential as catalysts for a number of important small molecules. This chapter focuses upon the differences between complexes tethered with anionic O, N, P, S elements, f-element NHC complexes and the use of d-block NHC complexes for catalysis. Chapter Two contains the synthesis and characterisation of a number of aryloxy-tethered NHC p-, d- and f-block organometallic complexes using the ligand H2(LArO R)2. The synthesis of SnII complexes including the synthesis of new ‘normal’ ‘abnormal’ complexes given enough steric bulk around the Sn centre due to the lone pair present in Sn complexes, preventing one of the ligands binding through the classical carbene position and therefore binding through the backbone C4 carbon. The synthesis of MII (Zn, Co and Fe) complexes to compare the solid-state structure and binding mode of the carbenes. The synthesis and characterisation of MIII (Ce and Eu) complexes to assess the solid-state structure and binding modes within f-bock complexes. Chapter Three investigates the reactivity of the MII complexes (Sn, Zn, and Fe) with CO2. Successful reactions were characterised using NMR and further treated with alkynes to target catalytic reactions. Chapter Four contains reactions to target a number of amide-tethered bis (NHC) s-, p-, d- and f-block organometallic complexes using the proligand, H4(LN Mes)Cl3. Deprotonation studies undertaken with a number of bases to give the MI (Li and K) salts and MII (Mg) salts and proved to be unsuccessful upon isolation. Reactions to synthesise the p-, d- and f-block complexes were then undertaken using in situ free carbene production as well as the attempted isolation of the free carbene, both of which also proved unsuccessful. Chapter Five provides an overall conclusion to the work presented in Chapters Two, Three and Four within this thesis. Chapter Six gives the experimental and characterising data for the complexes and reactions.

Dans le cadre de ma thèse, de nouveaux complexes de métaux de transitions (rhénium, iridium, cuivre, or) chiraux possédant des ligands NHC-hélicéniques ont été synthétisés et les propriétés chiroptiques et photophysiques ont été étudiées. Le premier sujet d’étude s’est focalisé sur l’étude de complexes de rhénium(I) cyclométallés par des ligands hélicéniques-NHC de type (N^C:) émettant de la phosphorescence circulairement polarisée. Une influence du design du ligand, des ligands ancillaires et de la géométrie des complexes sur les propriétés chiroptiques et photophysiques a été observée. Le deuxième projet a été consacré à l’étude de nouveaux complexes chiraux d’iridium cyclométallés possédant un ou plusieurs ligands N-[6]helicenyl-benzimidazolylidène. L’attention s’est ensuite portée sur des complexes possédant des ligands monodentes. Ainsi, dans le cadre d’un troisième projet, un complexe de cuivre portant un ligand NHC-hélicénique démontrant des propriétés de fluorescence circulairement polarisée a pu être obtenu avec succès. Enfin, des complexes chiraux d’or coordinés par des ligands hélicéniques-NHC ont été préparés. Pendant ce projet, les propriétés électroniques (sigma-donatrice et pi-acceptrice) d’un carbène hélicénique ont été quantifiées
My PhD work was dedicated to the synthesis and the study of novel chiral transition metal complexes (rhenium, iridium, copper, gold) bearing NHC-helicenes ligands and to the study of their chiroptical and photophysical properties. The first subject focused on the preparation and the study of CP-phosphorescent complexes of cyclometalated rhenium(I) complexes bearing NHC-helicenic (N^C:) ligands. The influence of the ligand design, ancillary ligands and geometry of the complexes on the chiroptical and photophysical properties has been highlighted. In the second project, we have prepared novel chiral cyclometalated iridium complexes bearing one or multiple N-[6]helicenyl- benzimidazolylidene ligands.Then, the attention has been focused on monodentate complexes. Thus, in the third project, a chiral copper complex bearing a helicenic-NHC ligand which emits circularly polarized fluorescence was successfully obtained. Finally, chiral monodentate helicenic-NHC gold(I) complexes have been prepared. During this project, the electronic properties (sigma-donating et pi-accepting) of a helicenic-NHC were investigated

Chapter one introduces N-heterocyclic carbenes (NHCs) and discusses their use as ligands for rare earth metal complexes, with particular emphasis upon compounds synthesised from 2009 until the present day. Chapter two details the synthesis and characterisation of the homoleptic scandium-NHC complex [Sc(L)3] (L = [OCMe2CH2(1-C{NCHCHNiPr})]). Reactions of [Sc(L)3] with boranes, CO2 and CS2 are described which exploit the relative lability of the Sc–Ccarbene bond and allow formation of [Sc(L)2(OCMe2CH2(1-B'C{NCHCHNiPr}))] (B' = 9-BBN, BPh3, B(C6F5)3, BH3), [Sc(OCMe2CH2(1-O2CC{NCHCHNiPr})3]n, [Sc(L)2(OCMe2CH2 (1-S2CC{NCHCHNiPr})] and [Sc(L)(OCMe2CH2(1-S2CC{NCHCHNiPr})2]2. The chapter also discusses the reactivity of [Sc(L)3] towards substrates containing acidic C–H and N–H bonds and substrates containing polar E–X bonds (where E = C, Si, B, P and X = Cl, I). Chapter three describes the synthesis and characterisation of the NHC substituted scandium benzyl complexes [Sc(Bn)2(L)]2 and [Sc(Bn)(L)2], and the attempted synthesis of NHC substituted scandium aminobenzyl complexes. The reactivity of [Sc(Bn)2(L)]2 with RX substrates (R = alkyl) is discussed in detail; depending on the nature of the alkyl group, these reactions can allow formation of R–Bn , the result of carbon-carbon coupling. The complex [Sc(Bn)(L)Cl]2 has been isolated from these reactions and is structurally characterised. The reactivity of [Sc(Bn)2(L)]2 towards C–H bonds is explored and attempts to prepare NHC substituted scandium hydrides are described. Comparisons of the relative stability and reactivity of [Sc(Bn)2(L)]2 and [Sc(Bn)3(thf)3] are drawn. Chapter four documents the synthesis and characterisation of [Sc(Odtbp)2(L)] (Odtbp = 2,6-di-tert-butylphenoxide), [Sc(Odtbp)(L)2], and the samarium analogue [Sm(Odtbp)(L)2]. The reactivity of these complexes towards various small molecules is described. The chapter also details attempts to prepare the cationic scandium complexes [Sc(L)2][Bort] (Bort = bis[3,3',5,5'-tetra-(tert-butyl)-2,2-diphenolato]borate) and [Sc(L)2][B(Ph)4]. Chapter five provides overall conclusions to the work presented in this thesis. Chapter six contains all experimental and characterising data for the complexes and reactions detailed in this work.

The syntheses, structures, photophysical properties and applications of three types of photoluminescent organoplatinum(II) complexes containing N-heterocyclic carbene (NHC) ligands are described. The tetradentate dianionic bis(phenolate-NHC) type ligands provide a superior scaffold for constructing thermally stable and efficient deep-blue phosphorescent Pt(II) complexes with λmax of ~440-460 nm and solid-state emission quantum yields of ~30%. Highly efficient blue OLEDs with CIEx, y of (0.19, 0.21) were fabricated based on these emitters with maximum brightness, peak current efficiency and power efficiency of ~9500 cd m^(-2), 24 cd A^(-1) and 17 lm W^(-1), respectively. Structural modification by extending the π-conjugation of the tetradentate bis(phenolate-NHC) ligand leads to strongly phosphorescent platinum(II) complexes with long-lived emissive electronic states that can be used as a luminescent sensor for oxygen. DFT/TDDFT calculations and time-resolved spectroscopic characterizations were performed to gain insight into the structure-photophysics correlation. The N-heterocyclic carbene (NHC) ligand was incorporated into Pt(II) complexes containing tridentate deprotonated 1,3-bis(2-pyridyl)benzene (N^C^N) type ligand. In addition to the [(N^C^N)Pt(NHC)]PF6 type complexes with (N^C^N) in η3-tridentate coordination mode, Pt(II) complexes with η2-bidentate (N^CN) ligands, namely [(N^CN)Pt(NHC)2]PF6, have been isolated and structurally characterized. The highly phosphorescent [(N^C^N)Pt(NHC)]PF6 complexes were used for solution-processed green OLEDs fabrication. The peak current efficiency of 12.5 cd A^(-1) and maximum brightness higher than 2000 cd m^(-2) were achieved. The presence of the pendent pyridyl motif causes quenching of emission of the [(N^CN)Pt(NHC)2]PF6 complexes in solution at room temperature. Turning on solid-state emission of [(N^CN)Pt(nBu2Im)2]PF6 in the presence of an acidic vapor revealed its potential as a luminescent chemosensor. A class of dicationic platinum(II) terpyridyl complexes containing NHC ligand, namely [Pt(tpy)(NHC)](PF6)2, has been synthesized and structurally characterized. Even in the presence of the strong σ-donating NHC ligand, these complexes are non- or weakly emissive in solution at room temperature. However, this class of complexes displays intense emissions in solid state (298 K and 77 K), in glassy solution (77 K butyronitrile) and in PMMA (2 wt.%, 298 K). The ligand (terpyridine) displacement reaction arising from CN attack onto the Pt(II) center has been observed for [Pt(tpy)(nBu2Im)](PF6)2 leading to its application as a chemodosimeter for selective cyanide sensing in aqueous solution.
published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy

The work described herein focuses on the synthesis and characterisation of copper(I) complexes bearing N-heterocyclic carbene (NHC) ligands, their use in catalysis as well as organometallic synthesis and related reaction mechanisms. Two classes of complexes were considered: neutral NHC-Cu(I) species and their cationic analogues. Concerning the former, initial efforts were focused on the development of a general and straightforward synthetic methodology towards complexes of the type [Cu(X)(NHC)] (X = Cl, Br, I). More than 10 NHC-Cu(I) species were synthesised in high yields under mild conditions, in air and using technical grade solvents. These complexes exhibited interesting activity in the catalytic dehydrogenation of formic acid/amine adducts proving in three times more efficiency than the copper salts previously employed in such a reaction. Hydroxide- and tert-butoxide analogues showed to be efficient catalysts in the N-methylation of amines with CO₂ as carbon source, and in the dehydrogenative coupling of silanes and carboxylic acids. Experimental and computational work were carried out in order to elucidate the mechanism of these transformations. Regarding the use of these species in organometallic synthesis, homo- and heteroleptic bis-NHC-Cu(I) complexes were employed as carbene transfer reagents to other transition metals. Aside from well-known cationic gold(I) species, two novel palladium(II) analogues were isolated and fully characterised.

This thesis describes the synthesis, characterisation and reactivity of new manganese and rhenium(I) NHC complexes, which have been investigated both thermally and photochemically and the results contrasted with existing phosphine analogues in the literature. Cp’Mn(CO)2(NHC) (NHC = IEt2Me2 1, IMes 2, IiPr2Me2 3 and IPr 4) were synthesised and investigated by TRIR spectroscopy. Loss of CO was observed after 355 nm irradiation to form agostically stabilised intermediates, which reformed the parent species by recombination with CO on the nanosecond timescale. Loss of NHC was not observed, in contrast to Cp’Mn(CO)2(PPh3) which lost both CO and PPh3 upon photolysis. [Re(NHC)(Bpy)(CO)3]BAr4F (NHC = IEt2Me2 5, IMes 6) were synthesised and investigated by TRIR spectroscopy and UV/Vis absorption and emission spectrometry. Inclusion of an NHC altered the excited state manifold of the complexes, favouring population of the 3MLCT over the 3IL excited state. The lowest energy excited state for both 5 and 6 proved to be a 3MLCT excited state at 298 and 77 K. In contrast, [Re(PPh3)(Bpy)(CO)3]BAr4F exhibited 3MLCT at 298 K, but 3IL at 77 K. A series of complexes, M(NHC)(CO)4X and M(NHC)2(CO)3X (M = Re, X = Cl; M = Mn, X = Br) formed upon reaction of the corresponding M(CO)5X species and free NHC. The substitution pattern was dictated by the steric bulk of the NHC. Generation of the corresponding cations by halide abstraction was investigated. M(NHC)2(CO)3X was found to form agostic stabilised species upon halide abstraction by NaBAr4F in CH2Cl2. Under the same conditions, Re(IPr)(CO)4Cl was found to form the dichloromethane complex, [Re(IPr)(CO)4(η1-CH2Cl2)]BAr4F. In C6H5F solution under an atmosphere of dihydrogen, the CH2Cl2 ligand could be displaced by H2 to form the dihydrogen species, [Re(IPr)(CO)4(H2)]BAr4F.

Lo scopo del seguente lavoro di tesi è la sintesi e lo studio di nuovi leganti chirali N-eterociclici ad anello espanso derivanti dal diacido canforico. Lo sviluppo di nuovi leganti chirali nasce dalla possibilità di utilizzo in catalisi enantioselettiva. Questa tipologia di leganti sono facilmente sintetizzati dal diacido canforico utilizzando diverse vie di sintesi. La via di sintesi utilizzata permette di ottenere facilmente una funzionalizzazione asimmetrica. Il legante è stato studiato nella sintesi di un nuovo complesso chirale di Pd(II) utilizzando diverse condizioni di reazione. Inoltre, sono state studiate numerose vie di sintesi per nuovi leganti utilizzando i precursori dei leganti e due diversi epossidi. The aim of my training period has been the synthesis of new chiral N-heterocyclic carbene precursors starting from camphoric acid. The development of new chiral ligands starts from their possible use in new catalytic systems for enantioselective transformations. These kinds of ligands are easily synthetized from camphoric acid following different strategies. The synthetic pathway used makes simple the asymmetric functionalization. The ligand was employed in the synthesis of a new complex of Pd(II) in different conditions. In addition, numerous synthetic pathways have been investigated for new ligands using their precursors and two different epoxides.

Chapter one is an introduction, outlining the structure and bonding of N-heterocyclic carbenes (NHCs). It then goes on to give examples of f -metal NHC complexes and describes any reactivity or catalytic activity. Chapter two describes the synthesis of the transition metal NHC complexes [Fe (LMes)2] 3 and [Co(LMes)2] 4 (LMes = OCMe2 CH2(1-C{NCH2CH2NMes})). The heterobimetallic complexes [(LMes)Fe(μ-LMes)U(μ-{N(SiMe3)Si(Me)2CH2})(N(Si Me3)2)2] 5 and [(LMes)Co(μ-LMes)U(μ-{N(SiMe3)Si(Me)2CH2})(N(SiMe3)2)2] 6 were prepared from the reaction between [({Me3Si}2N)2U(NSiMe3SiMe2CH2)] and 3 or 4, respectively. Complex 5 was also synthesised by the reaction between 3 and [U(N{SiMe3}2)2]. The diamagnetic analogue [(LMes)Zn(μ-LMes)Th(μ-{N(SiMe3)Si (Me)2CH2})(N(SiMe3)2)2] 9 was prepared from the reaction between [Zn(LMes)2] and [({SiMe3}2N)2Th(NSiMe3SiMe2CH2)]. The reactivity of 5 is discussed. When 5 was reacted with 2,6-dimethylphenyl isocyanide, [({SiMe3}2N)2U{N(SiMe3)Si(Me2)C(CH2)N(2,6−Me−C6H3)}] 8 was isolated. The reaction with CO resulted in the formation of [({Me3Si}2N)2U{N(SiMe3) Si(Me2)C(CH2)CO}]. 5 showed no reactivity with azides, boranes or m-chloroperbenzoic acid and decomposed when exposed to H2, CO2 or KC8. The reaction between 6 and 2,6-di-tert-butylphenol formed the previously reported monometallic complex [({SiMe3}2N)2U(OC6H3tBu2)]. The serendipitous synthesis of the iron ate complex [Na(Fe{LMes}2)2]+ [Fe(ArO)3]– 10 (Ar = 2,6-tBu-C6H3) is also described. Chapter three describes the synthesis of the aryloxide complexes [HC(3-tBu-5-Me- C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2O)Co(THF)]2 11 and [HC(3- tBu-5-Me-C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2O)Zn(THF)n] 13. Treatment of 11 with pyridine N-oxide resulted in the formation of the pyridine-Noxide adduct [HC(3-tBu-5-Me-C6H2OH)(3-tBu-5-Me-C6H2O)μ-(3-tBu-5-Me-C6H2 O)Co(C5H5NO)]2 12. When 11 was treated with [({Me3Si}2N)2U(NSiMe3SiMe2C H2)], no reaction occured at room temperature but at 80◦C decomposition occured. When 11 was treated with [(NH4)2Ce(NO3)6] the protonated proligand HC(3-tBu- 5-Me-C6H2OH)3 reformed. The reactivity of 11 with [({Me3Si}2N)Ce(LiPr)2] is also discussed. Chapter three also discusses the preparation of the heterobimetallic complex [HC(3- tBu-5-Me-C6H2O)2-μ-(3-tBu-5-Me-C6H2O)KCo]2 14 and the salt-elimination chemistry of the complex. The preparation of [HC(3-tBu-5-Me-C6H2O)2-μ-(3-tBu-5- Me-C6H2O)KZn]2 15 is also outlined. Chapter four discusses the reactivity of [Ce(LiPr)3] (Li Pr =OCMe2CH2(1-C{NCHC HNiPr})) in C-H and N-H activation and as a catalyst for organic reactions. [Ce(LiPr)3] displayed no C-H activation chemistry with RC−−−CH (R = SiMe3, Ph, tBu), diphenyl acetone, indene or fluorene. [Ce(LiPr)3] also showed no N-H activation chemistry with pyrrole or indole, nor did it react with the lignin model compound PhOCH2Ph. When treated with an excess of benzyl chloride, [Ce(LiPr)3] underwent ligand decomposition to form the acylazolium chloride [(C6H5C(O))OCMe2CH2(1-C(C6H5C (O)){NCHCHNiPr})]Cl 18 and CeCl3. When [Ce(LiPr)3] was added to a mixture of benzaldehyde and benzyl chloride, as a coupling catalyst, the complex decomposed. [Ce(LiPr)4] was tested as a catalyst from the benzoin condensation and for the coupling of benzalehyde and benzyl chloride, however, it resulted in the decomposition of [Ce(LiPr)4]. Chapter four also outlines the catalytic activity of 3. The complex showed no reactivity as a hydrogenation catalyst towards alkenes, aldehydes or ketones but did display reactivity as a hydroboration catalyst for alkenes, aldehydes or ketones. Chapter five presents the conclusions for chapters two to four. The final chapter contains the experimental details from the previous chapters.

The versatility of N-heterocyclic carbenes (NHCs) is demonstrated by numerous practical applications in homogeneous transition metal catalysis, organocatalysis and materials science. There remains a paucity of electropositive metal NHC complexes and so this chemistry is poorly developed with respect to that of the late transition metal and main group elements. This thesis describes the synthesis of new alkoxy-tethered NHC proligands, their use in the synthesis of reactive metal amide and metal alkyl complexes, and finally small molecule activation using these complexes. Chapter One introduces NHCs and discusses their use as supporting ligands for early transition metal and f-block complexes. Small molecule activation using organometallic complexes is examined alongside the use of electropositive metal NHC complexes in catalysis. Chapter Two contains the synthesis and characterisation of new alkoxy-tethered NHC proligands and a variety of electropositive MII (M = Mg and Zn), MIII (M = Y, Sc, Ce and U) and MIV (M = Ce and U) amide complexes. X-ray diffraction studies and a DFT study are used to probe the extent of covalency in the bonding of the MIV complexes. Chapter Three investigates the reactivity of the amide complexes prepared in Chapter Two. The MII complexes are shown to be initiators for the polymerisation of raclactide into biodegradable polymers. The MIII complexes are used to demonstrate additionelimination reactivity of polar substrates across the M-Ccarbene bond which allows the formation of new N-E (E = Si, Sn, P or B) bonds. Treatment of the UIII silylamide complex U(N{SiMe3}2)3 with CO results in the reductive coupling and homologation of CO to form an ynediolate core -OC≡CO- and the first example of subsequent reactivity of the ynediolate group. The MIV complexes are used to examine the potential for forming MIV cationic species and alkyl complexes. Chapter Four examines the synthesis of MIII (M = Ce and Sc) aminobenzyl complexes and MIII (M = Y, Sc and U) neosilyl and neopentyl alkyl complexes. The addition-elimination reactivity discussed in Chapter Three is extended to include C-E bond formation (E = Si, Sn, P, B, I or C). Chapter Five provides overall conclusions to the work presented within this thesis. Chapter Six gives experimental and characterising data for all complexes and reactions in this work.

Le sujet de cette thèse porte sur l’étude de ligands hybrides incorporant un donneur carbène N-hétérocyclique (NHC). Les ligands phosphine-NHC construits sur le motif m-phénylène ont conduit à des complexes di- ou tétranucléaires d’Ag, Cu, Au et Ir, et à des complexes bimétalliques Ag/Cu et Ag/Ir par transmétallation sélective du site NHC. Dans le cas des ligands phosphino-picoline-NHC (PNC), la transmétallation des sels de Li ou K correspondants a permis d’isoler des complexes « pinceurs » dé-aromatisés du Cr, Fe et Co. La déprotonation du ligand bis(phosphinométhyl)pyridine (PNP) a été examinée, et les ligands dé-aromatisés mono- et bis-anioniques correspondants ont été utilisés dans des réactions de transmétallation vers le Cr(II) et Zr(IV). Différents modes de coordination des ligands dé-aromatisés, notamment une métallation de la position alpha-CHP, ont été observés. La substitution de la phosphine dans PNC par une fonction imine conduit à un ligand hybride « rédox non-innocent »
The purpose of this work is the synthesis and study of hybrid and potentially “pincer” ligands featuring an N-heterocyclic carbene (NHC) donor. The phosphine-NHC ligands based on the m-phenylene framework led to di- or tetranuclear Ag, Cu, Au and Ir complexes, and to bimetallic Ag/Cu and Ag/Ir complexes by selective transmetallation of the NHC. With the phosphino-picoline-NHC (PNC) ligands, transmetallation from the corresponding Li or K salts led to dearomatised Cr, Fe and Co “pincer” complexes. Deprotonation of the bis(phosphinomethyl)pyridine (PNP) ligand was also examined. The corresponding dearomatised mono- and bis-anionic ligands were isolated as Li or K salts and further used in transmetallation reactions towards Cr(II) and Zr(IV). Different coordination modes of the dearomatised ligands, including side-arm metallation, were observed. Substitution of the phosphine group in PNC by an imine donor led to a hybrid and “redox non-innocent” ligand

The aim of my training period has been the synthesis of new chiral N-heterocyclic carbene precursors starting from camphoric diacid and the employment of imidazolium salts derived NHC as linker to dendrimers supports for organometallic catalysis. New chiral ligands are needed to develop new catalytic systems for enantioselective transformations. The new type of ligand described was developed starting from camphoric diacid, a cheap chiral molecule, following different synthetic strategies. Asymmetric functionalized chiral NHCs are readily available by methods developed and two of the precursors obtained were employed in preliminary tests with Aluminium and Palladium. An NHC derived from imidazolium salt has been investigated as linker to dendrimeric supports for tetraarylciclopentadienone-Ruthenium complexes with the aim to combine advantages of homogeneous catalysis to advantages of heterogeneous one, in particular easy recover of catalyst. The functionalized dendrimers obtained have been used in transfer hydrogenation and dehydrogenation reactions. Moreover a new class of functionalized dendrimer was obtained employing a new tetraarylciclopentadienone-Ruthenium complex with trimethyl silyl groups on cyclopentadienone ligand with the aim to change solubility of the system.

N-heterocyclic carbenes (NHCs) have emerged as appropriate replacements for phosphines to synthesized highly active metal complexes in homogeneous catalysis. The advantages of NHCs over phosphines include ease of handling, minimal toxicity and powerful electron donating properties. They bind transition metals with no need of back-donation and yield complexes with enhanced stability. The ability of NHCs to bind all metals from the periodic table, in low and high oxidation states, creates an unprecedented opportunity for the design of new complexes. This dissertation is dedicated to the synthesis of well-defined organosilver and organogold complexes bearing NHC ligands. In addition, two short chapters describe briefly the synthesis of NHC acetylacetonate palladium(II) complexes, and the use of NHC ruthenium(II) indenylidene complexes in ring opening metathesis polymerization reactions. New silver(I) and gold(I) halide mono-NHC complexes are synthesized, structurally characterized, and compared to other existing silver(I) and gold(I) complexes. The silver cation trends to form thermodynamically favored bis-NHC complexes and the success for the synthesis of kinetically favored silver(I) mono-NHC complexes is strongly dependant of the carbene, the solvent, and the silver salts used. In contrast, the synthesis of gold(I) mono-NHC complexes appears easier specially by transmetalation starting from silver(I) NHC complexes. The reactivity of both metals NHC complexes is directly related to the strength of the metal-carbene bond. The gold(I) cation firmly bound to the carbene, undergoes oxidative addition with halogens to afford gold(III) NHC complexes, or dehalogenation in presence of inorganic silver salts to afford cationic gold(I) mono-NHC complexes in coordinating solvent. The coordinating solvent can be replaced by a neutral or anionic group to yield gold(I) NHC complexes with unusual ligands such as olefins, pyridines, sugars. In contrast, the silver(I) cation is weakly bound to the carbene, and silver(I) NHCs decompose in presence of halogens or inorganic silver salts. In conclusion the synthesis of the NHC complexes emphasizes deeply the similarities and the differences between silver and gold chemistries. While NHCs ideally stabilize gold(I) and(III) complexes, phosphines appears to be a more promising alternative than NHCs for the chemistry of silver.

Cette dissertation est dédiée à la synthèse de complexes organométalliques d’argent et d’or portant des ligands NHC et ayant une structure bien définie. Par ailleurs, deux courts chapitres traitent brièvement de la synthèse de complexes NHC d’acétylacétonate de palladium(II), et de l’utilisation de complexes NHC d’indénylidène de ruthénium(II) pour catalyser des réactions de polymérisation par métathèse par ouverture de cycle (ROMP). L’or(I) qui est fortement complexé au carbène subit une réaction d’addition oxydante en présence d’halogènes pour donner des complexes NHC d’or(III), ou encore une déshalogénation en présence de sels d’argent inorganiques pour donner des complexes mono-NHC cationiques d’or(I) dans des solvants coordinants. Ce solvant coordinant peut être remplacé par un ligand neutre ou anionique et générer des complexes NHC d’or(I) avec des ligands peu courants tels que des oléfines, des pyridines, ou même des sucres. En revanche, le cation argent(I) est faiblement complexé au carbène, et les complexes NHC d’argent(I) se décomposent en présence d’halogènes ou de sels d’argent inorganiques
This dissertation is dedicated to the synthesis of well-defined organosilver and organogold complexes bearing NHC ligands. In addition, two short chapters describe briefly the synthesis of NHC acetylacetonate palladium(II) complexes, and the use of NHC ruthenium(II) indenylidene complexes in ring opening metathesis polymerization reactions. New silver(I) and gold(I) halide mono-NHC complexes are synthesized, structurally characterized, and compared to other existing silver(I) and gold(I) complexes. The gold(I) cation firmly bound to the carbene, undergoes oxidative addition with halogens to afford gold(III) NHC complexes, or dehalogenation in presence of inorganic silver salts to afford cationic gold(I) mono-NHC complexes in coordinating solvent. The coordinating solvent can be replaced by a neutral or anionic group to yield gold(I) NHC complexes with unusual ligands such as olefins, pyridines, sugars. In contrast, the silver(I) cation is weakly bound to the carbene, and silver(I) NHCs decompose in presence of halogens or inorganic silver salts

Reproduction de : Thèse de doctorat : chimie et physico-chimie des polymères : Le Mans : 2007. Reproduction de : Thèse de doctorat : chimie : La Nouvelle-Orléans : 2007.
Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre.

Les carbènes N-hétérocycliques (NHC) sont très utilisés pour complexer les métaux de transition. Ils quittent rarement ce rôle de ligand ancillaire et trouvent, depuis une vingtaine d’années, des applications en catalyse ou, plus récemment, en chimie médicinale. Dans ce travail, nous discuterons d’une méthode de synthèse douce conduisant à la formation de complexes AgI – NHC via une source d’argent soluble. Cette méthode nous a permis d’obtenir des complexes bien connus mais également d’accéder à une nouvelle série de complexes NHC-Ag-phosphine. Nous présenterons également une nouvelle réaction où des NHC portant une fonction azoture à proximité du carbone du carbène quittent leur rôle de ligand ancillaire et conduisent à la formation d’hétérocycles azotés par cyclisation carbène-nitrène. Cette réaction sera présentée en détail, ainsi que la caractérisation spectroscopique concernant une sous-série de composés fluorescents obtenus par cette méthode. Enfin, nous présenterons une stratégie de post-fonctionnalisation de complexes développée dans notre équipe. Des complexes argent(I)-NHC portant un azoture proches du centre carbénique catalysent leur propre fonctionnalisation. De plus, des complexes de cuivre(I) portant des azotures en position éloignée du centre métallique seront greffés sur des nanoparticules magnétiques pour servir de catalyseur recyclables
N-heterocyclic carbenes (NHC) are widely used to complex transition metals. They rarely leave their role as ancillary ligand and find, since 20 years, applications in catalysis or, more recently, in medicinal chemistry. In this work, we will discuss a mild synthetic method leading to the formation of AgI – NHC complexes via a soluble silver species. This method allowed us to obtain well known complexes but also to access a new series of NHC-Ag-phosphine complexes. We will also present a new reaction where NHC ligands bearing an azide function close to the carbenic center leave their role as ancillary ligand and lead to the formation of nitrogen rich heterocycles by a carbene-nitrene cyclization. This reaction will be presented in detail, along with the spectroscopic characterization regarding a sub-series of fluorescent compounds obtained by this method. Finally, we will present a post-functionalization strategy of complexes developed in our team. Silver(I)-NHC complexes tagged by an azide close to the carbenic center catalysed their own functionalization. Moreover, copper(I) complexes tagged by an azide function in a distant position from the metallic centre will be grafted on magnetic nanoparticles to act as recyclable catalysts

L’objectif de cette thèse portait sur la synthèse de complexes portant un ligand NHC associé à une fonction oxygénée et à leur application en catalyse d’oligomérisation de l’éthylène. Dans le but de synthétiser des complexes avec des ligands NHCalcool, les complexes d’argent correspondants ont été synthétisés et utilisés en transmétallation. Aucun résultat concluant n’a pu être obtenu avec le nickel à cause de l’acidité du proton alcoolique. Mais un ligand NHC-alcoolate a pu être obtenu par déprotonation directe du pro-ligand avec une base forte. Il fut alors possible d’accéder à des complexes de nickel polynucléaires, certains incorporant dans leur structure des cations lithium provenant de la base utilisée. Par comparaison, des complexes de palladium ont été synthétisés avec des NHCs-alcool ou -alcoolate par réaction des pro-ligands avec Pd(acac)2 suivie de réactions acido-basiques. Etant donné la difficulté d’obtention des complexes de nickel avec des ligands NHC-alcool, la fonction éther a été étudiée. Les complexes résultants ont été testés en oligomérisation de l’éthylène
The purpose of this work was the synthesis of complexes bearing O-functionalized NHC ligands in order to test their catalytic properties in ethylene oligomerization. In order to have access to alcohol-functionalized complexes, the corresponding silver complexes were synthesized for transmetallation purpose. Whereas no concluding results were obtained with the alcohol function in association with nickel, it was possible to access an alcoholate-functionalized NHC ligand by deprotonation of the corresponding pro-ligand. Thus, polynuclear nickel complexes were prepared, some of them included in their structure a lithium cation originating from the base. For comparison, alcohol- and alcoholate-functionalized NHC palladium complexes were synthesized by direct reaction of the pro-ligand with Pd(acac)2 followed by acidobasic reactions. Because of the complexity of the chemistry of NHC-alcohol ligands associated with nickel, the ether functionality was explored. A library of nickel complexes was synthesized and tested in the catalytic ethylene oligomerization

In the last twenty years, N-heterocyclic carbenes (NHC) have gained general attention as a class of ligands alternative or complementary to the classical ones, based on phosphorous (phosphines, phosphites, etc.) or nitrogen (amines, imines, etc.) donor atoms. In particular, a growing number of new technological applications based on Au(I)- or Au(III)-NHC complexes has appeared. Noteworthy, up to now the majority of these examples deals with N-heterocyclic monocarbene gold complexes. This PhD thesis is focused on the chemistry of gold complexes with di(NHC) ligands (di(NHC) = di(N-heterocylic carbene)) with particular reference to their synthesis and to the determination of a possible relation between their structure, properties and reactivity. In particular the obtained results are divided in three main chapters: i) Synthesis and characterization of the gold(I) di(NHC) complexes; ii) Oxidation of the gold(I) di(NHC) complexes; iii) Synthesis and reactivity of silver and gold complexes with novel di(NHC) ligands obtained via click reaction. i) Synthesis and characterization of the gold(I) di(NHC) complexes. Gold(I) complexes with different functionalized N-heterocyclic di(NHC) ligands have been prepared by direct deprotonation of the diimidazolium salts, that are the di(NHC) ligand precursors, in the presence of AuCl(SMe2) and of a mild base (NaOAc). In the adopted synthetic conditions, dinuclear dicationic gold(I) complexes presenting a metallamacrocyclic structure with two bridging di(NHC) ligands have been obtained in good yields. The photoluminescence and electrochemical properties of the synthesized complexes are strongly influenced by the structure of the di(NHC) ligand employed, in particular by the bridge present between the two imidazole-2-ylidene rings. Remarkably we identified complex 3 (Y = (CH2)3) as a very strong solid state emitter with an almost unitary quantum yield of emission (Фem = 96 %). The ligands of complex 3 were functionalized with different wingtip substituents, bearing long aliphatic chains of different length, with the aim of obtaining luminescent liquid crystals. The new complexes of this type behave as thermotropic materials, differing from the parent compound 3. ii) Oxidation of the gold(I) di(NHC) complexes. The reactivity of the gold(I) complexes toward oxidative addition of halogen is strongly influenced by the employed halogen and by the structure of the di(NHC) ligand. In general stable Au(III)/Au(III) complexes were obtained; however with the bulkier iodine a mixed valence Au(I)/Au(III) complex is isolated. Moreover the presence of the propylene bridge in the di(NHCs) favors the formation rather novel Au(II)/Au(II) complexes. The nature and the geometry of the obtained products have been fully elucidated in several cases by X-ray analysis. iii) Synthesis and reactivity of silver and gold complexes with novel di(NHC) ligands obtained via click reaction. The copper(I) catalyzed azide alkyne cycloaddition was used to introduce new functionalities (benzyl or polyethyleneglycole chain substituted triazole) on the peripheral positions of the bis(1-methylimidazole)propane core. Using the optimized reaction condition it was possible to prepare the corresponding gold(I) and gold(III) complexes. The in vitro cytotoxic activity of the functionalized gold(III) di(NHC) complexes was evaluated on a series of different neoplastic cell lines and on two healthy cell lines; The functionalized complexes are more active than the parent unfunctionalized ones and they express cytotoxicity preferentially towards the neoplastic cells.
Negli ultimi vent’anni i leganti carbenici N-eterociclici (NHC) sono stati una delle classi di leganti più studiate in chimica organometallica. Questi leganti si sono infatti imposti come valida alternativa ai classici leganti σ-donatori basati su atomi donatori quali fosforo (fosfine, fosfiti, ecc.) e azoto (ammine, immine, ecc.). In particolare in letteratura si riscontra un numero sempre crescente di lavori riguardo nuove applicazioni tecnologiche di complessi di oro(I) e oro(III) con leganti NHC. Ad oggi, la maggior parte di questi esempi riguarda complessi di oro con leganti mono(carbenici N-eterociclici). Il lavoro svolto in questa tesi di dottorato è invece incentrato sulla sintesi e caratterizzazione di nuovi complessi di oro con leganti di(NHC) (di(NHC) = di(carbene N-eterociclico)) e sulla ricerca di una possibile relazione tra la loro struttura molecolare, le loro proprietà e la loro reattività. I risultati ottenuti sono divisi in tre capitoli principali: i) Sintesi e caratterizzazione di nuovi complessi di oro(I) con leganti di(NHC); ii) Ossidazione dei complessi di oro(I) con leganti di(NHC); iii) Sintesi e reattività di complessi di oro e argento con nuovi leganti di(NHC) funzionalizzati mediante click chemistry. i) Sintesi e caratterizzazione di nuovi complessi di oro(I) con leganti di(NHC). Nuovi complessi di oro(I) con leganti di(NHC) differentemente funzionalizzati sono stati ottenuti mediante deprotonazione diretta dei corrispondenti sali di diimidazolio, precursori dei leganti carbenici, in presenza di AuCl(SMe2) e di una base debole (NaOAc). Nelle condizioni di reazione impiegate sono stati ottenuti, con buone rese, complessi dinucleari di oro(I) caratterizzati da una struttura metallamacrociclica con due leganti di(NHC) a ponte fra i due centri metallici. Le proprietà fotochimiche ed elettrochimiche dei complessi di oro(I) ottenuti sono fortemente influenzate dalla struttura del legante di(NHC) utilizzato e in particolare, dal ponte (Y) presente tra i due anelli imidazol-2-ilidenici. È stato identificato un complesso (3, Y = (CH2)3) caratterizzato da una fotoemissione allo stato solito molto intensa con una resa quantica di emissione quasi unitaria (Фem = 96 %). Il legante di(NHC) presente nella struttura del complesso 3 è stato successivamente funzionalizzato sugli atomi di azoto in posizione 1,1’ con sostituenti contenenti catene alifatiche di diversa lunghezza con l’obiettivo di ottenere complessi con caratteristiche di cristalli liquidi luminescenti. I nuovi complessi ottenuti, a differenza del complesso di riferimento 3, si comportano come materiali termotropici. ii) Ossidazione dei complessi di oro(I) con leganti di(NHC). La reattività dei complessi di oro(I) nella reazione di addizione ossidativa di alogeno è fortemente influenzata dall’alogeno e dalla struttura del legante di(NHC) impiegati. Nella maggior parte dei casi sono stati ottenuti complessi dinucleari di oro(III) stabili; tuttavia utilizzando come ossidante un alogeno relativamente ingombrante come lo iodio è stato possibile isolare anche un complesso a valenza mista Au(III)/Au(I). Inoltre la presenza del ponte propilene nella struttura dei complessi di(NHC) favorisce la formazione di complessi in cui l’oro è presente nel poco comune stato di ossidazione Au(II)/Au(II). La struttura e la geometria dei prodotti ottenuti è stata in molti casi confermata dalla risoluzione della relativa struttura ai raggi X. iii) Sintesi e reattività di complessi di oro e argento con nuovi leganti di(NHC) funzionalizzati mediante click chemistry. La reazione di cicloaddizione tra azide e alchino catalizzata da sali di Cu(I) (CuAAC) è stata utilizzata per introdurre nuovi gruppi funzionali (anelli triazolici recanti rispettivamente un gruppo benzile o una catena di polietilenglicole) nelle posizioni 5,5’ degli anelli imidazolici del precursore carbenico a ponte propilenico. Utilizzando le condizioni di reazione ottimizzate è stato quindi possibile ottenere i corrispondenti complessi dinucleari di oro(I), oro(III) e argento(I). L’attività citotossica in vitro dei complessi di oro(III) con leganti di(NHC) funzionalizzati è stata determinata su una serie di differenti linee cellulari neoplastiche e su due linee cellulari sane. I complessi funzionalizzati presentano un’attività maggiore rispetto ai complessi con leganti non funzionalizzati ed esprimono la loro citotossicità in maniera preferenziale verso le cellule tumorali.

Les performances des catalyseurs à base de palladium dans diverses réactions de couplage croisé ont suscité un intérêt croissant depuis les années soixante-dix et le développement de versions énantiosélectives a fait l’objet de recherches intensives. Dans ce domaine, les ligands auxiliaires N-hétérocycliques carbènes (NHCs) monodentates possédant de bonnes propriétés σ donneur et π-accepteur confèrent au métal d’excellentes réactivités. Les ligands NHCs sont appelés ligands intelligents, car leurs propriétés électroniques et stériques peuvent être finement ajustées à des transformations catalytiques spécifiques. Par conséquent, les complexes chiraux NHC-Pd sont une classe de catalyseurs chiraux qui se sont développés rapidement au cours des dernières décennies. Néanmoins, de nouveaux catalyseurs avec une réactivité et une énantiosélectivité améliorées sont nécessaires car seules quelques applications sont réellement développées dans l’industrie. L’objectif de mon doctorat était d’étudier un nouveau concept de complexes chiraux NHC-Pd et leurs applications pour explorer de nouvelles transformations catalytiques. Le premier chapitre expose la chimie du carbène en tant que ligands des métaux de transition avec les principales réalisations décrites dans la littérature. Les propriétés chimiques des NHCs sont également brièvement présentées. Dans ce chapitre, les différents designs de ligands chiraux NHC pour la catalyse à base de palladium sont résumés ainsi que les applications dans la catalyse énantiosélective. Enfin, des études antérieures sur les complexes chiraux NHC-palladium réalisées dans notre laboratoire sont présentées afin de définir les objectifs et les enjeux de mon travail de doctorat. Dans le deuxième chapitre de ce manuscrit, nous analysons les avantages et les inconvénients des catalyseurs développés dans notre groupe, afin de simplifier les étapes de synthèse et d’améliorer l’activité catalytique. En conséquence, certains nouveaux complexes NHC-avec chiralité axiale ont été conçus et synthétisés par des méthodologies de synthèse décrites dans la littérature. Les complexes chiraux de palladium possédants un NHC de symétrie C2 ont été d’abord préparés puis les diastéréoisomères ont été purifiés par chromatographie sur colonne de gel de silice pour éliminer les composés méso. Par la suite, les complexes hétérochiraux ont été résolus par HPLC chirale à l’échelle préparative pour les obtenir sous forme énantiomériquement pure. Enfin, la réactivité catalytique et l’induction énantiomérique que permet d’atteindre ces catalyseurs Pd-NHC-chiraux ont été évaluées dans une réaction modèle : l’α-amide arylation d’amides. De très bonnes inductions chirales ont été atteintes.Dans le troisième chapitre, de nouvelles transformations catalysées par le palladium ont été conçues et étudiées avec les nouveaux complexes chiraux-NHC précédemment établis en laboratoire. Après une étape d’optimisation des conditions de réaction et le criblage de plusieurs catalyseurs, nous avons constaté que ces nouveaux catalyseurs permettent d’obtenir une bonne induction chirale dans l’α-arylation de cétones. Nous avons également essayé l’hydrogénation catalysée par des complexes Pd-NHC cependant cette réaction n’a pas conduit à des résultats notables. Les réactions de couplage de Kumada ont également été étudiées pour synthétiser des métacyclophanes possédant une chiralité planaire. Divers métacyclophanes chiraux ont été préparés et leurs stabilités de configuration ont été étudiées. Des conditions de réaction optimales ont été identifiées afin de réaliser cette réaction asymétrique avec de bons résultats en termes de réactivité et d’énantiosélectivité
The performances of palladium-based catalysts in various cross-coupling reactions have attracted an ever-growing attention since the seventies and the development of enantioselective versions was the subject of intensive research. In this field, monodentate auxiliary N-heterocyclic carbene (NHCs) ligands possessing robust σ-donating and adaptable π-accepting properties confer to the metal excellent reactivities. NHCs ligands are referred as smart ligands, because their electronic and steric properties can be finely tuned to specific catalytic transformations. Therefore, chiral NHC-Pd complexes are a class of chiral catalysts that have developed rapidly in the recent decades. Nevertheless, new catalysts with enhanced reactivity and enantioselectivities are required as only few applications are actually developed in the industry. The goal of my Ph.D. was the investigated of a new design of chiral NHC-Pd complexes and their application to explore new catalytic transformations. The first chapter is focused on carbene chemistry as ligands of transition metals with main achievements reported in the literature. Chemical properties of NHCs have been also reviewed. In this chapter, the different designs of chiral NHC ligands for palladium-based catalysis reported in the literature as well as their applications in enantioselective catalysis have been also surveyed. Finally, previous studies on chiral NHC-palladium complexes in our laboratory are presented in order to define the objectives and issues of my Ph.D. work. In the second chapter of this manuscript, we analyze the advantages and disadvantages of the catalysts developed in our group, with the goal of simplifying the synthesis steps and improving the catalytic activity. As a result, some novel NHC-Pd complexes with axial chirality were designed and synthesized by known synthetic methods. The synthesized C2-symmetric NHC-Pd complexes were first attempted to separate diastereomers by silica gel column chromatography to remove meso compounds. Subsequently, heterochiral complexes were resolved in enantiomerically pure form by preparative-scale chiral HPLC. Finally, the catalytic reactivity and enantiomeric inductions of these highly enantiomerically pure chiral NHC-Pd catalysts were evaluated in the benchmark reaction: α-amide arylation of amides. Up to good chiral inductions were reached.In the third chapter, novel palladium-catalyzed transformations were investigated and developed with the new chiral Pd-NHC complexes previously established in the laboratory. After the optimization of reaction conditions and the screening of several catalysts, we found that these new catalysts can achieve good chiral induction in the α-arylation of ketones. We also tried NHC-Pd catalyzed hydrogenation, although the reaction did not lead to noticeable results. Kumada coupling reactions were also studied to synthesize planar-chiral metacyclophanes. Various chiral metacyclophanes have been prepared and their configurational stabilities have been investigated. Finally, optimal reaction conditions have been identified allowing to carry this asymmetric reaction with good results in terms of both reactivity and enantioselectivity

Chapter one is an introduction to the less common coordination and oxidation chemistry of palladium; complexes containing Pd-OR, Pd-NR2 and those in the oxidation states of +IV. An outline of PdII/IV catalysed ligand-directed oxidative functionalisation is also included. Chapter two covers the design and synthesis of a range of tethered N-heterocyclic carbene (NHC) complexes of Pd. In addition, the syntheses of a number of new tethered NHC ligands are described. The use of Density Functional Theory (DFT) to model the complexes in this thesis was explored. Chapter three describes the synthesis and characterisation of PdIV halide complexes. The relevance of these compounds to PdII/IV catalysed ligand-directed oxidative functionalisation is explored. DFT was used to probe the reaction pathway for N-bromosuccinimide and iodobenzene dichloride. Chapter four examines reactions with oxidants used to form C-O and C-C bonds. The reaction pathway for iodobenzene diacetate was investigated using DFT. Chapter five contains experimental details and characterising data for the compounds reported.

Thesis (M.S.)--University of New Orleans, 2004.
Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Chemistry."--Thesis t.p. Vita. Includes bibliographical references.

Se ha obtenido una nueva familia de cuatro Complejos Organometálicos Supramoleculares (SOCs) basados en pireno. Dentro de los cuales se ha desarrollado un nuevo receptor de PAH, capaz de discernir entre los diferentes PAH en función de su forma, tamaño, y número de electrones-pi. Hemos desarrollado una estrategia eficiente para la extracción de PAH, que son compuestos tóxicos y carcinogénicos, en disolventes orgánicos. Paralelamente, se han obtenido dos receptores de fulereno, capaces de adaptar su tamaño a la forma del fulereno. Debido a la mayor afinidad respecto a un fulereno específico, mostramos un potencial nuevo método de purificación de fulerenos. Describimos el primer sistema host-guest utilizado como fotosensibilidazor en la generación de oxígeno singlete. Este SOC con fulereno atrapado, fue capaz de oxidar una gran variedad de alquenos utilizando el oxígeno singlete generado a partir de aire a presión atmosférica y luz visible. Finalmente se encapsularon multiples guests.
Three nickel-based and one palladium-based supramolecular organometallic cages have been prepared. These four cages are based on a N-heterocyclic carbene ligand with a pyrene tag, that has been key in the subsequent applications of the cage together with the inner cavity. By pi-stacking interactions, it has been possible to encapsulate both polycylic aromatic hydrocarbons and fullerenes. The interest on first group of compounds is based on their accurate toxicity while the fullerenes are interesting due to their added value. It was possible to extract the first group of molecules from an organic media through the encapsulation inside the supramolecular cages. The host-guest adduct formed with fullerenes encapsulated inside the palladium cage was used as photocatalyst of aromatic, cyclic and acyclic substrates via singlet oxygen generation. The same palladium cage was used as receptor for multiple stacks of polyaromatic compounds.
Programa de Doctorat en Ciències

Initially, N-heterocyclic carbene ligands (NHCs) were considered ancillary ligands alternative to more classical two-electron donor ligands, phosphorous- (phosphines, phosphites, etc) and nitrogen-based (amines, imines, etc). Nowadays their role in organometallic chemistry is pivotal, and they found application in many different fields. The Cp*Ir(III)-based complexes gained interest during the past years because they may be employed as catalysts in many organic transformations, and the inclusion of a NHC ligand in the coordination sphere of the complex generally enhanced both its robustness and catalytic activity. An appealing catalytic application of Cp*Ir(III)-NHC complexes is the water oxidation reaction, that is the oxidative half-reaction of an overall process called “artificial photosynthesis”. This is a promising route to provide, in the future, the production of green and sustainable energy alternative to the consumption of fossil fuels, and to convert solar energy into chemical one. This PhD thesis is aimed to the study of iridium(III) complexes bearing di-(N-heterocyclic carbene) ligands (di-NHC), focusing either on the synthetic aspects and on the catalytic activity. Furthermore, the evaluation of the final steric and electronic properties of the complexes deriving by changes in the structure of the di-NHC ligand, will be addressed; the final aim is to find a relationship between the structure of the ligand and the properties and catalytic behavior of the complexes. In this regard, the catalytic activity will be evaluated mainly in water oxidation reaction, but also other organic transformations will be considered (transfer hydrogenation of ketones). The obtained results will be divided in four main chapters: i] Synthesis and characterization of a series of mononuclear Ir(III) di-NHC complexes (Chapter 2); ii] Water oxidation reaction catalyzed by the mononuclear Ir(III) di-NHC complexes synthesized in the frame of the present PhD project (Chapter 3); iii] Synthesis, characterization and catalytic activity of novel dinuclear di-NHC Ir(III) complexes (Chapter 4); iv] Reactivity and coordination properties of mono- and di-NHC ligands deriving from non-classical carbene units (Chapter 5). i] Synthesis and characterization of a series of mononuclear Ir(III) di-NHC complexes. A series of novel di-NHC iridium(III) complexes, having general formula [IrClCp*(di-NHC)](PF6), have been synthesized through the transmetalation of the di-NHC moiety from pre-formed, isolated and characterized dinuclear di-NHC silver(I) complexes. In the obtained Ir(III) complexes, the di-NHC ligand is coordinated to the metal centre in chelating fashion; this has been confirmed by the determination of the X-ray crystal structure of some complexes. The optimized synthetic protocol has been extended to several di-NHC ligands having different substituents at the nitrogen atoms and length of the alkyl bridging group. The effect of the substituents on the electron density, both on the metal and the carbene carbon, has been evaluated. ii] Water oxidation reaction catalyzed by the mononuclear Ir(III) di-NHC complexes. Some of the synthesized mononuclear di-NHC complexes have been successfully employed as catalysts for the water oxidation reaction in presence of Ce(IV) (as (NH4)2[Ce(NO3)6], referred also as CAN) as sacrificial oxidant. One of the most active complexes (complex 2) has been tested also in presence of NaIO4, showing activity comparable to that reported in literature for other Ir(III)-NHC complexes. The catalyst fate under turnover conditions has been investigated by detecting the evolving gas via GC-MS measurements, and a small amount of CO2 was observed concomitantly to the O2 evolution. The amount of CO2 derives probably from the oxidative degradation of the ligand set. Complex 2 has been also employed in a photo-induced process, coupled with a photosensitizer ([Ru(bpy)3]2+) and a sacrificial acceptor of electrons (S2O82-), exhibiting activity remarkably different than that observed employing IrCl3 under the same experimental conditions. IrCl3 is a well-known precursor of IrOx nanoparticles, so the observed difference may be considered a proof of the molecular nature of the catalyst. Further investigations allowed to detect, through EPR measurements, the formation of an Ir(IV) species, which is a plausible intermediate in the catalytic cycle, confirming the molecular nature of the employed catalyst. iii] Synthesis, characterization and catalytic activity of novel dinuclear di-NHC Ir(III) complexes. Novel dinuclear di-NHC Ir(III) complexes have been synthesized employing ligand precursors having a flexible and long bridging group between the carbene units or wingtip substituents with donor functionalities. Such complexes have been fully characterized, and in the case of complex 15 the crystal structure was also obtained. Such complexes have been successfully employed as catalysts in transfer hydrogenation of ketones: a scope of substrates has been spanned, and the tested complexes, especially complex 16, showed moderate to good activity. iv] Reactivity and coordination properties of mono- and di-NHC ligands derived from non-classical carbene units. In the frame of a collaboration with the group of Prof. C. J. (Kees) Elsevier (University of Amsterdam), the possibility to obtain Ir(III) complexes with six-membered saturated NHCs was investigated. Unfortunately, the results obtained in this regard are not satisfactory, probably for the intrinsic instability of the ligand precursors and/or of the corresponding free carbenes. Furthermore, the synthesis and the reactivity of mixed NHC-MIC ligands has been successfully carried out. The synthesis of the corresponding silver(I) complexes was performed and a preliminary optimization of the transmetalation reaction conditions has been accomplished, leading to the obtainment of a novel Ir(III) complex bearing a NHC-MIC ligand.
Inizialmente, i leganti carbenici N-eterociclici erano considerati leganti ancillari alternativi ai più classici leganti donatori bielettronici al fosforo (fosfine, fosfiti, etc) e all’azoto (ammine, immine, etc). Al giorno d’oggi il loro ruolo nella chimica organometallica è invece più centrale, e complessi con leganti carbenici trovano applicazione in diversi campi. Negli ultimi anni è aumentato l’interesse verso complessi basati sul frammento Cp*Ir(III), perché possono essere utilizzati come catalizzatori in numerose trasformazioni organiche; inoltre, l’introduzione di un legante NHC nella sfera di coordinazione del complesso dovrebbe aumentare sia la sua stabilità che la sua attività catalitica. Un’interessante applicazione catalitica dei complessi Cp*Ir(III)-NHC è la reazione di ossidazione dell’acqua, che è la semi-reazione di un processo più complesso chiamato “fotosintesi artificiale”. Nell’ambito del problema globale legato alla produzione e al consumo di energia, questo processo rappresenta una possibile alternativa all’utilizzo dei combustibili fossili e in futuro potrebbe permettere la produzione di energia in modo green e sostenibile per conversione dell’energia solare in energia chimica. Questa Tesi di Dottorato ha come scopo lo studio di complessi di iridio(III) aventi nella sfera di coordinazione leganti dicarbenici N-eterociclici (di-NHC) e sarà focalizzata sia sugli aspetti sintetici che sull’attività catalitica dei complessi ottenuti. Inoltre, verranno discusse le proprietà steriche ed elettroniche dei complessi in funzione dei cambiamenti apportati alla struttura dei leganti di-NHC utilizzati; lo scopo ultimo sarà quello di trovare una relazione tra la struttura del legante, le proprietà stereo-elettroniche del complesso e la sua attività catalitica. A questo proposito, l’attività catalitica sarà principalmente valutata nella reazione di ossidazione dell’acqua, ma verranno prese in esame anche altre trasformazioni organiche (transfer hydrogenation di chetoni) I risultati ottenuti verranno divisi in quattro capitoli principali: i] Sintesi e caratterizzazione di una serie di complessi mononucleari di Ir(III) aventi un legante di-NHC nella sfera di coordinazione (Capitolo 2); ii] Reazione di ossidazione di acqua catalizzata dai complessi mononucleari di-NHC di Ir(III) sintetizzati nell’ambito di questo progetto di Dottorato (Capitolo 3); iii] Sintesi, caratterizzazione e attività catalitica di nuovi complessi dinucleari di Ir(III) con leganti di-NHC (Capitolo 4); iv] Reattività e proprietà coordinanti di leganti mono- e dicarbenici derivanti da unità carbeniche non-classiche (Capitolo 5). i] Sintesi e caratterizzazione di una serie di complessi mononucleari di Ir(III) aventi un legante di-NHC nella sfera di coordinazione. Una serie di nuovi complessi mononucleari di iridio(III), aventi un legante di-NHC coordinato è stata sintetizzata mediante reazione di transmetallazione del legante di-NHC dai corrispondenti complessi di argento(I) pre-formati, isolati e caratterizzati. Nei complessi di Ir(III) ottenuti, il legante di-NHC è coordinato al centro metallico in modo chelato; ciò è stato confermato da tecniche di caratterizzazione in soluzione e, per alcuni complessi, dalla risoluzione ai raggi X della struttura. Il protocollo sintetico ottimizzato è stato esteso a leganti di-NHC caratterizzati da diversi sostituenti agli atomi di azoto e da gruppi alchilici a ponte tra le unità carbeniche di diversa lunghezza. E’ stato valutato inoltre l’effetto dei sostituenti sulla densità elettronica presente sul metallo e sul carbonio carbenico. ii] Reazione di ossidazione di acqua catalizzata dai complessi mononucleari di-NHC di Ir(III) sintetizzati nell’ambito di questo progetto di Dottorato Alcuni dei complessi mononucleari di Ir(III) sintetizzati sono stato impiegati con successo come catalizzatori nella reazione di ossidazione di acqua in presenza di Ce(IV) (come (NH4)2[Ce(NO3)6], abbreviato con CAN) come ossidante sacrificale. Uno dei complessi più attivi (complesso 2) è stato testato anche in presenza di NaIO4, esibendo un’attività catalitica comparabile con quella riportata in letteratura per complessi Ir(III)-NHC. L’evoluzione del catalizzatore durante la catalisi è stata valutata determinando i gas prodotti utilizzando un GC-MS ed è stata osservata la formazione di una piccola quantità di CO2, il cui sviluppo è concomitante all’evoluzione di O2. La quantità di CO2 osservata deriva probabilmente dalla degradazione ossidativa dei leganti nella sfera di coordinazione del complesso. Il complesso 2 è stato inoltre utilizzato in un processo foto-indotto, accoppiato a un fotosensibilizzatore ([Ru(bpy)3]2+) ed a un accettore sacrificale di elettroni (S2O82-), mostrando una buona attività catalitica. Il comportamento del complesso 2 (in termini ad esempio di curva di evoluzione dell’ossigeno, tempo di vita del catalizzatore, resa quantica,…) è inoltre diverso da quanto osservato utilizzando IrCl3 nelle stesse condizioni sperimentali. E’ ben noto che IrCl3 è un precursore di IrOx nanoparticellare, perciò la differenza osservata può essere considerata una prova circa la natura molecolare del catalizzatore. Ulteriori investigazioni hanno permesso di identificare, attraverso misure EPR, la formazione di specie di Ir(IV), che è un intermedio probabile del ciclo catalitico; l’insieme di questi dati sembra confermare la natura molecolare del catalizzatore utilizzato. iii] Sintesi, caratterizzazione e attività catalitica di nuovi complessi dinucleari di Ir(III) con leganti di-NHC Utilizzando precursori dei leganti con gruppi lunghi e flessibili a ponte tra le unità carbeniche o aventi sostituenti con una funzionalità donatrice, sono stati sintetizzati nuovi complessi dinucleari di-NHC di iridio(III). Tali complessi sono stati completamente caratterizzati e, nel caso del complesso 15, è stata inoltre risolta la struttura ai raggi X. Questi complessi sono stati impiegati con successo come catalizzatori nella reazione di transfer hydrogenation di chetoni: è stato eseguito uno screening di substrati e i complessi, soprattutto 16, hanno mostrato una buona attività catalitica. iv] Reattività e proprietà coordinanti di leganti mono- e di-NHC derivanti da unità carbeniche non-classiche Nell’ambito di una collaborazione con il gruppo del Prof. C. J. (Kees) Elsevier (Università di Amsterdam), è stata valutata la possibilità di ottenere complessi di Ir(III) con leganti NHC saturi a sei membri. Sfortunatamente, i risultati ottenuti non sono stati soddisfacenti, probabilmente a causa della instabilità intrinseca dei precursori del leganti e/o dei corrispondenti carbeni liberi. Invece, risultati migliori sono stati ottenuti nella sintesi e nello studio della reattività di leganti misti NHC-MIC, infatti sono stati sintetizzati i corrispondenti complessi di argento(I) ed è stata eseguita una preliminare ottimizzazione delle condizioni di reazione per la transmetallazione Ag(I)/Ir(III) del legante; in questo modo è stato ottenuto un nuovo complesso di Ir(III) avente un legante NHC-MIC nella sfera di coordinazione.

The chapter one introduces the reported examples of rare earth metal (RE) complexes with different oxidation states. It also reviews the synthesis and reactivity study of N-heterocyclic carbene (NHC) supported transition metal and RE metal complexes. Chapter two focusses on the synthesis and characterisation of a series of tetraaryloxide Ce and Pr complexes. With the reaction of bulky tetraphenol proligand H4LR(R = P, PT, M) with four equivalents of KN"(N" = N(SiMe3)2), a dimerised complex of [K4LP]2(thf)11 was synthesised and characterised. The salt metathesis reactions of this complex with RECl3(thf)2 afford bimetallic aryloxide complexes of K2L2RE2(thf)11 (RE = Ce, Pr), which display divergent structures under different conditions. Reactions of the CeIII complex of K2L2Ce2(thf)11 with a variety of oxidants(I2, CuCl2 and O2, etc.) lead to the oxidation of CeIII to CeIV, affording purple ceric dimer of L2Ce2. The reaction of the PrIII complexes with I2 under 60 °C affords a mixture from which PrIII iodide (LPr2I2) has been isolated and characterised. This chapter also discusses the reactivity of the bimetallic aryloxide complexes towards different substrates, such as MeLi, KC8 and KBn (Bn = benzyl). Bimetallic complexes of L(REX)2(py)8 (RE = Ce, Pr; X = Cl, BH4) are synthesised and characterised. The preliminary study on the copolymerization of cyclohexene oxide (CHO) and CO2 is conducted for CeIII and PrIII complexes. Chapter three details the work on two different types of NHC ligand. The first ligand is the β-ketoimidazolinium salts H2LBr {L = RC(O)CH2{CH[NCH2CH2NMes], R = tBu, naphth} which reacts with MHBEt3 (M = Na, K) to form carbene-borane adducts RC(O)CH2{C(BEt3[NCH2CH2NMes]}. This type of reactivity differs from the previous work on imidazole derivatives. The possible mechanism of these reactions is provided and discussed. The other ligand is p-aryloxy-tethered imidazolinium salt H2LX (L = N-3,5-di-tert-butyl-4-hydrooxyphenyl-N’-mesityl-imidazolinium, X = Cl, Br, PF6 ), which have been synthesised and characterised. The reactions of these salts with MN"(M = Na, K) enabled the characterisation of polymerised complexes of [NaL]n and [KL(thf)2]n. The yttrium complex YL3 is synthesised and its reactivity towards small molecules such as boranes, CO2 and CS2 is discussed. Chapter four presents the primary results on the study of macrocyclic NHC based cyclophane ligand H6LPF6 (L = calix[4]imidazolylidene[2]pyrazolato). Investigations on the reactivity of the ligand towards different bases (NaN", KN", KBn etc.) are examined and subsequent metathesis reactions with RE complexes are explored. Chapter five concludes the work presented in this thesis. Chapter six contains all experimental and characterisation details.

Le glioblastome est la tumeur cérébrale la plus agressive avec un pronostic fatal, principalement à cause des cellules souches cancéreuses. Les médicaments à base de platine, utilisés pour traiter d’autres types de cancers, sont limités par l’apparition d’effets secondaires et le développement de résistances.Les complexes de platine à base de carbène N-hétérocyclique (NHC-Pt) ont été récemment identifiés comme des options thérapeutiques potentielles pour le traitement du glioblastome. Leur efficacité a été démontrée in vitro et in vivo pour éradiquer les cellules souches de glioblastome en ciblant les mitochondries.Dans cette contribution, de nouveaux complexes NHC-Pt ont été synthétisés pour éradiquer à la fois les cellules différenciées et souches de glioblastome. La nanoencapsulation des meilleurs composés a été réalisée pour faire face à leur faible solubilité dans l’eau sans perdre l’activité cytotoxique. Enfin, ces nanovecteurs ont été intégrés dans des hydrogels injectables pour permettre une libération localisée et contrôlée des complexes NHC-Pt
Glioblastoma is the most aggressive brain tumor with a fatal prognosis mainly due to cancer stem cells. Platinum-based drugs, used to treat other types of cancer, are limited by the emergence of side effects and the development of resistance.N-heterocyclic carbene platinum (NHC-Pt) complexes have been recently identified as potential therapeutic options for glioblastoma treatment. It has been demonstrated in vitro and in vivo efficacy in eradicating glioblastoma stem cells by targeting mitochondria.In this work, novel NHC-Pt complexes were synthetized to eradicate both glioblastoma differentiated and stem cells. Nanoencapsulation of the best compounds was performed to address poor water solubility without losing the cytotoxic activity. Finally, these nanovectors were integrated into injectable hydrogels to allow a localized and controlled release of the NHC-Pt complexes

The goal of this PhD was to elaborate supported Ru-NHC catalytic materials based on hybrid organic-inorganic materials having imidazolium units perfectly distributed within a silica matrix. Passivation of these imidazolium materials followed by formation of NHC-carbene and reaction with [RuCl2(p-cymene)]2 provided these well-defined surface sites of general structures RuCl2(NHC)(L), where L was para-cymene (p-cymene) or THF depending on the reaction conditions, which could be further replaced by PMe3. These systems were then tested in the hydrogenation of CO2 in presence of amine to give formamides. The mono-NHC systems were highly active only in the presence of PMe3 ligands, but suffered from Ru leaching, evidencing the low stability of the NHC-Ru bond under the reaction conditions. On the other hand, dinuclear bis-NHC Ru systems were also developed, and they displayed much improved activity and stability in the hydrogenation of CO2 in the presence of PMe3 compared to the mono-NHC systems. This allowed the use of much higher reaction temperatures (200 °C) and provided heterogeneous catalysts with performances close to those obtained with the best homogeneous catalysts, Cl2Ru(dppe)2.

Les carbènes N-hétérocycliques (NHC) sont connus pour être de bons ligands des métaux de transition (TM). Dans ce manuscrit, le premier chapitre est consacré une présentation non exhaustive des différentes approches qui ont été utilisées dans la littérature pour le design de NHCs chiraux efficaces en catalyse enantiosélective. Au début du deuxième chapitre, le nouveau concept est présenté. Celui-ci repose sur la formation d’un axe de chiralité qui est créé lors de la coordination du ligand NHC à un métal de transition. Ce chapitre est consacré à la synthèse de complexes possédant une symétrie C1. Différents sels d’imidazolium, précurseurs des NHCs, ont été synthétisés et utilisé pour former des complexes palladium. Ils ont été sous forme énantiopure par HPLC chirale à l’échelle préparative. Ces complexes ont fait l’objet d’études concernant leurs propriétés chiroptiques et leurs barrières de rotation avant d’être testé en catalyse. Le concept a été ensuite étendu pour la synthèse de complexes d’or et de cuivre. Ces derniers se sont avérés être intéressants car non seulement ils ont permis d’obtenir de bons excès énantiomériques en catalyse mais leurs utilisations comme agent de transfert de ligands NHC a permis de proposer un mécanisme pour le procédé de transmétallation. Le troisième chapitre fait état des travaux qui ont été réalisés sur la préparation de complexes chiraux NHC-TM possédant une symétrie C2. Différents sels d’imidazolium symétriques ont été synthétisés et utilisés pour former des complexes de palladium. Les versions homochirales de ces complexes se sont avérées être d’excellents catalyseurs chiraux pour la réaction l’α-arylation d’amides (jusqu’à 98% ee)
N-heterocyclic carbenes (NHC) are recognized to be excellent ligands towards transition metals ™. In this manuscript, the first chapter is dedicated to a non-exhaustive presentation of the various approaches of the literature which have been used to design chiral NHCs efficient in enantioselective catalysis. As a prelude of the second chapter, the new concept lies on the formation of an axis of chirality during the coordination between the NHC ligand and the transition metal. This chapter is dedicated to the synthesis of complexes with a C1 symmetry. Various imidazolium salts, have been synthesized and then used to generate palladium complexes. These complexes have been obtained in a enantiopurically form thanks to a chiral HLPC resolution at a preparative scale. These homochiral complexes were firstly subjected to studies aiming the investigation of their chiroptic properties and the determination of their rotation barriers values. The concept was then successfully extended to the synthesis of gold- and copper-based complexes. Homochiral copper-NHC complexes were found of particular importance since their applications in catalysis allowed to reach good enantioinductions and as NHC transfer reagents brought some experimental proofs on the transmetalation process. The third chapter disclosed the works that have been done on the preparation of heterochiral NHC-TM complexes possessing a C2 symmetry. Various symmetric imidazolium salts have been synthesized and then used to form the corresponding palladium-based complexes. Homochiral complexes were found displaying good activities for α-arylation of amides and excellent enantioselectivities (up to 98% ee)

Afin de développer des méthodes alternatives à l'activation de systèmes Pi en catalyse homogène par des métaux nobles coûteux et toxiques, nous nous sommes focalisés sur des complexes métalliques et plus particulièrement ceux de la colonne du group XIII. Cette thèse approche une contribution à ce champ d'études, et nous nous sommes particulièrement concentrés sur la chimie de gallium.Trois principaux aspects ont été étudiés dans ce manuscrit: la réactivité des halogénures de gallium(III), des complexes bien définis de gallium (III) portant carbènes N- hétérocycliques (NHCs), et leur activation de systèmes en catalyse.La thèse est divisée en trois chapitres. Le premier chapitre donne un aperçu des travaux effectués dans le domaine de la synthèse organique faisant intervenir des composés de gallium (III) , en se concentrant sur ​​leur utilisation en tant qu’ acides de Lewis et .Dans le deuxième chapitre, nous avons tenté d'exploiter le potentiel catalytique de GaCl3 dans une nouvelle réaction de cycloisomérisation/Friedel-Crafts en tandem. Une section dédiée à l'étude sur l’hydratation d’alcyne catalysée par GaCl3 est également fournie.Le troisième chapitre commence par une description de la synthèse d'une série de complexes de gallium (III) portant diverses NHCs comme ligands pour surmonter les limites des halogénures de gallium(III) en catalyse. Ensuite, des études de méthodologie sur le processus de tandem impliquant arenynes-1,6 avec les gallium(III) complexes neutres et cationiques ont été décrits. Une évaluation cinétique pour des catalyseurs, des divers substrats et l'influence de contreanions sont discutés. En outre, les efforts dans la version asymétrique de cette tandem transformation et des autres cyclisations sont également présentés.Le dernier chapitre reprend les résultats les plus importants obtenus dans la thèse. Et les orientations futures de la recherche sur l'utilisation des complexes NHC- gallium (III) sont discutées
Recently, in order to develop alternative activation methods for Pi-systems in homogeneous catalysis instead of employing expensive and toxic noble metal catalysts, first row transition metals and main group metal complexes have attracted great attention. This thesis is a contribution to it, and we focus on gallium chemistry. There are three main aspects dominating this thesis: gallium(III) halides, well-defined gallium(III) complexes bearing N-heterocyclic carbenes (NHCs), and -systems activation in catalysis.The thesis is divided into three chapters. Chapter I provides an overview of the field of organic synthesis involving gallium(III) compounds, focusing on their use as - or -Lewis acids.In Chapter II, we expose our attempts to exploit the catalytic potential of gallium(III) chloride in a novel tandem cycloisomerization/Friedel-Crafts reaction. A section dedicated to the study on GaCl3-catalyzed alkyne hydration is also provided.Chapter III begins with a description of the synthesis of a series of gallium(III) complexes bearing various NHCs as ligands in order to overcome the limitations of gallium(III) halides in catalysis. Next, methodology studies on the tandem process involving 1,6-arenynes with the neutral and cationic gallium(III) complexes are described. The evaluation of scission kinetics for catalysts, substrates variation and influence of counteranions are discussed. In addition, efforts towards the asymmetric version of this tandem transformation and some other cyclizations are also presented.The concluding chapter reiterates the most important results obtained in the body chapters of the thesis. To conclude, the future directions for the research on the use of the NHC-gallium(III) complexes are discussed

Au début de ces travaux, peu d’études avaient été faites sur la complexation des carbènes N-hétérocycliques avec des métaux oxophiles, électropositifs et à hauts degrés d’oxydation tel que les métaux du groupe 13. L’optimisation de voies de synthèse a permis d’étendre le nombre de complexes de types NHC-MIII (M = aluminium, gallium et indium), ainsi qu’à des complexes cationiques. L’association de ces précurseurs avec des NHCs plus encombrés a permis l’observation de réactivités sans précédent (complexes anormaux, paires de Lewis frustrées, dicarbènes N-hétérocycliques). Dans un second temps, la réactivité inhabituelle des ligands NHCs a permis l’isolation d’analogue au réactif de Tebbe, très actifs en méthylénation de dérivés carbonyles
At the beginning of this work, few studies had been performed on the complexation of N-heterocyclic carbenes with oxophilic metals, in high oxidation states such as group 13 metals. The synthetic routes optimization has extended the number of complexes-type NHC-MIII (M = aluminum, gallium and indium), and the corresponding cationic complexes. The combination of these precursors with sterically congested NHCs allowed the observation of unprecedented reactivities (abnormal complexes, Frustrated Lewis Pairs, N-heterocyclic dicarbenes). In a second step, the unusual reactivity of NHC ligands has allowed the isolation of analogues of the Tebbe’s reagent, formed to be very active in the methylenation of carbonyl compounds

Earth-abundant first-row transition metals have seen a renaissance in chemistry in recent years due to their relatively low toxicity and cost in comparison to precious metals. Furthermore open-shell transition metal complexes exhibit useful one-electron redox processes which contrasts to their heavier d block anologues. This thesis aims to synthesize and analyse the structure and reactivity of low-coordiante first-row transition metal complexes of from groups 7-9 with an aim to utilize these species in catalysis. The divalent compound [Co{N(SiMe3)2}2] reacts with the primary phosphines PhPH2 in the presence of an NHC ligand (IMe4) to yield the phosphinidene bridged dimer [(IMe4)2Co(µ-PMes)]2. The complex has interesting magnetic properties due to strong antiferromagnetic coupling between the two cobalt(II) centres. Increasing the steric bulk of the NHC yielded carbene-phosphinidene adducts (NHC·PAr). This transformation was shown to be catalytic. The structure and reactivity of complexes of the type [(NHC)xMn{(N(SiMe3)2}2] were investigated. The complexes exhibit similar structural properties to their iron and cobalt analogues; however their reactivity has been shown to differ. The addition of primary phosphines to complexes of the type [(NHC)xMn{N(SiMe3)2}2] yielded a range of manganese phosphide complexes. [Mn{N(SiMe3)2}2] also reacts with imidazolium salts at elevated temperatures to yield heteroleptic manganese NHC complexes. The reaction of [Mn{N(SiMe3)2}2] with IPr·HCl afforded the abnormal carbene complex [(aIPr)Mn{N(SiMe3)2}µ-Cl]2. A new monoanionic bidentate ligand is reported which has shown to be a useful ligand system to stabilize three-coordiante iron(II) complex. The reaction of [(L)Fe(Br)] with mesitylmagnesium Grignard or n-butyllithium yield the iron hydrocarbyls [(L)Fe(Mes)] and [(L)Fe(nBu)] with the latter being stable to β-hydrogen elimination. Finally [(L)Fe(nBu)] has been utilized as a pre-catalyst in the hydrophosphination of internal alkynes, showing selectivity for the E-isomeric vinylphosphine.

L’objectif de cette thèse était d’élaborer des matériaux antibactériens en utilisant la chimie de coordination. Pour ce faire, ce travail a été mené selon trois axes de recherche distincts. Dans une première partie, nous avons synthétisé des polymères de coordination (CP) par auto-assemblage de ligands dithioéthers avec des sels d’argent(I). Cette approche se démarque de travaux précédents par l’utilisation d’une combinaison acide de Lewis faible/ligand donneur mou. Outre la caractérisation structurale de ces CPs, ce travail présente une étude approfondie de leur activitié antibactérienne et de leur cytotoxicité. Dans une seconde partie, la synthèse de complexes carbéniques portant un groupement pyrrole électroactif et leur électropolymérisation pour former des films de métallopolymère est décrite. Cette approche par voie électrochimique pour immobiliser des complexes carbéniques sur des substrats est tout à fait originale par rapport aux travaux de la littérature. A la fois la nature du métal (Ag(I), Au(I), Rh(I), Ru(II), Cu(I)) et leur teneur dans les films mènent à des activités antibactériennes très différentes. Ces films ont également montré une réponse métal-dépendante des bactéries. Finalement, nous avons utilisé de façon assez atypique la méthode d’assemblage couche par couche (LbL) pour fonctionnaliser des surfaces de titane par des CPs.Les résultats présentés sont donc le fruit d’un travail pluridisciplinaire alliant la synthèse organique, la chimie de coordination, l’électrochimie, la chimie de surface et la (micro)biologie
The aim of this thesis was to develop antibacterial materials using coordination chemistry. To this end, the work was carried out along three distinct lines of research. In the first part, we synthesized coordination polymers (CPs) by self-assembly of dithioether ligands with silver(I) salts. This approach differs from previous work by using a weak Lewis acid/soft donor ligand combination. In addition to the structural characterization of these CPs, this work presents an in-depth study of their antibacterial activity and cytotoxicity. In a second part, the synthesis of carbene complexes bearing an electroactive pyrrole group and their electropolymerization to form metallopolymer films is described. This electrochemical approach to immobilize carbene complexes on substrates is highly original compared with the literature. Both the nature of the metal (Ag(I), Au(I), Rh(I), Ru(II), Cu(I)) and their content in the films result in very different antibacterial activities. These films also showed a metal-dependent response to the bacteria. Finally, in a rather atypical way, we used the layer-by-layer (LbL) assembly method to functionalize titanium surfaces with CPs.The results presented here are therefore the fruit of multidisciplinary work combining organic synthesis, coordination chemistry, electrochemistry, surface chemistry and (micro)biology

Le premier chapitre de ce manuscrit est consacré à l’étude des différents designs de NHCs chiraux décrits dans la littérature et leurs applications en tant que ligand dans les transformations énantiosélectives catalysées par l’or. Un nouveau concept de complexes atroipsomériques métal de transition-NHC a été conçu et développé dans notre groupe. Son application pour préparer des complexes de métaux de transition chiraux portant un ligand NHC de symétrie C1 contenant un NHC saturé a été étudiée au cours de mes travaux de doctorat et sera présentée dans le deuxième chapitre. Divers complexes chiraux ont été obtenus, séparés par HPLC chirale à l’échelle préparative et leurs stabilités configurationnelles ont été étudiées en profondeur. Le complexe contenant de l’or(I) a été testé pour la cycloisomérisation d’1,6-énynes, donnant une énantiosélectivité prometteuse (70% ee). Dans le troisième chapitre de ce manuscrit, le concept de complexes atroipsomériques métal de transition-NHC a été étendu à des ligands NHCs de symétrie C2 et appliqué des transformations asymétriques catalysées par de l’or(I). Les 1,6-énynes possédant un lien malonate de diisopropyle se sont avérés être d’excellents substrats pour des réactions de cycloisomérisation et les produits d’alcoxycyclisation qui en ont résultées ont été isolés avec d’excellentes énantiopuretés (7 exemples avec des rendements de 51 à 92% et des excès énantiomériques compris entre 56 et 99%). La cycloisomérisation lorsqu’elle est réalisée sans nucléophile externe a également conduit à d’excellents résultats (6 exemples avec des rendements allant de 72 à 99%, et des excès énantiomériques dans la gamme 86-93% ee)
The first chapter of this manuscript is dedicated to survey the design of chiral NHC and their applications as ligand in gold-catalyzed enantioselective transformations. This presentation clearly showed the importance of new ligand designs, because only poor enantioselectivities have been reached up to date. A new concept of atroipsomeric transition metal-NHC complexes has been devised and developed in our group. Its application to prepare chiral transition metal complexes bearing C1-symmetric NHC ligand containing a satured backbone was investigated during my Ph.D. work and will be presented in the second chapter. Various chiral complexes were obtained, separated by chiral HPLC at preparative scale and their configurational stabilities were investigated in depth. The gold (I) containing complex was tried in the 1,6-enyne cycloisomerization, giving a promissing enantioselectivity (70% ee). In the third chapter of this manuscript, the concept of atroipsomeric transition metal-NHC complexes was extended to C2-symmetric NHC ligands and applied to the asymmetric Au(I)-catalyzed transformations. Diisopropyl malonate-tethered 1,6-enynes were identified as excellent substrates for cycloisomerization reactions and resulting alkoxycyclization products were isolated with excellent enantiopurities (7 examples with 51-92% yield, 56-99% ee). The cyclization without external nucleophiles led also to excellent results a (6 examples with 72-99% yield, 86-93% ee)

Platinum(II) complexes [(NHC)Pt(L)] with various β-diketonate based auxiliary ligands (L: 3-meacac = 3-methylacetylacetonato, dpm = dipivaloylmethanato, dbm = dibenzoylmethanato, mesacac = dimesitoylmethanato, duratron = bis(2,3,5,6-tetramethylbenzoyl)methanato) and a C^C* cyclometalated N-heterocyclic carbene ligand (NHC: dpbic = 1,3-iphenylbenzo[d]imidazol-2-ylidene, dpnac = 1,3-diphenylnaphtho[2,3-d]imidazol-2-ylidene or bnbic = 1-phenyl-3-benzylbenzo[d]imidazol-2-ylidene) were found to show different aggregation and photophysical properties depending on the auxiliary ligand. Eight complexes were prepared from a silver(I)–NHC intermediate by transmetalation, cyclometalation and subsequent treatment with potassium-tert-butanolate and β-diketone. They were fully characterized by standard techniques including ¹⁹⁵Pt NMR. Five complexes were additionally characterized by 2D NMR spectroscopy (COSY, HSQC, HMBC and NOESY). Solid-state structures of five complexes could be obtained and show the tendency of the square-planar compounds to form pairs with different Pt–Pt distances depending on the bulkiness of the substituents at the auxiliary ligand. The result of the photophysical measurements in amorphous PMMA films reveals quantum yields of up to 85% with an emission maximum in the blue region and comparatively short decay lifetimes (3.6 µs). Density functional theory (DFT/TD-DFT) calculations were performed to elucidate the emission process and revealed a predominant ³ILCT/³MLCT character. Organic light-emitting devices (OLEDs) comprising one of the complexes achieved 12.6% EQE, 11.9 lm W⁻¹ luminous efficacy and 25.2 cd A⁻¹ current efficiency with a blue emission maximum at 300 cd m⁻². The influence of an additional hole-transporter in the emissive layer was investigated and found to improve the device lifetime by a factor of seven.

Les complexes métalliques des carbènes N-hétérocycliques (NHC) présentent un grand potentiel comme anticancéreux. En particulier, des études in vitro ont confirmés une cytotoxicité supérieure au cisplatine. Dans ce travail, nous avons introduit de la diversité moléculaire à de nouveaux complexes NHC-Pt par coordination de différents ligands NHC. Une deuxième stratégie, la post-fonctionnalisation de complexes de Pt a été étudié par : a) formation d’oxime, notamment avec une urée ciblant le PSMA, b) échange de ligand avec des polyamines hydrosolubles (PEI) ou des pnictogènes (phosphines, arsines, stibines), c) échange d’halogène avec des isotopes de l’iode. Les propriétés cytotoxiques de ces composés ont été évaluées in vitro. In vivo (souris), un complexe PEI-Pt montre une inhibition tumorale similaire à l’oxaliplatine. Néanmoins, aucun effet secondaire n’a été détecté contrairement à l’oxaliplatine (hématomes). Ces résultats ouvrent de nouvelles perspectives dans le domaine des anticancéreux sur la base de platine
Metal N-Heterocyclic Carbene (NHC) complexes are of great potential for cancer therapy. In particular, in vitro studies confirmed their significantly higher cytotoxicity than cisplatin. In this work, we introduced molecular diversity on new NHC-Pt complexes by coordination of various NHC precursors to platinum. As a second strategy, post-synthetic functionalization of Pt complexes has been fully investigated by: a) oxime formation, e.g. with a PSMA targeting urea derivative, b) ligand exchange reaction with hydrosoluble polyamines (PEI) and pnictogen-based ligands (phosphines, arsines, stibines), c) halogen exchange with iodide isotopesCytotoxic properties of these new compounds were evaluated in vitro. Best candidate was selected for in vivo evaluation on mice model showing for PEI-Pt similar tumour inhibition as oxaliplatin. Besides, no “visual” side effects were detected in contrast to oxaliplatin (hematomas). These outstanding results opened up new perspectives in the field of platinum-based drugs

This thesis is concerned with the synthesis of two di-N-heterocyclic carbene ligands, and their reactivity towards nickel and palladium precursors in order to synthesise new organometallic pre-catalysts for a number of important reactions. The catalytic properties of a new rhodium C₆₀ compound are also investigated, with relevance to the evaluation of C₆₀ as a hydrogen storage medium. Chapter 1 reviews the preparation and chemistry of N-heterocyclic carbenes, emphasising their organometallic reactivity and role as ancillary ligands in homogeneous transition metal catalysis. An overview of relevant nickel and palladium catalysis is also presented, including olefin polymerisation, olefm / CO copolymerisation and Heck coupling reactions. Chapter 2 describes the synthesis and characterisation of the dicarbene ligands ^tBuCC^meth and ^tBuCC^eth and their reactions with various nickel precursors in attempts to prepare chelating dicarbene nickel cis-dihalide complexes. The synthesis, characterisation and chemical reactivity of the cations [Ni(^tBuCC^meth)₂]²⁺, [(^tBuCC^meth)NiCl(PMe₃)] ⁺ and [(^tBuCC^eth)NiCl(PMe₃)]⁺ is detailed, and their X-ray structures are compared. The unsuccessful preparation of [Ni(^tBuCC^eth)₂] ²⁺ and the relative stability of the monocations with respect to dicarbene substitution is discussed and attributed to steric factors. Chapter 3 describes the synthesis, characterisation, reactivity and catalytic studies of simple nickel and palladium cis-dimethyl complexes of the chelating dicarbene ligands. Variable temperature ¹H NMR spectroscopy showed contrasting rates of thermal hydrocarbon elimination from Ni(^tBuCC^meth)Me₂ and Ni(^tBuCC^eth)Me₂, which has previously been observed for chelating bis-phosphine analogues with various P,P' linkages (CH₂)_n . These observations further corroborate the analogy between dicarbene and 6/s-phosphine ligands. It was demonstrated that the compounds Pd(^tBuCC^meth)Me₂and Pd(^tBuCC^eth)Me₂ are effective pre-catalysts for the Heck coupling of 4-bromoanisole and n-butyl acrylate. In addition cations of the type [(^tBuCC^meth/eth)PdMe(L)]⁺ (L = pyridine, THF) which are relevant to olefin / CO copolymerisation were prepared. The X-ray structures of M(^tBuCC^eth)Me2 (M = Ni, Pd) are discussed as well as the synthesis and structural characterisation of [(|Li-tBu CC meth){Ni(PMe₃)Me₂}₂]. Chapter 4 presents a brief introduction to some relevant C₆₀ chemistry and to the concept of hydrogen storage. The synthesis and characterisation of a new rhodium Ceo compound is described. The compound catalysed the hydrogenation and hydroformylation of simple alkenes as well as the hydrogenation of C₆₀ to C₆₀H₃₆ . The recovery of hydrogen gas from C₆₀H₃₆ was investigated in order to evaluate C₆₀ as a hydrogen storage medium. Chapter 5 outlines the experimental details for the synthesis, characterisation, reactions and catalytic studies of the new compounds described in the preceding three chapters. Chapter 6 presents the characterising data for the new compounds described in chapters 2 and 3. Appendices contain details of the crystallographic data for the eight structurally characterised compounds described in chapters 2 and 3.

This thesis is comprised of two parts. The first part describes the synthesis of cyclopentadienyltungsten complexes containing a pendant alkyne group (I), and the subsequent photo-induced intramolecular coordination of the alkyne, forming complexes such as II. Compounds containing intramolecularly coordinated alkynes are rare, and this is the first example using cyclopentadiene as the core ligand. The second part describes the synthesis and structural characterisation of a number of novel metal complexes containing N-heterocyclic carbene ligands, some containing particular functionality for taylored applications. New methods were used to form complexes of rhodium, iridium, silver and gold (eg. III, IV). Structural and spectroscopic properties of the complexes were correlated with electronic characteristics of the ancillary ligands. A number of rhodium and iridium complexes (eg. IV) derived from imidazolium-linked cyclophanes were synthesised and structurally characterised. Complexes of N-heterocyclic carbenes with pendant ionic groups were synthesised, and a preliminary examination of their catalytic activity in water was performed. N-Heterocyclic carbenes complexes containing an electron withdrawing nitro group were synthesised and the effect of the nitro group on metal-ligand bonding was examined.