Artykuły w czasopismach: „NHC Ligand”

1

Rais, Eduard, Ulrich Flörke i René Wilhelm. "Crystal structures of diiodidobis[(1S,5S)-4-mesityl-1,2,8,8-tetramethyl-2,4-diazabicyclo[3.2.1]octan-3-ylidene-κC3]palladium(IV) and dichlorido[(1S,5S)-4-mesityl-1,2,8,8-tetramethyl-2,4-diazabicyclo[3.2.1]octan-3-ylidene-κC3](triphenylphosphane-κP)palladium(IV)". Acta Crystallographica Section E Crystallographic Communications 71, nr 8 (11.07.2015): 919–22. http://dx.doi.org/10.1107/s2056989015013055.

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The molecular structures of the chiral title compounds, [Pd(C19H28N2)2I2], (I), and [Pd(C19H28N2)Cl2(C18H15P)], (II), show a distorted square-planar coordination around the PdIIatoms with two halogenide (Hal) ligands each and two N-heterocyclic carbene (NHC) ligands in (I) or one NHC and one triphenylphosphane ligand in (II). The deviations of the PdIIatoms from theL2Hal2best plane (L= NHC or triphenylphosphane ligand) are 0.206 (1) Å for (I) and 0.052 (1) Å for (II). The crystal packings exhibit intermolecular C—H...Hal hydrogen bonds.

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2

Diesel, Johannes, i Nicolai Cramer. "Modular Chiral N-Heterocyclic Carbene Ligands for the Nickel-Catalyzed Enantioselective C–H Functionalization of Heterocycles". CHIMIA International Journal for Chemistry 74, nr 4 (29.04.2020): 278–84. http://dx.doi.org/10.2533/chimia.2020.278.

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N-Heterocyclic carbenes (NHCs) are the ligands of choice in a large variety of transformations entailing different transition metals. However, the number and variety of chiral NHCs suitable as stereo-controlling ligands in asymmetric catalysis remains limited. Herein we highlight the introduction of a modular NHC ligand family, consisting of a chiral version of the widely used IPr ligand. These chiral NHC ligands were applied in the nickel-catalyzed enantioselective C–H functionalization of N-heterocycles. Nickel-NHC catalysis unlocked the stereoselective C–H annulation of 2- and 4-pyridones, delivering fused bicyclic compounds found in many biologically active compounds. Applying a bulky, yet flexible ligand scaffold enabled the highly enantioselective C–H functionalization of pyridones under mild conditions. The introduction of a bulky chiral SIPr analogue enabled the nickel-catalyzed enantioselective C–H functionalization of indoles, yielding valuable tetrahydropyridoindoles. Additionally, pyrrolopyridines, pyrrolopyrimidines and pyrroles were efficiently functionalized, delivering chiral annulated azoles.

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3

Iannuzzi, Theresa E., Yafei Gao, Tessa M. Baker, Liang Deng i Michael L. Neidig. "Magnetic circular dichroism and density functional theory studies of electronic structure and bonding in cobalt(ii)–N-heterocyclic carbene complexes". Dalton Transactions 46, nr 39 (2017): 13290–99. http://dx.doi.org/10.1039/c7dt01748k.

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The combination of simple cobalt salts and N-heterocyclic carbene (NHC) ligands has been highly effective in C–H functionalization, hydroarylation and cross-coupling catalysis, though displaying a strong dependence on the identity of the NHC ligand.

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4

Dröge, Thomas, i Frank Glorius. "NHC - Ligand der Ideen". Nachrichten aus der Chemie 58, nr 2 (luty 2010): 112–17. http://dx.doi.org/10.1002/nadc.201069673.

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5

Suresh, Lakshmi, Ralte Lalrempuia, Jonas B. Ekeli, Francis Gillis-D’Hamers, Karl W. Törnroos, Vidar R. Jensen i Erwan Le Roux. "Unsaturated and Benzannulated N-Heterocyclic Carbene Complexes of Titanium and Hafnium: Impact on Catalysts Structure and Performance in Copolymerization of Cyclohexene Oxide with CO2". Molecules 25, nr 19 (23.09.2020): 4364. http://dx.doi.org/10.3390/molecules25194364.

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Tridentate, bis-phenolate N-heterocyclic carbenes (NHCs) are among the ligands giving the most selective and active group 4-based catalysts for the copolymerization of cyclohexene oxide (CHO) with CO2. In particular, ligands based on imidazolidin-2-ylidene (saturated NHC) moieties have given catalysts which exclusively form polycarbonate in moderate-to-high yields even under low CO2 pressure and at low copolymerization temperatures. Here, to evaluate the influence of the NHC moiety on the molecular structure of the catalyst and its performance in copolymerization, we extend this chemistry by synthesizing and characterizing titanium complexes bearing tridentate bis-phenolate imidazol-2-ylidene (unsaturated NHC) and benzimidazol-2-ylidene (benzannulated NHC) ligands. The electronic properties of the ligands and the nature of their bonds to titanium are studied using density functional theory (DFT) and natural bond orbital (NBO) analysis. The metal–NHC bond distances and bond strengths are governed by ligand-to-metal σ- and π-donation, whereas back-donation directly from the metal to the NHC ligand seems to be less important. The NHC π-acceptor orbitals are still involved in bonding, as they interact with THF and isopropoxide oxygen lone-pair donor orbitals. The new complexes are, when combined with [PPN]Cl co-catalyst, selective in polycarbonate formation. The highest activity, albeit lower than that of the previously reported Ti catalysts based on saturated NHC, was obtained with the benzannulated NHC-Ti catalyst. Attempts to synthesize unsaturated and benzannulated NHC analogues based on Hf invariably led, as in earlier work with Zr, to a mixture of products that include zwitterionic and homoleptic complexes. However, the benzannulated NHC-Hf complexes were obtained as the major products, allowing for isolation. Although these complexes selectively form polycarbonate, their catalytic performance is inferior to that of analogues based on saturated NHC.

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6

Mattoussi, Hedi, Liang Du, Neda Arabzadeh Nosratabad i Zhicheng Jin. "(Keynote) N-Heterocyclic Carbene-coated Gold Nanoparticles and Luminescent Quantum Dots". ECS Meeting Abstracts MA2022-02, nr 20 (9.10.2022): 904. http://dx.doi.org/10.1149/ma2022-0220904mtgabs.

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N-heterocyclic carbenes (NHCs) have generated much interest for use as versatile metal-coordinating groups, since they were first synthesized by Arduengo and coworkers in 1991. NHC molecules can be considered as L-type ligands, because they share their non-bonding electron pairs with the σ-accepting orbital of transition metals, and this endows them with strong coordination interactions. NHC-appended molecules have recently been actively exploited as potentially effective ligands for the surface passivation of various colloidal nanomaterials. We investigate the coordination interactions between a few representative colloidal nanocrystals, including gold nanoparticles (AuNPs) and luminescent quantum dots (QDs), and a NHC-based polymer ligand. The latter presents multiple NHC groups and several short poly (ethylene glycol) (PEG) chains as solubilizing blocks. We find that our NHC-decorated ligands rapidly coordinate onto both sets of nanocrystals, which we attribute to their soft Lewis base nature. These ideally match the soft Lewis acid character of transition metal colloid surfaces, promoting strong coordination bonding through soft‐soft interaction. We combine NMR spectroscopy, fluorescence spectroscopy, high-resolution transmission electron microscopy supplemented with dynamic light scattering to characterize the nature of the binding interactions. Furthermore, the long-term stability of the NHC-stabilized nanocolloids have been tested after phase transfer to water, a highly challenging chemical venue for such groups, due to the moisture sensitive nature of NHC molecules. Data show that our NHC-polymer-stabilized AuNPs and QDs exhibit long-term colloidal stability in buffer media while preserving their optical and fluorescing properties, with no sign of degradation or aggregation build up for at least one year of storage. We will discuss the ligand design and synthesis, characterization of the polymer-stabilized nanocrystals under various conditions, with a particular focus on the beneficial effects of ligand multi-coordination interactions onto the nanocolloid surfaces.

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7

Mostafa, Mohamed A. B. "Review Study of Chiral N-Heterocyclic Carbene (NHC) Ligands in Stereoselective Metal-Catalyzed Reduction Reactions". Scientific Journal for Faculty of Science-Sirte University 2, nr 1 (17.04.2022): 116–25. http://dx.doi.org/10.37375/sjfssu.v2i1.210.

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Stereoselective metal-catalyzed reactions using N-heterocyclic carbene (NHC) ligands have shown significant recent advances, due to the ability of NHC ligands as strong σ-donor species to coordinate with a wide variety of transition metals. Therefore, the design of new ligands and the subsequent strategies for their synthesis enables new applications of their metal complexes in catalysis to be investigated. This study focuses on the applications of different classes of Ir-, Pd- , Au- and Rh-NHC ligand complexes as promising catalysts in the asymmetric hydrogenation, hydrosilylation and transfer hydrogenation reactions.

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8

Chan, Chung Ying, i Peter J. Barnard. "Rhenium complexes of bidentate, bis-bidentate and tridentate N-heterocyclic carbene ligands". Dalton Transactions 44, nr 44 (2015): 19126–40. http://dx.doi.org/10.1039/c5dt03295d.

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Rhenium(i) tricarbonyl complexes of a range of bidentate, bis-bidentate and tridentate NHC ligands have been prepared. These NHC ligands are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and the stability of two complexes were evaluated in ligand challenge experiments using the metal binding amino acids l-histidine or l-cysteine.

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9

Tacke, Matthias, Oyinlola Dada, Cillian O'Beirne, Xiangming Zhu i Helge Müller-Bunz. "The non-isomorphous crystal structures of NHC—Au—Cl and NHC—Au—Br (NHC is 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)". Acta Crystallographica Section C Structural Chemistry 72, nr 11 (5.10.2016): 857–60. http://dx.doi.org/10.1107/s2053229616015205.

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Gold monochloride and monobromide can be transformed into monomeric complexes by ligands such as CO, PPh3or Me2S, and such ligand-stabilized gold monochloride compounds have been investigated as catalysts, luminescent materials and anticancer drugs, especially when coordinated to a lipophilic benzyl-substituted N-heterocyclic carbene (NHC) ligand. The triclinic structures of NHC–Au–Cl {chlorido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)gold, [AuCl(C29H24N2)]} and NHC—Au—Br {bromido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)gold, [AuBr(C29H24N2)]}, determined by X-ray crystallography at 100 K, have one and four molecules, respectively, in their asymmetric units. The chloride compound shows an almost linear C—Au—Cl fragment [179.76 (8)°], with an Au—C distance of 1.976 (3) Å and an Au—Cl distance of 2.3013 (6) Å, while the bromide compound shows surprisingly large geometry deviations, from 1.969 (12) to 2.016 (10) Å for the Au—C distance and from 2.4279 (14) to 2.4796 (12) Å for the Au—Br distance, in the four independent molecules.

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10

Keita, Hamidou. "Supramolecular Immobilization of Adamantyl and Carboxylate Modified N-Heterocyclic Carbene Ligand on Cucurbituril Substrates". Molecules 27, nr 5 (3.03.2022): 1662. http://dx.doi.org/10.3390/molecules27051662.

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Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by 1H-NMR, 13C-NMR, FTIR, single crystal x-ray crystallography and elemental analysis. A proof-of-principle non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using 1H-NMR titration.

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11

Diaz-Rodriguez, Roberto M., Katherine N. Robertson i Alison Thompson. "Classifying donor strengths of dipyrrinato/aza-dipyrrinato ligands". Dalton Transactions 48, nr 22 (2019): 7546–50. http://dx.doi.org/10.1039/c9dt01148j.

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12

Mejuto, Carmen, Beatriz Royo, Gregorio Guisado-Barrios i Eduardo Peris. "Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities". Beilstein Journal of Organic Chemistry 11 (14.12.2015): 2584–90. http://dx.doi.org/10.3762/bjoc.11.278.

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The coordination versatility of a 1,3,5-triphenylbenzene-tris-mesoionic carbene ligand is illustrated by the preparation of complexes with three different metals: rhodium, iridium and nickel. The rhodium and iridium complexes contained the [MCl(COD)] fragments, while the nickel compound contained [NiCpCl]. The preparation of the tris-MIC (MIC = mesoionic carbene) complex with three [IrCl(CO)2] fragments, allowed the estimation of the Tolman electronic parameter (TEP) for the ligand, which was compared with the TEP value for a related 1,3,5-triphenylbenzene-tris-NHC ligand. The electronic properties of the tris-MIC ligand were studied by cyclic voltammetry measurements. In all cases, the tris-MIC ligand showed a stronger electron-donating character than the corresponding NHC-based ligands. The catalytic activity of the tri-rhodium complex was tested in the addition reaction of arylboronic acids to α,β-unsaturated ketones.

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13

Jahnke, Mareike C., Tania Pape i F. Ekkehardt Hahn. "Ligand Exchange at a Gold(I) Carbene Complex". Zeitschrift für Naturforschung B 68, nr 5-6 (1.06.2013): 467–73. http://dx.doi.org/10.5560/znb.2013-3076.

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Gold complex [AuCl(NHC)] (NHC=N,N0-dipropylbenzimidazolin-2-ylidene) 1 undergoes facile substitution reactions at the gold(I) center. Treatment of 1 with anionic phenylacetylide or thiophenolate led to the neutral gold complexes 2 and 3, respectively. The cationic gold complexes [Au(NHC)(pyridine)](BF4) [4]BF4 and [Au2(NHC)2(4,4'-bipyridine)](BF4)2 [5](BF4)2 were obtained via abstraction of the chloro ligand from 1 and reaction with the appropriate amine. Reaction of 1 with AgBF4 in the presence of PPh3 instead of an amine led to an inseparable product mixture of the mixed NHC=PPh3 complex [6]BF4, the dicarbene complex [Au(NHC)2]BF4, [7]BF4, and [Au(PPh3)2]BF4, [8]BF4. Crystals of 2 and [6]BF4 were obtained, and X-ray diffraction structure analyses revealed that the gold(I) atoms are coordinated in a linear fashion by the NHC and the co-ligand

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14

Bortoluzzi, Marco, Eleonora Ferretti, Fabio Marchetti, Guido Pampaloni i Stefano Zacchini. "Coordination complexes of niobium and tantalum pentahalides with a bulky NHC ligand". Dalton Transactions 45, nr 16 (2016): 6939–48. http://dx.doi.org/10.1039/c6dt00533k.

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Tresin, Federica, Valentina Stoppa, Marco Baron, Andrea Biffis, Alfonso Annunziata, Luigi D’Elia, Daria Maria Monti i in. "Synthesis and Biological Studies on Dinuclear Gold(I) Complexes with Di-(N-Heterocyclic Carbene) Ligands Functionalized with Carbohydrates". Molecules 25, nr 17 (24.08.2020): 3850. http://dx.doi.org/10.3390/molecules25173850.

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The design of novel metal complexes with N-heterocyclic carbene (NHC) ligands that display biological activity is an active research field in organometallic chemistry. One of the possible approaches consists of the use of NHC ligands functionalized with a carbohydrate moiety. Two novel Au(I)–Au(I) dinuclear complexes were synthesized; they present a neutral structure with one bridging diNHC ligand, having one or both heterocyclic rings decorated with a carbohydrate functionality. With the symmetric diNHC ligand, the dicationic dinuclear complex bearing two bridging diNHC ligands was also synthesized. The study was completed by analyzing the antiproliferative properties of these complexes, which were compared to the activity displayed by similar mononuclear Au(I) complexes and by the analogous bimetallic Au(I)–Au(I) complex not functionalized with carbohydrates.

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16

Bouché, Mathilde, Bruno Vincent, Thierry Achard i Stéphane Bellemin-Laponnaz. "N-Heterocyclic Carbene Platinum(IV) as Metallodrug Candidates: Synthesis and 195Pt NMR Chemical Shift Trend". Molecules 25, nr 14 (9.07.2020): 3148. http://dx.doi.org/10.3390/molecules25143148.

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A series of octahedral platinum(IV) complexes functionalized with both N-heterocyclic carbene (NHC) ligands were synthesized according to a straightforward procedure and characterized. The coordination sphere around the metal was varied, investigating the influence of the substituted NHC and the amine ligand in trans position to the NHC. The influence of those structural variations on the chemical shift of the platinum center were evaluated by 195Pt NMR. This spectroscopy provided more insights on the impact of the structural changes on the electronic density at the platinum center. Investigation of the in vitro cytotoxicities of representative complexes were carried on three cancer cell lines and showed IC50 values down to the low micromolar range that compare favorably with the benchmark cisplatin or their platinum(II) counterparts bearing NHC ligands.

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17

Goetzfried, Sina Katharina, Paul Kapitza, Caroline Marie Gallati, Anna Nindl, Monika Cziferszky, Martin Hermann, Klaus Wurst, Brigitte Kircher i Ronald Gust. "Investigations of the reactivity, stability and biological activity of halido (NHC)gold(i) complexes". Dalton Transactions 51, nr 4 (2022): 1395–406. http://dx.doi.org/10.1039/d1dt03528b.

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The significance of the halido ligand (Cl−, Br−, I−) in (NHC)gold(i) complexes in ligand exchange reactions, including the ligand scrambling to the bis(NHC)gold(i) complex 5, was evaluated by HPLC and discussed in relation to the biological activity in A2780 cell lines.

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18

Yabune, Natsuki, Hiroshi Nakajima i Takanori Nishioka. "Electronic and steric impact of bis-NHC ligands on reactions of Pt3S2 cores in trinuclear complexes bearing bis-NHC ligands with various lengths of alkylene bridges". Dalton Transactions 50, nr 35 (2021): 12079–82. http://dx.doi.org/10.1039/d1dt02747f.

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A silver(i) ion attacks the sulfide ligand of a triplatinum complex bearing ethylene-bridged bis-NHC ligands to afford a heptanuclear complex with two Ag–S bonds due to the steric hindrance of the ligands covering the Pt–Pt bonds.

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19

Warsink, Stefan, i Andreas Roodt. "trans-Bis[1-(2-benzamidoethyl)-3-(2,4,6-trimethylphenyl)imidazol-2-ylidene]dichloridopalladium(II)". Acta Crystallographica Section E Structure Reports Online 68, nr 8 (18.07.2012): m1075—m1076. http://dx.doi.org/10.1107/s1600536812031868.

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In the title compound, [PdCl2(C21H23N3O)2], the PdIIatom is located on an inversion centre and is coordinated in a slightly distorted square-planar environment by the chloride andN-heterocyclic carbene (NHC) ligands in mutualtranspositions. There are several hydrogen-bonding interactions, the most significant of which is a hydrogen bond between the amide moiety of the NHC and the chloride ligand. These hydrogen-bond interactions form a three-dimensional network.

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20

Chen, Cheng, Yang Miao, Kimmy De Winter, Hua-Jing Wang, Patrick Demeyere, Ye Yuan i Francis Verpoort. "Ruthenium-Based Catalytic Systems Incorporating a Labile Cyclooctadiene Ligand with N-Heterocyclic Carbene Precursors for the Atom-Economic Alcohol Amidation Using Amines". Molecules 23, nr 10 (20.09.2018): 2413. http://dx.doi.org/10.3390/molecules23102413.

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Transition-metal-catalyzed amide-bond formation from alcohols and amines is an atom-economic and eco-friendly route. Herein, we identified a highly active in situ N-heterocyclic carbene (NHC)/ruthenium (Ru) catalytic system for this amide synthesis. Various substrates, including sterically hindered ones, could be directly transformed into the corresponding amides with the catalyst loading as low as 0.25 mol.%. In this system, we replaced the p-cymene ligand of the Ru source with a relatively labile cyclooctadiene (cod) ligand so as to more efficiently obtain the corresponding poly-carbene Ru species. Expectedly, the weaker cod ligand could be more easily substituted with multiple mono-NHC ligands. Further high-resolution mass spectrometry (HRMS) analyses revealed that two tetra-carbene complexes were probably generated from the in situ catalytic system.

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21

Dey, Sriloy, i T. Keith Hollis. "Accessing Low-Valent Titanium CCC-NHC Complexes: Toward Nitrogen Fixation". Inorganics 9, nr 2 (8.02.2021): 15. http://dx.doi.org/10.3390/inorganics9020015.

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The dramatic expansion of the earth’s population can be directly correlated with the Haber–Bosch process for nitrogen fixation becoming widely available after World War II. The ready availability of artificial fertilizer derived thereof dramatically improved food supplies world-wide. Recently, artificial nitrogen fixation surpassed the natural process. The Haber–Bosch process is extremely energy and green-house gas intensive due to its high-temperature and H2 demands. Many low valent Ti(II) complexes of N2 are known. We report herein a preliminary investigation of the low-valent chemistry of Ti with the CCC-NHC ligand architecture. These CCC-NHC pincer Ti(IV) complexes are readily reduced with KC8 or Mg powder. Preliminary results indicate very different reactivity patterns with alkynes and phosphines for this ligand architecture versus prior ligands. Successful reduction to an intact low-valent (CCC-NHC)Ti complex was confirmed by re-oxidation with PhICl2.

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Jahnke, Mareike C., Jennifer Paley, Florian Hupka, Jan J. Weigand i F. Ekkehardt Hahn. "Silver and Gold Complexes with Benzimidazolin-2-ylidene Ligands". Zeitschrift für Naturforschung B 64, nr 11-12 (1.12.2009): 1458–62. http://dx.doi.org/10.1515/znb-2009-11-1228.

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The dicarbene silver complexes 1a, b of the type [Ag(NHC)2][AgBr2] (NHC = N,N'-dialkylbenzimidazolin- 2-ylidene) have been prepared from the parent benzimidazolium salts by reaction with silver oxide. The silver complexes have been used for the transfer of the carbene ligand to gold(I) giving the gold complexes [AuCl(NHC)] 2a, b in good yields. Crystals of 2a, b have been obtained from chloroform/pentane solutions, and X-ray diffraction structure analyses revealed gold(I) atoms coordinated in a linear fashion by an NHC carbon atom and a chloro ligand

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23

Kearney, Lauren, Michael P. Brandon, Andrew Coleman, Ann M. Chippindale, František Hartl, Ralte Lalrempuia, Martin Pižl i Mary T. Pryce. "Ligand−Structure Effects on N−Heterocyclic Carbene Rhenium Photo− and Electrocatalysts of CO2 Reduction". Molecules 28, nr 10 (17.05.2023): 4149. http://dx.doi.org/10.3390/molecules28104149.

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Three novel rhenium N−heterocyclic carbene complexes, [Re]−NHC−1−3 ([Re] = fac−Re(CO)3Br), were synthesized and characterized using a range of spectroscopic techniques. Photophysical, electrochemical and spectroelectrochemical studies were carried out to probe the properties of these organometallic compounds. Re−NHC−1 and Re−NHC−2 bear a phenanthrene backbone on an imidazole (NHC) ring, coordinating to Re by both the carbene C and a pyridyl group attached to one of the imidazole nitrogen atoms. Re−NHC−2 differs from Re−NHC−1 by replacing N−H with an N−benzyl group as the second substituent on imidazole. The replacement of the phenanthrene backbone in Re−NHC−2 with the larger pyrene gives Re−NHC−3. The two−electron electrochemical reductions of Re−NHC−2 and Re−NHC−3 result in the formation of the five−coordinate anions that are capable of electrocatalytic CO2 reduction. These catalysts are formed first at the initial cathodic wave R1, and then, ultimately, via the reduction of Re−Re bound dimer intermediates at the second cathodic wave R2. All three Re−NHC−1−3 complexes are active photocatalysts for the transformation of CO2 to CO, with the most photostable complex, Re−NHC−3, being the most effective for this conversion. Re−NHC−1 and Re−NHC−2 afforded modest CO turnover numbers (TONs), following irradiation at 355 nm, but were inactive at the longer irradiation wavelength of 470 nm. In contrast, Re−NHC−3, when photoexcited at 470 nm, yielded the highest TON in this study, but remained inactive at 355 nm. The luminescence spectrum of Re−NHC−3 is red−shifted compared to those of Re−NHC−1 and Re−NHC−2, and previously reported similar [Re]−NHC complexes. This observation, together with TD−DFT calculations, suggests that the nature of the lowest−energy optical excitation for Re−NHC−3 has π→π*(NHC−pyrene) and dπ(Re)→π*(pyridine) (IL/MLCT) character. The stability and superior photocatalytic performance of Re−NHC−3 are attributed to the extended conjugation of the π−electron system, leading to the beneficial modulation of the strongly electron−donating tendency of the NHC group.

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Bertini, Simone, i Martin Albrecht. "O-Functionalised NHC Ligands for Efficient Nickel-catalysed C–O Hydrosilylation". CHIMIA International Journal for Chemistry 74, nr 6 (24.06.2020): 483–88. http://dx.doi.org/10.2533/chimia.2020.483.

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A series of C,O-bidentate chelating mesoionic carbene nickel(ii) complexes [Ni(NHC^PhO)2] (NHC = imidazolylidene or triazolylidene) were applied for hydrosilylation of carbonyl groups. The catalytic system is selective towards aldehyde reduction and tolerant to electron-donating and -withdrawing group substituents. Stoichiometric experiments in the presence of different silanes lends support to a metal–ligand cooperative activation of the Si–H bond. Catalytic performance of the nickel complexes is dependent on the triazolylidene substituents. Butyl-substituted triazolylidene ligands impart turnover numbers up to 7,400 and turnover frequencies of almost 30,000 h-1, identifying this complex as one of the best-performing nickel catalysts for hydrosilylation and demonstrating the outstanding potential of O-functionalised NHC ligands in combination with first-row transition metals.

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Cerezo-Navarrete, Christian, Patricia Lara i Luis M. Martínez-Prieto. "Organometallic Nanoparticles Ligated by NHCs: Synthesis, Surface Chemistry and Ligand Effects". Catalysts 10, nr 10 (3.10.2020): 1144. http://dx.doi.org/10.3390/catal10101144.

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Over the last 20 years, the use of metallic nanoparticles (MNPs) in catalysis has awakened a great interest in the scientific community, mainly due to the many advantages of this kind of nanostructures in catalytic applications. MNPs exhibit the characteristic stability of heterogeneous catalysts, but with a higher active surface area than conventional metallic materials. However, despite their higher activity, MNPs present a wide variety of active sites, which makes it difficult to control their selectivity in catalytic processes. An efficient way to modulate the activity/selectivity of MNPs is the use of coordinating ligands, which transforms the MNP surface, subsequently modifying the nanoparticle catalytic properties. In relation to this, the use of N-heterocyclic carbenes (NHC) as stabilizing ligands has demonstrated to be an effective tool to modify the size, stability, solubility and catalytic reactivity of MNPs. Although NHC-stabilized MNPs can be prepared by different synthetic methods, this review is centered on those prepared by an organometallic approach. Here, an organometallic precursor is decomposed under H2 in the presence of non-stoichiometric amounts of the corresponding NHC-ligand. The resulting organometallic nanoparticles present a clean surface, which makes them perfect candidates for catalytic applications and surface studies. In short, this revision study emphasizes the great versatility of NHC ligands as MNP stabilizers, as well as their influence on catalysis.

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26

Haslinger, S., A. C. Lindhorst, J. W. Kück, M. Cokoja, A. Pöthig i F. E. Kühn. "Isocyanide substitution reactions at the trans labile sites of an iron(ii) N-heterocyclic carbene complex". RSC Advances 5, nr 104 (2015): 85486–93. http://dx.doi.org/10.1039/c5ra18270k.

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A variety of isocyanide-substituted Fe(ii) N-heterocyclic carbene (NHC) complexes has been synthesized, starting from an Fe(ii) NHC complex with an equatorial, tetradentate bis(pyridyl-NHC) ligand (NCCN).

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27

Gardiner, Michael G., David S. McGuinness i Catriona R. Vanston. "Chelated bis(NHC) complexes of saturated (imidazolin-2-ylidene) NHC ligands: structural authentication and facile ligand fragmentation". Dalton Transactions 46, nr 9 (2017): 3051–58. http://dx.doi.org/10.1039/c7dt00327g.

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Ruamps, Mirko, Stéphanie Bastin, Lionel Rechignat, Alix Sournia-Saquet, Laure Vendier, Noël Lugan, Jean-Marie Mouesca, Dmitry A. Valyaev, Vincent Maurel i Vincent César. "Redox-Switchable Behavior of Transition-Metal Complexes Supported by Amino-Decorated N-Heterocyclic Carbenes". Molecules 27, nr 12 (11.06.2022): 3776. http://dx.doi.org/10.3390/molecules27123776.

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The coordination chemistry of the N-heterocyclic carbene ligand IMes(NMe2)2, derived from the well-known IMes ligand by substitution of the carbenic heterocycle with two dimethylamino groups, was investigated with d6 [Mn(I), Fe(II)], d8 [Rh(I)], and d10 [Cu(I)] transition-metal centers. The redox behavior of the resulting organometallic complexes was studied through a combined experimental/theoretical study, involving electrochemistry, EPR spectroscopy, and DFT calculations. While the complexes [CuCl(IMes(NMe2)2)], [RhCl(COD)(IMes(NMe2)2)], and [FeCp(CO)2 (IMes(NMe2)2)](BF4) exhibit two oxidation waves, the first oxidation wave is fully reversible but only for the first complex the second oxidation wave is reversible. The mono-oxidation event for these complexes occurs on the NHC ligand, with a spin density mainly located on the diaminoethylene NHC-backbone, and has a dramatic effect on the donating properties of the NHC ligand. Conversely, as the Mn(I) center in the complex [MnCp(CO)2 ((IMes(NMe2)2)] is easily oxidizable, the latter complex is first oxidized on the metal center to form the corresponding cationic Mn(II) complex, and the NHC ligand is oxidized in a second reversible oxidation wave.

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29

Ko, Soo-Byung, Hee-Jun Park, Shaolong Gong, Xiang Wang, Zheng-Hong Lu i Suning Wang. "Blue phosphorescent N-heterocyclic carbene chelated Pt(ii) complexes with an α-duryl-β-diketonato ancillary ligand". Dalton Transactions 44, nr 18 (2015): 8433–43. http://dx.doi.org/10.1039/c4dt03085k.

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Blue phosphorescent Pt(ii) complexes that display bright blue emission in the solid state have been obtained employing NHC-based C^∧C*-chelate ligands and an α-duryl-β-diketonato ancillary ligand that provides steric blocking to minimize intermolecular interactions.

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30

NGUYEN, T. A. N., T. P. L. HUYNH, T. X. P. VO, T. H. TRAN, D. S. TRAN, T. H. DANG i T. Q. DUONG. "Structures, Energies, and Bonding Analysis of Monoaurated Complexes with N-Heterocyclic Carbene and Analogues". ASEAN Journal on Science and Technology for Development 32, nr 1 (4.07.2017): 1. http://dx.doi.org/10.29037/ajstd.8.

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In this work, we computationally investigated from quantum chemical calculations (DFT) at the BP86 level with the various basis sets def2-SVP, def2-TZVPP, and TZ2P+, chemical bonding issues of the recently described carbene-analogues gold(I) complexes AuCl-NHEMe (Au1-NHE) with E = C – Pb. The optimized structures and the metal-ligand bond dissociation energy (BDE) were calculated, and the nature of the E→Au bond was studied with charge and energy decomposition methods. The equilibrium structures of the system showed that there were major differences in the bonded orientation from the ligands NHC-NHPb to gold(I) complex between the lighter and the heavier homologues. The BDEs results showed that the metal-carbene analogues bonds were very strong bonds and the strongest bond was calculated for Au1-NHC which had the bond strength De = 79.2 kcal/mol. Bonding analysis of Au1-NHE showed that NHE ligands exhibited donor-acceptor bonds with the σ lone pair electrons of NHE donated into the vacant orbital of the acceptor fragment (AuCl). The EDA-NOCV results indicated that the ligand NHE in Au1-NHE complexes were strong σ-donors and very weak π donor and the bond order in complexes was Au1-NHC > Au1-NHSi > Au1-NHGe > Au1-NHSn > Au1-NHPb. We also realised that the gold-ligand bond was characterized by a π back-donation component from the Au to the ligand. All investigated complexes in this study were suitable targets for synthesis and gave a challenge in designing Au nano-crystals of narrow size distribution from gold(I) complexes that carried versatile N-heterocyclic carbene-analogues NHE.

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31

Poater, Albert. "Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes". Beilstein Journal of Organic Chemistry 12 (22.01.2016): 117–24. http://dx.doi.org/10.3762/bjoc.12.13.

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Bearing the versatility of N-heterocyclic carbene (NHC) ligands, here density functional theory (DFT) calculations unravel the capacity of coordination of a deprotonated NHC ligand (pNHC) to generate a doubly C2,N3-bridged dinuclear complex. Here, in particular the discussion is based on the combination of the deprotonated 1-arylimidazol (aryl = mesityl (Mes)) with [M(cod)(μ-Cl)] (M = Ir, Rh) generated two geometrical isomers of complex [M(cod){µ-C3H2N2(Mes)-κC2,κN3}]2). The latter two isomers display conformations head-to-head (H-H) and head-to-tail (H-T) of C S and C 2 symmetry, respectively. The isomerization from the H-H to the H-T conformation is feasible, whereas next substitutions of the cod ligand by CO first, and PMe3 later confirm the H-T coordination as the thermodynamically preferred. It is envisaged the exchange of the metal, from iridium to rhodium, confirming here the innocence of the nature of the metal for such arrangements of the bridging ligands.

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32

Nakano, Yuki, Satoki Shimizu, Chihiro Takeda i Satoshi Sakaguchi. "Reversal of Enantioselectivity in the Conjugate Addition Reaction of Cyclic Enones with the CuOTf/Azolium Catalytic System". Molecules 26, nr 11 (4.06.2021): 3404. http://dx.doi.org/10.3390/molecules26113404.

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Hydroxyamide-functionalized azolium salt (NHC•HI 4) was evaluated for dual enantioselective control in a Cu-catalyzed asymmetric conjugate addition (ACA) reaction. This investigation was based on our previously reported ACA reaction catalyzed using CuOTf combined with NHC•AgI complex 1. It was revealed that the stereocontrol of the catalytic ACA reaction depended on the order of the addition of the substrates. Additionally, the chiral NHC ligand precursors, substrates, the relationship between the catalyst ee (eecat) and product ee (eepro), and halogen counter anion were completely evaluated. These results suggested that the catalytic performance of the CuOTf/4 system was comparable with that of the CuOTf/1 system. Furthermore, to gain knowledge of the Cu species generated using CuOTf and NHC ligand precursor, the reaction of CuOTf with 1 was investigated. Although obtaining the corresponding NHC•CuX species failed, the corresponding NHC•AuCl complex 11 could be synthesized by allowing 1 to react with AuCl•SMe2.

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33

Gonell, S., M. Poyatos i E. Peris. "Pincer-CNC mononuclear, dinuclear and heterodinuclear Au(iii) and Pt(ii) complexes supported by mono- and poly-N-heterocyclic carbenes: synthesis and photophysical properties". Dalton Transactions 45, nr 13 (2016): 5549–56. http://dx.doi.org/10.1039/c6dt00198j.

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The photophysical properties of a family of cyclometallated Au(iii) and Pt(ii) complexes containing a CNC-pincer ligand supported by pyrene-based mono- or bis-NHC ligands are described, and compared with those shown by related dimetallic complexes of Pt/Au and Ru₂.

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34

Mimura, Shohei, Sho Mizushima, Yohei Shimizu i Masaya Sawamura. "Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands". Beilstein Journal of Organic Chemistry 16 (31.03.2020): 537–43. http://dx.doi.org/10.3762/bjoc.16.50.

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A chiral phenol–NHC ligand enabled the copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters. The phenol moiety of the chiral NHC ligand played a critical role in producing the enantiomerically enriched products. The catalyst worked well for various (Z)-isomer substrates. Opposite enantiomers were obtained from (Z)- and (E)-isomers, with a higher enantiomeric excess from the (Z)-isomer.

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35

Haziz, Umie Fatihah Mohamad, Rosenani Anwarul Haque, Al-Ashraf Abdullah Amirul i Mohd Rizal Razali. "Open Chain Tetrabenzimidazolium Salts as Ligand Precursors for Silver(I)-<i>N</i>- Heterocyclic Carbene Complexes: Synthesis, Crystal Structure and Antibacterial Studies". Materials Science Forum 1061 (26.05.2022): 217–26. http://dx.doi.org/10.4028/p-8101h0.

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The synthesis of four silver (I)-N-heterocyclic carbene (NHC) complexes bearing tetrabenzimidazol-2-yl ligands is described. The ligand precursors, open-chain tetrabenzimidazolium salts 1-4 was synthesized by the reaction between 3-(2-bromoethyl)-1-alkylbenzimidazole bromide (alkyl = ethyl, n-propyl, n-butyl, n-benzyl), i-iv with 1,2-ethylbisbenzimidazole in 2:1 molar ratio. Furthermore, their respective silver (I)-NHC complexes Ag1-Ag4 were synthesized via in-situ deprotonation method of the salts with silver oxide in 1:4 molar ratio. The synthesis of all salts and complexes were suggested by melting point, elemental analysis, FTIR studies, 1H and 13C NMR spectra. The reported silver (I)-NHC complexes with tetrabenzimidazol-2-ylidene ligands, Ag5 did not form the expected tetranuclear silver (I)-NHC complexes with the formula of [Ag4(μ4-NHC)2]∙4PF6, but the dinuclear silver (I)-NHC complexes with the formula of [Ag2(μ-NHC)]∙2PF6 was obtained, even after the changes in the molar ratio of the tetrabenzimidazolium salts and metal source. Benzimidazolium salt used as a precursor to synthesize Ag5 is similar to the structures of benzimidazolium salts 1-4, only with the different middle linker; butylene instead of ethylene chain for 1-4. Hence, we proposed that the structure of Ag1-Ag4 is similar to the structure of Ag5, suggested by spectral and elemental studies. From antibacterial study against E. coli (ATCC 25922) and S. aureus (ATCC 12600), all silver (I)-NHC complexes, Ag1-Ag4, show medium to higher activities against both bacteria compared to the standard antibiotic drug, ampicillin, while complexes Ag3 possessed the highest activity among all.

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36

Simler, Thomas, Andreas A. Danopoulos i Pierre Braunstein. "Non-symmetrical, potentially redox non-innocent imino NHC pyridine ‘pincers’ via a zinc ion template-assisted synthesis". Dalton Transactions 46, nr 18 (2017): 5955–64. http://dx.doi.org/10.1039/c7dt01014a.

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A Zn^II-promoted modular synthesis allows access to new non-symmetrical, redox-active imino NHC pyridine pincer ligands. Radical anionic and dianionic redox states of the ligand are involved in its Fe^II complexes obtained from FeBr₂/KC₈.

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37

He, Fen, Xin Yang, Zhi-Yue Tian, Han-Guang Wang i Ying Xue. "Theoretical investigation on the structures and bonding properties of Pd(II), Pt(II) and Ni(II) complexes with tridentate CNC-pincer N-heterocyclic carbene ligands". Journal of Theoretical and Computational Chemistry 15, nr 05 (sierpień 2016): 1650037. http://dx.doi.org/10.1142/s0219633616500371.

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The density functional theory (DFT) has been applied for the analysis of the bond between group 10 metals and N-heterocyclic carbene (NHC) in complexes (MCl(L-X): M [Formula: see text] Pd(II), Pt(II), and Ni(II), L-X[Formula: see text][2-(3-methylimidazolin-4,5-bisX-2-yliden-1-yl)-4-phenyl] amido, X [Formula: see text]H, Cl and CN). Full geometry optimizations have been performed for all the ligands (L-X[Formula: see text] anions), MCl[Formula: see text] cations, and the complexes. In the ligands, the energy levels of the carbon [Formula: see text] lone-pair orbitals suggest the trend L-H[Formula: see text] L-Cl[Formula: see text] L-CN[Formula: see text] for the donor strength. The role of the M–NHC interaction in complexes was investigated by natural bond orbital (NBO) analysis. The results show that the NHC–M bond consists of the components originating from the L[Formula: see text]M donation and the M[Formula: see text]Carbene C back-donation and the metal[Formula: see text]the ring of NHC back-donation. The transition-metal strongly affects the donation and back-donation. The interaction between the metal and the NHC ligand can be influenced by the central metal and the substituent on the ring of NHC.

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38

Glessi, Cristiano, Aya Mahgoub, Cornelis W. Hagen i Mats Tilset. "Gold(I) N-heterocyclic carbene precursors for focused electron beam-induced deposition". Beilstein Journal of Nanotechnology 12 (17.03.2021): 257–69. http://dx.doi.org/10.3762/bjnano.12.21.

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Seven gold(I) N-heterocyclic carbene (NHC) complexes were synthesized, characterized, and identified as suitable precursors for focused electron beam-induced deposition (FEBID). Several variations on the core Au(NHC)X moiety were introduced, that is, variations of the NHC ring (imidazole or triazole), of the alkyl N-substituents (Me, Et, or iPr), and of the ancillary ligand X (Cl, Br, I, or CF3). The seven complexes were tested as FEBID precursors in an on-substrate custom setup. The effect of the substitutions on deposit composition and growth rate indicates that the most suitable organic ligand for the gold precursor is triazole-based, with the best deposit composition of 15 atom % gold, while the most suitable anionic ligand is the trifluoromethyl group, leading to a growth rate of 1 × 10−2 nm3/e−.

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39

Zeng, Lihua, Shujian Sun, Zhang-Wen Wei, Yu Xin, Liping Liu i Jianyong Zhang. "Confinement of a Au–N-heterocyclic carbene in a Pd6L12 metal–organic cage". RSC Advances 10, nr 64 (2020): 39323–27. http://dx.doi.org/10.1039/d0ra07509d.

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40

Tegeder, Patricia, Marcello Marelli, Matthias Freitag, Laura Polito, Sebastian Lamping, Rinaldo Psaro, Frank Glorius, Bart Jan Ravoo i Claudio Evangelisti. "Metal vapor synthesis of ultrasmall Pd nanoparticles functionalized with N-heterocyclic carbenes". Dalton Transactions 47, nr 36 (2018): 12647–51. http://dx.doi.org/10.1039/c8dt02535e.

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The synthesis of N-heterocyclic carbene (NHC)-stabilized palladium nanoparticles (PdNPs) by an entirely new strategy comprising the NHC functionalization of ligand-free PdNPs obtained by metal vapor synthesis is described.

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41

Lázaro, Guillermo, Francisco J. Fernández-Alvarez, Julen Munárriz, Víctor Polo, Manuel Iglesias, Jesús J. Pérez-Torrente i Luis A. Oro. "Orthometallation of N-substituents at the NHC ligand of [Rh(Cl)(COD)(NHC)] complexes: its role in the catalytic hydrosilylation of ketones". Catalysis Science & Technology 5, nr 3 (2015): 1878–87. http://dx.doi.org/10.1039/c4cy01556h.

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Orthometallation of one N-substituent of the NHC ligand in Rh-NHC species affords hydrido-bridged binuclear rhodium(iii) complexes which have proven to be resting states in catalytic ketone hydrosilylation reactions.

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42

Yamamoto, Carlos D., Zijie Zhang i Sabine Chantal E. Stieber. "Crystal structure of (η4-cyclooctadiene)(3,3′-dimesityl-1,1′-methylenediimidazoline-2,2′-diylidene)nickel(0) tetrahydrofuran monosolvate". Acta Crystallographica Section E Crystallographic Communications 74, nr 10 (7.09.2018): 1396–99. http://dx.doi.org/10.1107/s2056989018012252.

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The crystal structure of the title compound, [Ni(C25H28N4)(C8H12)]·C4H8O or (MesNHC2Me)Ni(COD), which contains a bidentate N-heterocyclic carbene (NHC) ligand with mesityl aryl groups is reported. The complex at 100 K has monoclinic (P21/c) symmetry and a distorted tetrahedral geometry around the nickel center, with the cyclooctadiene ligand coordinated in a κ2,η2 fashion. The bidentate NHC ligand is not planar, with a C(carbene)—Ni—C(carbene) angle of 91.51 (12)°, resulting in the mesityl groups being on the same side of the cyclooctadiene (COD) ligand. One molecule of tetrahydrofuran (THF) is co-crystallized with the nickel complex and has positional disorder.

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43

Jamil, Mohamad Shazwan Shah, Sultan Alkaabi i Alan K. Brisdon. "Simple NMR predictors of catalytic hydrogenation activity for [Rh(cod)Cl(NHC)] complexes featuring fluorinated NHC ligands". Dalton Transactions 48, nr 25 (2019): 9317–27. http://dx.doi.org/10.1039/c9dt01219b.

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¹³C and ⁷⁷Se NMR parameters for fluorinated NHC ligand precursors provide simple measures of the catalytic transfer-hydrogenation reactivity of the corresponding [Rh(cod)Cl(NHC)] complexes.

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44

Heidrich, Maximillian, i Herbert Plenio. "Efficient [(NHC)Au(NTf2)]-catalyzed hydrohydrazidation of terminal and internal alkynes". Beilstein Journal of Organic Chemistry 16 (26.08.2020): 2080–86. http://dx.doi.org/10.3762/bjoc.16.175.

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The efficient hydrohydrazidation of terminal (6a–r, 18 examples, 0.1–0.2 mol % [(NHC)Au(NTf2)], T = 60 °C) and internal alkynes (7a–j, 10 examples, 0.2–0.5 mol % [(NHC)Au(NTf2)], T = 60–80 °C) utilizing a complex with a sterically demanding bispentiptycenyl-substituted NHC ligand and the benign reaction solvent anisole, is reported.

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45

Zhu, Yan-Qiu, Rui Zhang, Wei Sang, Hua-Jing Wang, Yuan Wu, Bao-Yi Yu, Jun-Chao Zhang, Hua Cheng i Cheng Chen. "Ligand-controlled palladium catalysis enables switch between mono- and di-arylation of primary aromatic amines with 2-halobenzothiazoles". Organic Chemistry Frontiers 7, nr 15 (2020): 1981–90. http://dx.doi.org/10.1039/d0qo00361a.

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46

Karabıyık, Hande, Beyhan Yiğit, Murat Yiğit, İsmail Özdemir i Hasan Karabıyık. "Enhanced π-back-donation resulting in the trans labilization of a pyridine ligand in an N-heterocyclic carbene (NHC) PdII precatalyst: a case study". Acta Crystallographica Section C Structural Chemistry 75, nr 7 (14.06.2019): 941–50. http://dx.doi.org/10.1107/s2053229619007745.

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The molecular structure of the benzimidazol-2-ylidene–PdCl2–pyridine-type PEPPSI (pyridine-enhanced precatalyst, preparation, stabilization and initiation) complex {1,3-bis[2-(diisopropylamino)ethyl]benzimidazol-2-ylidene-κC 2}dichlorido(pyridine-κN)palladium(II), [PdCl2(C5H5N)(C23H40N4)], has been characterized by elemental analysis, IR and NMR spectroscopy, and natural bond orbital (NBO) and charge decomposition analysis (CDA). Cambridge Structural Database (CSD) searches were used to understand the structural characteristics of the PEPPSI complexes in comparison with the usual N-heterocyclic carbene (NHC) complexes. The presence of weak C—H...Cl-type hydrogen-bond and π–π stacking interactions between benzene rings were verified using NCI plots and Hirshfeld surface analysis. The preferred method in the CDA of PEPPSI complexes is to separate their geometries into only two fragments, i.e. the bulky NHC ligand and the remaining fragment. In this study, the geometry of the PEPPSI complex is separated into five fragments, namely benzimidazol-2-ylidene (Bimy), two chlorides, pyridine (Py) and the PdII ion. Thus, the individual roles of the Pd atom and the Py ligand in the donation and back-donation mechanisms have been clearly revealed. The NHC ligand in the PEPPSI complex in this study acts as a strong σ-donor with a considerable amount of π-back-donation from Pd to Ccarbene. The electron-poor character of PdII is supported by π-back-donation from the Pd centre and the weakness of the Pd—N(Py) bond. According to CSD searches, Bimy ligands in PEPPSI complexes have a stronger σ-donating ability than imidazol-2-ylidene ligands in PEPPSI complexes.

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47

Bauer, Elisabeth B., Marco A. Bernd, Max Schütz, Jens Oberkofler, Alexander Pöthig, Robert M. Reich i Fritz E. Kühn. "Synthesis, characterization, and biological studies of multidentate gold(i) and gold(iii) NHC complexes". Dalton Transactions 48, nr 44 (2019): 16615–25. http://dx.doi.org/10.1039/c9dt03183a.

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The synthesis and characterization of a novel macrocyclic Au(iii) N-heterocyclic carbene (NHC) complex, a novel macrocyclic tetra-NHC benzimidazole ligand, and the corresponding Ag(i) and Au(i) complexes and initial biological studies are presented.

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48

Xiong, Yun, Shenglai Yao i Matthias Driess. "Coordination of N-Heterocyclic Carbene to H2SiX2 (X = Cl, OTf) and H3SiOTf (OTf = OSO2CF3): Synthesis of Donor-stabilized Parent Silylium Salts with Four- and Five-coordinate Silicon Atoms". Zeitschrift für Naturforschung B 68, nr 5-6 (1.06.2013): 445–52. http://dx.doi.org/10.5560/znb.2013-3057.

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The reactivity of the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazol-2- ylidene towards dichlorosilane H2SiCl2, bis(trifluoromethanesulfonato)silane H2Si(OTf)2 (OTf = OSO2CF3), and silyl trifluoromethanesulfonate H3SiOTf has been investigated. It turned out that the coordination of the NHC ligand can occur stepwise to form the three neutral compounds (NHC)SiH2Cl2 (1), (NHC)2SiH2Cl2 (2), (NHC)SiH2(OTf)2 (3), as well as the two ion pairs [(NHC)SiH3]+(OTf-) (4) and [(NHC)2SiH3]+(OTf-) (5); the latter represent the first NHC adducts of the parent silylium cation (H3Si+). The multinuclear NMR and IR spectroscopic data of the products reflect the characteristics of four-, five-, and six-coordinate silane complexes. All new compounds were structurally characterized by single-crystal X-ray diffraction analyses

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49

Sase, Shohei, Yuriko Ikehara i Kei Goto. "Crystal structure of {3-[3,5-bis(2,6-dimethylphenyl)-1,2-phenylene]-1-(2,6,2′′,6′′-tetramethyl-1,1′:3′,1′′-terphenyl-5′-yl)imidazol-2-ylidene}chlorido(η6-p-cymene)ruthenium(II) benzene disolvate". Acta Crystallographica Section E Structure Reports Online 70, nr 12 (8.11.2014): m394. http://dx.doi.org/10.1107/s160053681402399x.

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The title compound, [Ru(C47H43N2)Cl(C10H14)]·2C6H6, crystallized with two independent molecules of benzene. One of theN-aryl moieties of theN-heterocyclic carbene (NHC) ligand underwent cyclometallation to form a five-membered ruthenacycle. The complex has a three-legged piano-stool structure with two C atoms incorporated in the five-membered ruthenacycle and a Cl atom as legs. The ruthenacycle is essentially coplanar with the imidazole ring of the NHC ligand, making a dihedral angle of 0.85 (8)°.

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50

Renom Carrasco, Marc, Clémence Nikitine, Mohamed Hamou, Claude de Bellefon, Chloé Thieuleux i Valérie Meille. "Self-Metathesis of Methyl Oleate Using Ru-NHC Complexes: A Kinetic Study". Catalysts 10, nr 4 (17.04.2020): 435. http://dx.doi.org/10.3390/catal10040435.

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A kinetic study concerning the self-metathesis of methyl oleate and methyl elaidate was performed, using a variety of NHC-ruthenium pre-catalysts, bearing either mesityl groups or di-isopropyl-phenyl groups on the NHC ligand and various trans ligands with respect to the NHC unit. We showed that the system can be satisfactorily described using one initiation constant per pre-catalyst and four propagation constants that, conversely, do not depend on the pre-catalyst. The difference of reactivity with oleate (Z) and elaidate (E) can be fully explained by the propagation parameters; the studied pre-catalysts initiate with the same rate starting from the Z or the E olefin. The ranking of the propagation parameters is driven by the thermodynamic equilibrium. The transformation rates of Z and E isomers is only driven by these propagation constants and nothing differentiates the initiation step.

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