To see the other types of publications on this topic, follow the link: Metallocenes.
Dissertations / Theses on the topic 'Metallocenes'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Metallocenes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Charpentier, Paul A. "Metallocene-catalyzed semi-batch and continuous polymerization of ethylene /." *McMaster only, 1997.
Find full text
2
Mokdsi, George. "Antitumour Metallocenes." Thesis, The University of Sydney, 2000. http://hdl.handle.net/2123/794.
Full textAbstract:
This thesis reports a study of the chemical stability and coordination chemistry of several antitumour metallocenes Cp2MCl2 (Cp = h5-C5H5; M = Ti 1, V 2, Nb 3, Mo 4), as well as derivatives of Cp2TiCl2 1, with nucleic acids, nucleic acid constituents and proteins. These studies were carried out in order to identify the biologically active species and more fully understand the molecular level mechanism of action of the antitumour metallocenes, in particular Cp2TiCl2 1, which is currently undergoing phase II clinical trials. The interactions of Cp2MoCl2 4 with four oligonucleotides were studied by 1H and 31P NMR spectroscopy. In 50 mM salt solutions of Cp2MoCl2 4, hydrolysis of the halide ligands occurred to give a solution with pD -2, containing a species in which both Cp rings remain metal bound for 24 h. At pD -7, partial hydrolysis of the Cp rings (-30percent) occurred after 24 h. Addition of an aqueous solution of Cp2MoCl2 4 in 50 mM salt to the self-complementary sequence d(CGCATATGCG)2, maintaining the pD at 6.0-7.0, showed no evidence for the formation of a metallocene-oligonucleotide complex and only peaks arising from hydrolysis of Cp2MoCl2 4 were detected. A similar result was obtained in titration experiments with the single stranded sequence d(ATGGTA) at pD 6.5-7.0. However, at pD 3.0, new signals assigned to a molybdocene-oligonucleotide complex(es), which was stable for hours at pD 3.0, were detected; while at pD -7 the complex is destabilised and only peaks arising from hydrolysis of Cp2MoCl2 4 were detected. Titration experiments at low pD with Cp2MoCl2 4 and the dinucleotide dCG were consistent with formation of a complex arising due to coordination of molybdenum to guanine N7 and/or cytosine N3. The results obtained showed that stable oligonucleotide adducts were not formed in 50 mM salt at pD -7 and hence it is highly unlikely that formation of molybdocene-DNA adducts in vivo is the primary action that is responsible for the antitumour properties of Cp2MoCl2 4. The rate of hydrolysis of the aromatic rings of Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) and the dimethylsubstituted derivatives (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41), in aqueous solutions at pD 2-8 was studied by 1H NMR spectroscopy. Rapid hydrolysis of both the halide/glycine and Cp ligands in Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) occurred and predominantly gave a precipitate at pD -7. In contrast, under the same experimental conditions, the predominant species present in aqueous solutions of (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) at pH 2-8 contained both MeCp rings metal bound. At pD < 5, Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) and (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) formed similar complex(es) with purine nucleotides. However, at pD >5, stable adducts between nucleotides and Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) were not formed. In contrast, (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) formed complex(es) with 5'-dAMP or 5'-dGMP, which were stable for 24 h. These results suggest that formation of stable chelates between (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) and nucleic acid constituents in vivo is possible. However, the methyl substituted derivatives 34 and 41 did not show any antitumour activity against EAT in mice when administered in either 10percentDMSO/90percentsaline or in water at pH 6.2-6.4, which suggests that the labile Cp-Ti bond present in Cp2TiCl2 1 is required for antitumour activity. The synthesis of a range of Cp substituted titanocene derivatives was investigated in an attempt to prepare derivatives with modified Cp stability in comparison to the methyl substituted derivatives. The synthesis of derivatives (CpCH2Y)2TiCl2 where Y equals ?CHO 43, ?CONMe2 44, ?NO2 45, (RCp)2TiCl2 where R equals ?COMe 46, ?COOMe 47 or ?CONMe2 48, (CpNMe2)2TiCl2 62 and (Cp(CH2)2NMe2)2TiCl2 63 was unsuccessful, due to the presence of coordinating substituents on the Cp rings and poor stability in polar, protic solvents. Hence, these derivatives were excluded from further studies. The rate of hydrolysis of the Cp rings of Cp2TiX2 (X equals Cl 1, OCOCCl3 22 and OCOCH2NH3Cl 27) in aqueous solutions, 10percentDMSO/90percentD2O and 100percent DMSO was monitored by 1H NMR spectroscopy. Rapid hydrolysis of both the carboxylate and Cp ligands of Cp2TiX2 (OCOCCl3 22 and OCOCH2NH3Cl 27) occurred in DMSO to give biologically inactive species. The rate of these reactions were concentration dependent as dilution of these samples with saline or water to give the therapeutic conditions of 10percentDMSO/90percentD2O slowed the hydrolysis chemistry. In contrast, samples of Cp2TiX2 (X equals Cl 1 and OCOCH2NH3Cl 27) dissolved in water, gave solutions containing the presumed antitumour active species in which the halide or glycine ligands have been hydrolysed but the Cp rings remain metal bound. Thus, charged X ligands may be incorporated into Cp2TiX2 and will give comparable activity to Cp2TiCl2 1 provided the samples are administered in water. The antitumour metallocenes Cp2MCl2 (M equals Ti 1, V 2, Nb 3, Mo 4) and the inactive derivative (MeCp)2TiCl2 34 were found to inhibit the relaxation of supercoiled plasmid DNA pBR322 by human topoisomerase II in vitro. These results implicated the inhibition of topoisomerase II in the mechanism of antitumour activity although there was no direct correlation between the in vitro results with biological activity against EAT in vivo. UV spectroscopy confirmed that the metallocenes Cp2MCl2 (M equals Ti 1, Mo 4) became associated with and were stabilised to hydrolysis by calf thymus DNA but not with human serum albumin. ICP-AES was used to measure the amount of metal associated with either DNA or human serum albumin after incubation with Cp2MCl2 (M equals Ti 1, Nb 3, Mo 4) and dialysis of these solution. The results confirmed that DNA stabilises or becomes associated with the metallocenes. However, errors associated with the ICP-AES measurements did not allow these results to be quantified. 1H NMR spectroscopy was used to show that the antitumour metallocene Cp2MoCl2 4 formed an adduct with glutathione 72 in the pH range 3-7 through the sulfur donor group. In comparison, the antitumour metallocenes Cp2MCl2 (M equals Ti 1, Nb 3) showed limited adduct formation with glutathione 72 at pH -3 and no adducts were detected at pH > 5.5.
3
Mokdsi, George. "Antitumour Metallocenes." University of Sydney. Chemistry, 2000. http://hdl.handle.net/2123/794.
Full textAbstract:
This thesis reports a study of the chemical stability and coordination chemistry of several antitumour metallocenes Cp2MCl2 (Cp = h5-C5H5; M = Ti 1, V 2, Nb 3, Mo 4), as well as derivatives of Cp2TiCl2 1, with nucleic acids, nucleic acid constituents and proteins. These studies were carried out in order to identify the biologically active species and more fully understand the molecular level mechanism of action of the antitumour metallocenes, in particular Cp2TiCl2 1, which is currently undergoing phase II clinical trials. The interactions of Cp2MoCl2 4 with four oligonucleotides were studied by 1H and 31P NMR spectroscopy. In 50 mM salt solutions of Cp2MoCl2 4, hydrolysis of the halide ligands occurred to give a solution with pD -2, containing a species in which both Cp rings remain metal bound for 24 h. At pD -7, partial hydrolysis of the Cp rings (-30percent) occurred after 24 h. Addition of an aqueous solution of Cp2MoCl2 4 in 50 mM salt to the self-complementary sequence d(CGCATATGCG)2, maintaining the pD at 6.0-7.0, showed no evidence for the formation of a metallocene-oligonucleotide complex and only peaks arising from hydrolysis of Cp2MoCl2 4 were detected. A similar result was obtained in titration experiments with the single stranded sequence d(ATGGTA) at pD 6.5-7.0. However, at pD 3.0, new signals assigned to a molybdocene-oligonucleotide complex(es), which was stable for hours at pD 3.0, were detected; while at pD -7 the complex is destabilised and only peaks arising from hydrolysis of Cp2MoCl2 4 were detected. Titration experiments at low pD with Cp2MoCl2 4 and the dinucleotide dCG were consistent with formation of a complex arising due to coordination of molybdenum to guanine N7 and/or cytosine N3. The results obtained showed that stable oligonucleotide adducts were not formed in 50 mM salt at pD -7 and hence it is highly unlikely that formation of molybdocene-DNA adducts in vivo is the primary action that is responsible for the antitumour properties of Cp2MoCl2 4. The rate of hydrolysis of the aromatic rings of Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) and the dimethylsubstituted derivatives (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41), in aqueous solutions at pD 2-8 was studied by 1H NMR spectroscopy. Rapid hydrolysis of both the halide/glycine and Cp ligands in Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) occurred and predominantly gave a precipitate at pD -7. In contrast, under the same experimental conditions, the predominant species present in aqueous solutions of (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) at pH 2-8 contained both MeCp rings metal bound. At pD < 5, Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) and (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) formed similar complex(es) with purine nucleotides. However, at pD >5, stable adducts between nucleotides and Cp2TiX2 (X equals Cl 1, OCOCH2NH3Cl 27) were not formed. In contrast, (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) formed complex(es) with 5'-dAMP or 5'-dGMP, which were stable for 24 h. These results suggest that formation of stable chelates between (MeCp)2TiX2 (X equals Cl 34, OCOCH2NH3Cl 41) and nucleic acid constituents in vivo is possible. However, the methyl substituted derivatives 34 and 41 did not show any antitumour activity against EAT in mice when administered in either 10percentDMSO/90percentsaline or in water at pH 6.2-6.4, which suggests that the labile Cp-Ti bond present in Cp2TiCl2 1 is required for antitumour activity. The synthesis of a range of Cp substituted titanocene derivatives was investigated in an attempt to prepare derivatives with modified Cp stability in comparison to the methyl substituted derivatives. The synthesis of derivatives (CpCH2Y)2TiCl2 where Y equals ?CHO 43, ?CONMe2 44, ?NO2 45, (RCp)2TiCl2 where R equals ?COMe 46, ?COOMe 47 or ?CONMe2 48, (CpNMe2)2TiCl2 62 and (Cp(CH2)2NMe2)2TiCl2 63 was unsuccessful, due to the presence of coordinating substituents on the Cp rings and poor stability in polar, protic solvents. Hence, these derivatives were excluded from further studies. The rate of hydrolysis of the Cp rings of Cp2TiX2 (X equals Cl 1, OCOCCl3 22 and OCOCH2NH3Cl 27) in aqueous solutions, 10percentDMSO/90percentD2O and 100percent DMSO was monitored by 1H NMR spectroscopy. Rapid hydrolysis of both the carboxylate and Cp ligands of Cp2TiX2 (OCOCCl3 22 and OCOCH2NH3Cl 27) occurred in DMSO to give biologically inactive species. The rate of these reactions were concentration dependent as dilution of these samples with saline or water to give the therapeutic conditions of 10percentDMSO/90percentD2O slowed the hydrolysis chemistry. In contrast, samples of Cp2TiX2 (X equals Cl 1 and OCOCH2NH3Cl 27) dissolved in water, gave solutions containing the presumed antitumour active species in which the halide or glycine ligands have been hydrolysed but the Cp rings remain metal bound. Thus, charged X ligands may be incorporated into Cp2TiX2 and will give comparable activity to Cp2TiCl2 1 provided the samples are administered in water. The antitumour metallocenes Cp2MCl2 (M equals Ti 1, V 2, Nb 3, Mo 4) and the inactive derivative (MeCp)2TiCl2 34 were found to inhibit the relaxation of supercoiled plasmid DNA pBR322 by human topoisomerase II in vitro. These results implicated the inhibition of topoisomerase II in the mechanism of antitumour activity although there was no direct correlation between the in vitro results with biological activity against EAT in vivo. UV spectroscopy confirmed that the metallocenes Cp2MCl2 (M equals Ti 1, Mo 4) became associated with and were stabilised to hydrolysis by calf thymus DNA but not with human serum albumin. ICP-AES was used to measure the amount of metal associated with either DNA or human serum albumin after incubation with Cp2MCl2 (M equals Ti 1, Nb 3, Mo 4) and dialysis of these solution. The results confirmed that DNA stabilises or becomes associated with the metallocenes. However, errors associated with the ICP-AES measurements did not allow these results to be quantified. 1H NMR spectroscopy was used to show that the antitumour metallocene Cp2MoCl2 4 formed an adduct with glutathione 72 in the pH range 3-7 through the sulfur donor group. In comparison, the antitumour metallocenes Cp2MCl2 (M equals Ti 1, Nb 3) showed limited adduct formation with glutathione 72 at pH -3 and no adducts were detected at pH > 5.5.
4
Mäkelä-Vaarne, Nora. "Characterisation of group 4 metallocenes and metallocene catalysts : UV/VIS spectroscopic study." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/kemia/vk/makela-vaarne/.
Full text
5
Barlow, Stephen. "Studies of oligomeric metallocenes." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308613.
Full text
6
Soria-Alvarez, Carmen. "Synthetic applications of polar metallocenes." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614902.
Full text
7
Garabatos-Perera, Jose Ramon. "En route to multi-bridged metallocenes." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980450896.
Full text
8
Hill, Jeremy Nicholas. "Laser-induced fluorescence of reactive metallocenes." Thesis, University of York, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357048.
Full text
9
Stokes, Francesca Alice. "Synthetic applications of polar transition metal metallocenes." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/264975.
Full textAbstract:
Since the sandwich structure of ferrocene was elucidated in 1952, metallocenes have generated a vast amount of interest. Transition metal metallocenes have previously been shown to be suitable precursors in the syntheses of novel organometallic and metallo-organic complexes, although the use of metal halide starting materials for organometallic synthesis is much more common due to their being readily commercially available and generally easier to handle than the extremely air- and moisture-sensitive metallocene alternatives. In this project, the polar transition metal metallocenes Cp2V, Cp2Cr, Cp2Mn and Cp2Ni were employed as precursors in the synthesis of fourteen novel metal containing complexes, in several cases generating products which could not have been obtained using metal halide starting materials.
10
Spikes, Geoffrey. "Reactivity studies of some Ti-based metallocenes." Thesis, University of Sussex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398353.
Full text
11
Layfield, Richard Alan. "Structure, bonding and reactivity of polar metallocenes." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620712.
Full text
12
Nagano, Takashi. "Metathesis route to bridged metallocenes and phosphametallocenes." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/145117.
Full text
13
Diamond, Gary M. "ANSA-bridged and binuclear metallocene compounds of zirconium and hafnium." Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:297bc125-5270-4969-89c3-69fd326e5c02.
Full textAbstract:
This thesis describes the synthesis and characterisation of new mononuclear and binuclear zirconium and hafnium compounds containing ansa-bridged ligands. Some olefin polymerization studies, employing the new compounds as catalysts, are also presented. Chapter 1 begins with an introduction to Ziegler-Natta polymerization of olefins, concentrating on recently developed metallocene-based catalyst systems. The second part of the Chapter charts the development of group 4 ansa-metallocene derivatives, especially their use as stereospecific catalysts. Finally, a review of binuciear group 4 metallocene compounds containing bridging bis(cyclopentadienyl)-type ligands is presented. Chapter 2 describes the synthesis and characterisation of some novel mononuclear metallocene compounds of zirconium and hafnium containing ansa-bridged ligands. The ansa-bridged mononuclear compounds [{Me2C(η5-C5H4)(η2-C9H6)}M(η5C5H5)Cl] (M = Zr, Hf), [{(CH2)5C(η5-C5H4)(η2-C9H6)}M(η5-C5H5)Cl] (M = Zr, Hf) and [{Me2(η5-C5H4)(η3-C13H8)}Zr(η5-C5H5)Cl] are described, along with the X-ray crystal structures of the zirconium compounds. The η2-indenyl and η3-fluorenyl coordination modes observed for these compounds are unprecedented. The synthesis and characterisation of the novel, mononuclear ansa-bridged compounds [{Me2C(η5-C5H4)
14
Piper, Colin. "Synthesis and structural study of functionally substituted #eta#'5-cyclopentadienyl derivatives of transition and main group metals." Thesis, Coventry University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281883.
Full text
15
Arisandy, Christofer. "Studies of linked ferrocenes and ruthenocenes." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270251.
Full text
16
Aazam, Elham Shafik. "A study of the reactivity of the titanocene [Ti(#eta#'5-Cp's)â†2]." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391832.
Full text
17
Bachellier, Nicolas. "On surface spin detection and doping of metallocenes." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE030/document.
Full textAbstract:
Le sujet principal de cette thèse est l'étude de métallocènes déposés sur une surface de cuivre. Leurs adsorptions et propriétés électroniques sont expérimentalement étudiées par microscopie à effet tunnel (STM) et spectroscopie par effet tunnel (STS). Nos résultats ont été validés par des calculs se basant sur la théorie de la fonctionnelle de la densité (DFT). Plus précisément, nous avons étudié la façon dont le ferrocène FeC10H10 et le nickelocène NiC10H10s'adsorbent sur le cuivre. Nous avons découvert que ces métallocènes forment spontanément des réseaux alternant molécules horizontales et verticales. Nous avons ensuite modifié la structure du ferrocène par l'ajout d'un atome de cobalt et caractérisé les propriétés magnétiques de la nouvelle molécule ainsi créée, notamment l'apparition d'un effet Kondo témoignant de l'apparition de propriétés magnétiques au sein de la molécule. L'étude spectroscopique du nickelocène a révélé une excitation de la molécule à basse énergie.Cette excitation se traduit par une réorientation du moment de spin de la molécule, passant d'une orientation perpendiculaire à l'axe principal de la molécule à une orientation parallèle à cet axe.Nous avons finalement transféré un nickelocène sur la pointe STM et utilisé cette pointe moléculaire pour sonder les états d'une seconde molécule. Nous avons alors obtenu une double excitation de spin dans notre jonction tunnel, avec une augmentation significative de la conductance due aux excitationsThe main subject of this PhD thesis is the study of metallocenes deposited on copper surfaces. Their adsorptions and electronic properties are experimentally studied by scanning tunnelling microscopy(STM) and scanning tunnelling spectroscopy (STS). Our results were confirmed by density functional theory (DFT) computations. More precisely, we studied how ferrocene FeC10H10 and nickelocene NiC10H10 are adsorbed on copper. We found that these metallocenes spontaneously create networks alternating horizontal and vertical molecules. We added a cobalt atom to the ferrocene in order to modify its structure and we characterized the magnetic properties of the new molecule we created, in particular the appearance of a Kondo effect showing that magnetic properties appeared in the molecule. The spectroscopic study of nickelocene revealed an excitation of the molecule at low bias. This excitation consist in a change in the spin orientation of the molecule, going from an orientation perpendicular to the main molecule axis to an orientation parallel to this axis. We finally transferred a nickelocene to the STM tip and used this molecular tip to probe the states of a second molecule. We consequently obtained a double spin excitation in our tunnel junction, with a significant increase of the conductance due to excitations
18
Clancy, Gerald Patrick. "Synthetic inorganic chemistry : novel metallocenes and inorganic fullerenes." Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:9c7f7c35-bb8f-4117-8e2e-e56a9fbcbeab.
Full textAbstract:
This thesis is divided into two parts. The first part concerns the synthesis and characterisation of substituted metallocene complexes of the transition and main group metals. The second part describes the preparation and characterisation of inorganic fullerene (IF)-related materials. Chapter 1 reviews the chemistry of dialkyl- and diaryl-phosphino substituted cyclopentadienyl complexes of the transition metals. Chapter 2 describes the synthesis and characterisation of the new ligands [M(C5Me4)CH2PMe2] (M = H, Li, Na and K) via the precursors [HC5Me4)CH2PHMe2][X] (X = Cl and PF6). The synthesis, characterisation and chemical reactivity of the compounds [Zr{{η-C5Me4)CH2PMe2}2Cl2 and [Mn{η-C5Me4)CH2PMe2}2] is reported together with supporting evidence for the synthesis of the bimetallic complex [Zr{U+03B7-C5Me4)CH2PMe2}2Cl2PtI2] and the complex [Mn{η-C5Me4)CH2PMe2B(C6F5)3}2]. Chapter 3 provides a brief introduction into the field of main group metallocenes and describes the synthesis and characterisation of the new main group metallocenes [M{η- C5H4)CMe2PMe2}2] (M = Pb and Sn). The B(C6F5)3 adduct [Pb{η-C5H4)CMe2PMe2(B(C6F5)3}2] has also been synthesised. The main group - transition metal bimetallic complex [Pb{η-C5H4)CMe2PMe2}2PtI2 in which the substitutedplumbocene acts as a bidentate ligand, has been characterised by mass spectrometry and 31P{1H}NMR spectroscopy. Chapter 4 provides an introduction into the field of IF-related materials and an overview of the analytical techniques used in their characterisation. Chapter 5 describes the preparation and characterisation of IF-MoS2 and IF-(Nb,W)S2 materials from MoC and the binary oxides Nb8 W9O47 and Nb4W13O47 respectively. A powder X-ray diffraction study of the conversion of WC to WO3-X and the subsequent sulfidisation by H2S to form novel IF-WS2 morphologies is also described. Chapter 6 describes the preparation of amorphous Group 5 metal (V, Nb and Ta) oxides using the metal vapour synthesis technique. These amorphous precursors have been annealed in a reducing atmosphere to form the oxide phases U+03B1-V2O3, NbO2 and TT-Ta2O5 which have been identified by powder X-ray diffraction. Upon reaction with H2S, the crystalline oxides afford layered sulfides of the form MS2 (M = V, Nb and Ta), some of which exhibit behaviour typical of IF-like materials and have been characterised by HRTEM, powder X-ray diffraction and EDX analysis. Chapter 7 outlines the experimental details for the synthesis, characterisation, reactions and compounds described in the preceding chapters. Chapter 8 presents the characterising data for the new compounds described in chapters 2 and 3. Appendix A contains details of the crystallographic data for the structurally characterised compound [Mn{η-C5Me4)CHPMe2}2].
19
Hart, Suzanne L. "Synthesis and applications of chiral-at-titanium organometallic compounds." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245941.
Full text
20
Jardine, Christian N. "Density functional studies of ansa-metallocenes and related compounds." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325922.
Full text
21
Hobson, Lois J. "Extended structures of metallocenes for application in material science." Thesis, Bangor University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262452.
Full text
22
Bell, Jane Louise. "The synthesis and applications of chiral, group IV metallocenes." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336625.
Full text
23
Constantine, Steven Peter. "The preparation and characterisation of some bis-cyclopentadienyl metallocenes." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360580.
Full text
24
Rodriguez-Delgado, Antonio. "Homogeneous 1-alkene polymerisation catalysts : understanding metallocenes and exploring alternatives." Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268577.
Full textAbstract:
The optimisation of I-alkene polymerisation processes by highly active metallocene systems such as racSBIZrMe2 activated by [Ph3C][CN{B(C6Fs)3h] (I) or by [Ph3C][B(C~s)4] (II) was perfonned. Subsequently. a systematic quantitative study of ligand effects on polymerisation activity, molecular weight and polymer microstructure was carried out. Non-bridged and bridged C2y-symmetry zirconocene dimethyls and dichlorides alkylated (or alkyl exchanged) by AlBu'3 (TIBA) and activated by 1 are much less active than Crsymmetric zirconocenes. Propene polymerisations catalysed by those systems afford low molecular weight atactic polypropene. TIBA rapidly alkylates dichloride zirconocenes affording pre-catalysts which, once activated, give a catalytic profile comparable with that obtained with dimethyl zirconocenes. Activities of Crsymmetry raczirconocenes / AlBui3 / I or [Ph3C][H2N{B(C6Fs)3h] (III) in propene polymerisation decrease according to the order SBMbiZrCh (17) > SBIZrCh (16) > EBIZrCh (13) > MBBIZrCh (18) > EBIDMZrCh (19) > EBTHIZrCb (20) > SBSCZrCh (14) > SBBCZrCh (15). These values are not distorted by side effects such as mass transport limitation, so represent real activities, which are the highest reported to date for most of these catalysts under the experimental conditions fixed. The molecular weight of polypropene obtained in propene polymerisation reactions at 1 bar monomer pressure and 20°C ranges from high to low molecular weight (336000 to 4600 g/mol), decreasing according to the precatalyst, in the following order: SBMbiZrCh (17) > SBIZrCh (16) > MBBIZrCh (18) > EBIZrCh (13) > EBTHIZrCh (20) > SBsczrCh (14) > EBIDMZrCh (19) > SBBCZrCh (15). Experiments carried out at 1 bar of monomer pressure and 60°C afford polymers of medium to low molecular weight and the same trend. The order of isotacticity and regiospecificity of the polypropene obtained is: SBMbiZrCh (17) > SBSCZrCh (14) > SBBCZrCh (15) > MBBIZrCh (18) >EBIZrCh (13) > EBDMIZrCh (19) The trityl salt 1 generates more active catalysts than III for the polymerisations perfonned at 20°C, but the situation is reversed at 60 0c. The molecular weight of the polymers obtained by systems activated by III is slightly higher than those obtained using I under both experimental regimes (20 and 60°C / 1 bar). Reactions of L2ZrMe2 (where 4, L= CsMes; 6, L= CSMe4H) with III in presence of AIMe3, fonn [(~)Zr(JlMe) 2AIMe2][H2N{B(C6Fs)3h] (23, L= CsMes; 24, L= CSMe4H) whereas with I, ~ZrMe(Il-Me)B-(C6F5h and L2ZrMe(Il-NC)B-(C6FS)3 were obtained. The protolysis reaction ofY[N(SiMe3)2h with (2-C~sN=CH)(6-Bu)C6H30H (HL3 ) led to a variety of products. Y[N(SiMe3)2h(L3) (29), alongside Y[N(SiMe3)2](L3)2 (30) and Y(L3h (31) were synthesised. M(CH2SiMe3)2(THF)(Ll) (25, M = Sc; 26, M = Y; and L 1 = 2,3,6-Me3C6H3N=CH(6-Bu')C~30H) are highly effective catalysts for the ring-opening polymerisation of E-caprolactone. 26 and 30 also initiate polymerisation of cyc10hexene oxide (CHO).
25
Dai, Shuanghua Patrick. "X-ray scattering and thermal analysis study of isotactic polypropylene /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2000.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2000.Submitted to the Dept. of Physics. Adviser: Peggy Cebe. Includes bibliographical references (leaves 246-251). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
26
Lancaster, Simon John. "Synthesis, structure and catalytic activity of cationic zirconium and hafnium alkyl complexes." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297046.
Full text
27
Hodge, Andrew. "The chemistry of ruthenium and osmium σ-bound acetylides." Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/273013.
Full text
28
Osborne, James Daniel. "The synthesis of planar chiral metallocenes for application in asymmetric catalysis." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436806.
Full text
29
Kelly, Patrick A. "C₁ symmetric ansa-metallocenes via a novel 2-(Phenylsulfonyl)indane route /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
Full text
30
Bailey, Nigel J. "ANSA bridged metallocene chemistry of niobium." Thesis, University of Oxford, 1998. http://ora.ox.ac.uk/objects/uuid:9bd76a85-ba44-42d8-affe-317bc98be368.
Full textAbstract:
This thesis is concerned with the synthesis and characterisation of new ansa bridged bis-η-cyclopentadienyl derivatives of niobium. Chapter 1 provides an introduction to the area of early transition metal bent metallocene derivatives and charts the development of ansa bridged metallocenes. Chapter 2 presents the synthesis and characterisation of some new ansa niobocene derivatives prepared from niobium(IV) chloride. The compounds [Nb(η-C5H4-CMe2- η-C5H4)(η2-BH4)],* [Nb(η-C5H4-CMe2-η-C5H4)(PMe3)H],* [Nb(η-C5H4-CMe2-η- C5H4)(PPh3)H], [Nb(η-C5H4-CMe2-η-C5H4)(SPh)2] and [Nb(η-C5H4-CMe2-η- C5H4)(CH2Ph)2]* are described. An asterisk indicates that the X-ray crystal structure was determined. Chapter 3 describes the synthesis and characterisation of some ansa niobocene derivatives containing ancillary imido ligands. The compounds [Nb(η-C5H4-CMe2-η- C5H4)(NSiMe3)Cl],* [Nb(η-C5H4-CMe2-η-C5H4)(NBu')X] (X = Cl,* Br,* I,* Me), [Nb(η-C5H4-CMe2-η-C5H4)(NHBu')Cl][BF4)]and[Nb(η-C5H4-CMe2-η-C5H4)(O)Cl]* are described. An asterisk indicates that the X-ray crystal structure was determined. Photoelectron spectra were recorded for [Nb(η-C5H4-CMe2-η-C5H4)(NBu')X] (X = Cl, Me) and compared to a geometry optimisation calculation obtained using density functional theory. In these formally twenty electron compounds the HOMO has negligible metal contribution and the eighteen electron rule is not violated. Chapter 4 describes the results of a preliminary investigation into ansa niobium(III) bis-η-cyclopentadienyl derivatives containing phosphorus donor ligands. The compound [Nb(η-C5H4-CMe2-η-C5H4)(PMe3)Cl] is characterised spectroscopically. The synthesis and full characterisation details of the compound [Nb(η-C5H4-CMe2-η- C5H4){P(OMe)3}Cl] are given, including the X-ray crystal structure. Chapter 5 provides the experimental details for the preceding Chapters and Chapter 6 contains the characterising data for the new compounds described in this thesis. Full details of the X-ray crystallographic structure determinations are given in Appendices A -1.
31
Wong, Heng Vee. "Structural, electronic and kinetic studies on organometallic intercalates of metal dichalcogenides." Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:aad80a5e-a1bb-4eea-80e8-ce079e0b1204.
Full textAbstract:
Large single crystals of the metal dichalcogenide hosts ZrS2 and 811X2 (X = S, Se) have been successfully intercalated with a variety of organometallic guests {C0(η-C5H5)2, CO(η-C5H4CH3)2, Mo(η-C6H6)2, Mo(η-C7H7)(η-C5H5), W(η-C7H7)(η-C5H5), Ti(η-C8H8)(η-C5H5)}. The structural and electronic properties of these materials have been studied, as well as the intercalation kinetics of these organometallic species into the tin dichalcogenides. X-ray and neutron diffraction experiments have been used to obtain 001 reflections in order to obtain a one-dimensional profile of electron and neutron scattering in these disordered layered materials (Chapter Two). Refinement of the data shows that for all the organometallic guests, the majority of the intercalant adopts an orientation in which the principal molecular axis lies parallel to the layer planes of the host. These findings are confirmed by 2H NMR spectroscopy on single crystals of deuterated cobaltocene intercalates of ZrS2 and SnSe2, where it has been shown that rapid C5, but not C2, rotation of the metallocene occurs in the interlamellar van der Waals space. To study the electronic properties of these intercalates, electrical resistivity and magnetic susceptibility measurements have been performed (Chapter Three). An apparatus has been built to measure the resistivity of these crystal intercalates down to 4.2K. The resistivity measurements show that intercalation of various organometallic complexes confers metallic properties upon ZrS2 while SnS2{Co(η-C5H5)2} 0.3 becomes a superconductor with a Tc of 8.3K. The magnetic susceptbility measurements confirm the presence of guest-host charge transfer. Estimates of its extent, as well as the magnitude of the Pauli susceptibility in these intercalates, have been attempted. Studies on the rate and mechanism for the intercalation of cobaltocene into the disulfides and diselenides of tin have been performed (Chapter Four). An apparatus has been designed and constructed for in situ diffraction using synchrotron X-rays in order to monitor the progress of these rapid intercalation reactions. The results indicate that the rate of intercalation of cobaltocene into the tin dichalcogenides is very much dependent on the solvent used, being significantly faster in dimethoxyethane than in toluene. Analyses of the kinetic rate expressions for the tin dichalcogenide intercalation in dimethoxyethane suggests that diffusion of cobaltocene molecules into the interlamellar space constitutes the rate limiting step. The choice of solvent also dramatically affects the mechanism of the intercalation. When a solution of cobaltocene in dimethoxyethane is used, the host transforms directly to the final product but in toluene, staged intermediates are observed during the intercalation process. The apparatus and techniques that have been developed for the in situ kinetics experiments are general and permit dynamic structural transformations in air- and moisture-sensitive suspensions of solids to be effectively studied.
32
Metzker, Julia Katheryn. "New methods of collection and interpretation in photoelectron spectroscopy: Applications to metallocenes." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279891.
Full textAbstract:
The use of ultraviolet photoelectron spectroscopy (UPS) to probe bonding and electronic structure in organometallic molecules is explored by development of new techniques for obtaining and interpreting valence ionizations in photoelectron spectra. Methods used in this work include understanding molecular functional group cross sections, determining communication between groups separated by alkane chains and the development of a new method of obtaining high quality UPS of surface-bound species. Our understanding of orbital mixing and the behavior of atomic orbitals in molecules is probed by investigation of a series of molecules containing functional groups separated by an alkane chain. The communication between functional endgroups is probed by varying the length of the alkane chain separating them. An investigation of these systems by variable photon energy photoelectron spectroscopy is presented and discussed. Molecules containing long (>10) alkane chains are described as models for gas-phase "solvation". Metallocene-terminated alkanethiol monolayers are prepared and analyzed as the first-ever method of obtaining high quality photoelectron spectroscopy organometallics in the condensed phase. The UPS of ferrocene and osmocene terminated monolayers are presented, showing that self-assembled monolayer technology can be successfully adapted to a method of producing UPS spectra of non-volatile molecules. Due to the unique environment of the metallocene, these terminated alkanethiol monolayers also act as an effective system to probe the effects of solvation on electronic structure and electron ionizations.
33
Darsey, Gary Paul. "The electronic structure of methyl-substituted ferrocenes and early transition metal bent metallocenes by gas phase ultraviolet and X-ray photoelectron spectroscopies." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184473.
Full textAbstract:
The details of the electronic structure and bonding in ferrocenes and early transition metal bent metallocenes are probed by photoelectron spectroscopy. The fundamental electronic interaction of the methyl group substituted for a hydrogen on a metal-coordinated cyclopentadienyl ring is shown by a combined core and valence pe spectroscopic study of a series of methyl-substituted ferrocenes. Shifts of core and valence ionization energies upon methyl substitution are equivalent and additive for the iron atom. Knowledge of the core ionization energy shifts for both carbon and iron allow the relative changes in atomic charges upon methyl substitution to be found. In these molecules, the methyl group is found not to be an inductive electron donor as is commonly assumed. The primary electronic effect of methyl substitution is on the valence orbitals of the cyclopentadienyl ring. Methylation of the cyclopentadienyl rings of ferrocene causes a dramatic redistribution of valence electron density and greatly increases the covalent nature of metal-ring bonding. An understanding of the electronic effect of methylation of metal-coordinated cyclopentadienyl rings is used to establish the relative locations of ring π and Cl ionizations in the pe spectra of group IV and V early transition metal bent metallocene dichlorides with both unsubstituted cyclopentadienyl and pentamethylcyclopentadienyl ligands. The differences in chloride and methyl ligand bonding to an early transition metal center are reflected in the photoelectron data of the dichlorides and related dimethyls. The relative differences in metal-chlorine and metal-carbon bond strengths are also shown in the pe data. The relationship between bond strengths and ionization energies is detailed for early transition metal bent metallocenes of niobium and tantalum with a variety of ligands. The relative bond strength/ionization energy information for metal-hydrogen and metal-carbon bonds is shown to help in understanding the stability of niobocene and tantalocene ethylene-hydride complexes and their resistance to intramolecular olefin insertion. Evidence from the pe data concerning the electron distribution as well as the relative bond strengths in these ethylene-hydride complexes is found supporting the consideration of these complexes more properly as metallacyclopropane-hydrides.
34
Taylor, Caroline Jean. "Novel synthetic methods for the formation of planar chiral iron and cobalt metallocenes." Thesis, Queen Mary, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428019.
Full text
35
Kheswa, Ntombizonke Yvonne. "Synthesis of the metallocenes for the production of exotic high energy ion beams." University of the Western Cape, 2019. http://hdl.handle.net/11394/6664.
Full textAbstract:
Philosophiae Doctor - PhDThe Subatomic Physics Department of iThemba Laboratory for Accelerated Based Sciences (iThemba LABS) conducts experiments that require a variety of particle beams in order to study nuclear properties (reaction, structure, etc.) of various nuclides. These particle beams are accelerated using the K-200 Separated Sector Cyclotron (SSC) and delivered to different physics experimental vaults. Prior to acceleration, the particle beam is first ionised using an Electron Resonance Ion Source (ECRIS). The main goal of this study is the production of exotic metallic beams of 60Ni8+ and 62Ni8+ using ECRIS4, which are required for the Coulomb excitation experiments approved by the Programme Advisory Committee (PAC) at iThemba LABS. In order to provide the metallic beams of nickel, a development study of organometallic materials containing 60Ni and 62Ni isotopes in a form of metallocene complexes was undertaken. The nickelocene (NiCp2) complex, a member of the organometallic family, was synthesised at the Physics Target Laboratory of iThemba LABS for the first time. Method development involved the use of natural nickel during the multi-step synthesis before the use of enriched nickel-60 (60Ni) and nickel-62 (62Ni). Nine samples of NiCp2 were synthesised; two were isotopically enriched nickelocene (60NiCp2 and 62NiCp2). The percentage yields of the synthesised nickelocene samples ranged between 16 to 50 %, and samples were characterised by investigating their crystal structure and bonding arrangements in the complexes by X-ray diffraction (XRD) , Fourier Transform Infrared (FT-IR) spectroscopy, and Proton Nuclear Magnetic Resonance (1H NMR). The synthesised nickelocene were further used with ECRIS4 for the production of Ni beams on the Q-line of the cyclotron. The Metal Ions from Volatile Compounds (MIVOC) technique was used for the conversion of 60Ni and 62Ni to ion species. The method used the organometallic compounds which are volatile at specific pressures at ambient temperatures. Metallic ion beams of nickel were successfully produced after a carefully pre-sample conditioning in the MIVOC container before connecting the MIVOC set-up to the new injection system of the ECRIS4. Measured beam intensities during the experiment for both 60Ni+ and 62Ni+ were approximately 30 μA, optimum for physics measurements. The development of the MIVOC technique opens up new beam-target combinations with the use of new exotic stable beams for new science cases at iThemba LABS. Reactions in inverse kinematics, multi-step Coulomb-excitation and other types of reactions will immensely benefit from these developments.
36
Geddes, Keira M. "The synthesis of novel planar chiral ansa-half-sandwich metallocenes containing a ferrocene linker." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415022.
Full text
37
Amin, Jahangir. "Efficient & novel approaches to relay chirality in the synthesis of planar chiral metallocenes." Thesis, University of East Anglia, 2010. https://ueaeprints.uea.ac.uk/47988/.
Full textAbstract:
Intermolecular and intramolecular dynamic kinetic resolution were detected for organocobalt complexed diynes prepared from the complexation of an alkyne to dicobalt hexacarbonyl, Co2(CO)6 and subsequent manipulation of the carbocationic charge generated at the carbon α– to the alkyne moiety via to the prior treatment with a Co2(CO)6– stabilised enyne, propargylic alcohol and alkynyl radical in a interesting departure from the Nicholas reaction. Diastereomeric ratios of up to 1:0 in favour of the anti diastereoisomer and yields of up to 67% were observed. Ether and ester linked diynes were synthesised from secondary terminal propargylic alcohols. On heating with (η5– cyclopentadienyl)bis(triphenylphosphine)cobalt(I), new chiral transition metal complexes were formed with high diastereomeric ratios in greater than 70% yield displaying in some cases four elements of chirality; central carbon chirality, chiral–at–metal chirality, conformational propeller phosphine chirality and conformational atropisomerism. Using mainly two representative examples the first a 7,5–membered cyclic lactone and the second a 5,5–membered cyclic ether complex the origins of chirality were explored which indicated the central carbon chirality relayed its stereochemical information to the stereogenic transition metal center thus resulting in a opposite configuration to the remote central carbon element of chirality i.e. (SC,RCo). Due to the unique properties of the 7,5–membered cyclic lactone complex a relatively stable major conformation propeller isomer of triphenylphosphine was found to be locked in space e.g. (SC,RCo,P). NMR analysis showed the presence of a dynamic equilibrium as three minor peaks of approximate equal intensity were observed which could be conformational atropisomers arising from hindered rotation between two interacting aromatics as a result of conformational flexibility inherent of the lactone architecture e.g. (P,aR), (R,aS), (M,aR), (M,aS). With respect to the 5,5–membered cyclic ether complex using a chiral ether diyne in a oxidative cyclisation reaction was found to result in chirality being relayed from the carbon stereogenic center to the chiral–at–metal stereocenter. As with the lactone complexes, an opposite configuration was observed. However, with respect to the conformation of triphenylphosphine it appeared to be non selective upon initial complexation. Recrystallisation gave an enriched (M) propeller conformational isomer which allowed the configurational stability of the chiral metal center to be measured which suggested that a mechanism did exist for epimerisation at metal but occurred only at an ambient temperature over several hours. Chiral metallocyclopentadiene complexes were treated with a selection of isocyanides and found to give novel planar chiral (η5–cyclopentadienyl)(η4–iminocyclopentadiene)cobalt metallocenes in good yields >60% yield and in some cases a diastereomeric ratio of up to 5:1. The isocyanide insertion reaction was in some cases complementary to the results observed for the isocyanides isoelectronic equivalent carbon monoxide which gave similar planar chiral (η5– cyclopentadienone)(η5–cyclopentadienyl)cobalt metallocenes. Preliminary results suggests because the isocyanide is smaller, in the diastereomeric transition state it is less discriminating compared to the chiral–at–metal complexes which are highly diastereoselective with respect to the configuration at metal. The methodology was extended to a non racemic example and found which gave a diastereomeric ratio of 2:1 and 92% yield.
38
Escribano, Sanvicente Alejandra [Verfasser], and Jürgen [Akademischer Betreuer] Heck. "1,2-Diarylethene Molecular Switches Connecting Cobalt and Iron Metallocenes / Alejandra Escribano Sanvicente. Betreuer: Jürgen Heck." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2015. http://d-nb.info/1074642406/34.
Full text
39
Bonnin, Quentin. "New cationic group 4 metallocenes as potential organometallic frustrated Lewis pairs : synthesis, reactivity and catalysis." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK031.
Full textAbstract:
Le concept de “paires frustrées de Lewis” (plus communément désignés par l’acronyme anglais FLPs) a suscité un vif intérêt depuis sa formulation en 2006. Initialement décrit à partir d’une phosphine encombrée comme base de Lewis et d’un borane comme acide de Lewis pour l’activation coopérative d’hydrogène sans métal, ce concept a été ensuite très largement développé en utilisant divers éléments du groupe principal (N/B, P/Al, N/Al …). Le concept a ensuite été étendu aux métaux de transitions pour pallier cette faiblesse: sont ainsi apparues les premières paires frustrées de Lewis organométalliques (OmFLPs). Dans le but de développer de telles OmFLPs, nous nous sommes intéressés à la synthèse de complexes cationiques titanocèniques et zirconocèniques en présence d’une amine. La première partie de cette thèse présente les travaux précédemment décrits sur les ligands azotés, en vue de synthétiser des complexes du groupe 4 N-fonctionnalisés. Une description plus détaillée du concept de FLP est ensuite réalisée, et un parallèle est fait avec des concepts connexes (coopérativité métal-ligand, systèmes ambiphiles). La seconde partie de ce manuscrit développe la synthèse de nouveaux ligands (aminomethyl)cyclopentadiènylure de potassium ainsi qu’une étude de leur coordination aux métaux du groupe 4. Cette étude a permis d’accéder à toute une série de nouveaux complexes dichlorotitanocènes et zirconocènes porteurs d’une fonction amine tertiaire encombrée (diisopropylaminyl et 2,2,6,6-tétraméthylpipéridine) à proximité du centre métallique. Ces travaux ont montré que l’amine ne se coordine pas audit centre métallique. Les métallocènes ainsi formés ont ensuite été transformés en cation afin de renforcer le caractère acidité de Lewis du centre métallique. Ces espèces ont montré une réactivité inattendue donnant lieu à des réarrangements par activation CH au voisinage de l’atome d’azote. Ces réarrangements ainsi que des études mécanistiques font l’objet du troisième chapitre. La quatrième partie de ce mémoire porte sur la synthèse de complexes phosphido- et amidotitanocènes cationiques. Ces complexes montrent une très bonne activité en catalyse d’hydrogénation de petites molécules dans des conditions relativement douces, vraisemblablement pour des raisons d’effets coopératifs entre le métal et le ligand. Dans une dernière partie, la synthèse de complexes titanocéniques cationiques portant une fonction iminophosphorane est développée, suivie d’une étude de réactivité de ces complexes en tant que paires frustrées de Lewis organométalliquesIn 2006, the concept of “frustrated Lewis pairs” (called FLPs) was introduced. The main characteristic of these compounds is their ability to activate cooperatively small molecules without the use of a metal (H2, CO2, alkene alkyne…). Initially based on P/B combination, the concept has been extended to several other main group elements (N/B, P/Al, N/Al …). Recently, FLPs have been extended to the transition metal realm. These organometallic FLPs (OmFLPs) are obviously non-metal free systems but they extend significantly the scope of FLP applications. Seeking to develop such systems, a research toward new omFLP combinations (N/Ti+, N/Zr+) has been initiated in our group, based on the synthesis of N-based titanocene and zirconocene complexes. The first part of this manuscript deals with a survey of the literature of such compounds, and a more detailed presentation of FLPs and related concepts (metal-ligand cooperativity, ambiphilic ligands) are also developed. In a second chapter, the synthesis of new N-based cyclopentadienyl ligands and their coordination to group 4 metals is presented. The formation of a cationic complex is then developed in a third part on selected titanocenes. In these complexes, the amine function undergoes CH activation by the cationic metal centre, leading to unexpected rearrangements. Investigations on their plausible mechanism are also presented. In a fourth part, the synthesis of new cationic phosphido- and amidotitanocenes, discovered in the course of our study on OmFLPs, is developed. The cationic amidotitanocenes are shown to be catalytically active towards hydrogenation of small molecules. Lastly, the potential of cationic titanocenyl iminophosphoranes as OmFLPs, was developed
40
Graef, Sven Markus. "Innovative spectroscopic and chromatographic techniques for the analysis of complex polyolefins prepared by metallocene catalysis." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52890.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2002.ENGLISH ABSTRACT: The study focused on the analysis of a variety o f synthesised tailored copolymers. During the investigation o f the samples new and innovative analytical techniques were developed to be able to identify the presence of certain predicted or expected copolymerisation products. Emphasis was placed on the versatility of CRYSTAF as a method for the analysis of semi-crystalline copolymers. Changes in the crystallisation temperature were used as an indicator, while the type o f method, solvent and sample weight served as variables in the system. The percentage comonomer content distribution for an unknown sample was determined from the standard curve plotted with the aid o f copolymers with known comonomer content. Ethylene/higher a-olefin and propylene/higher a-olefm copolymers were synthesised by means o f a metallocene precatalyst. In both cases, NMR spectroscopy, DSC, GPC, and CRYSTAF were used as analytical tools. In the ethylene series it was shown that the sample mixture was homogenous in the molar mass axis (GPC) but not in the chemical composition axis (CRYSTAF) regarding the comonomer content. For the propylene series, an increase in stereoerrors was observed by NMR and this was correlated with crystallisation on heating a DSC for the range o f copolymers. In the case where ethylene/methyl methacrylate block copolymers were synthesised using metallocene precatalyst, novel detection and separation methods were used and developed. This included the use o f CRYSTAF fitted with a carbonyl filter, high temperature gradient HPLC and high temperature liquid chromatography under critical conditions (LCCC). The last two techniques were the first where separation could be achieved with samples only dissolving at high temperature. All previous mentioned techniques, as well as the coupling of FTIR to GPC and high temperature gradient HPLC via LC-Transform revealed that the samples consisted o f varying ethylene and MMA block lengths.
AFRIKAANSE OPSOMMING: Die doelstelling van die navorsing was die analise van spesiaalvervaardigde kopolimere. Nuwe analitiese tegnieke is vir die bevestiging van sekere voorgestelde kopolimerisasie-produkte ontwikkel. Klem is gelê op die veelsydigheid van CRYSTAF as ’n metode vir die analise van gedeeltelik-kristallyne kopolimere. Veranderinge in die kristallisasie-temperature is as respons gebruik, terwyl die metode van sintese, die oplosmiddel en die hoeveelheid monster as veranderlikes in die sisteem beskou is. ‘n Standaardkurwe vir komonomeerinhoud is opgestel met behulp van kopolimere met ‘n bekende komonomeerinhoud. Hierdie kurwe is gebruik om die komonomeerinhoudsverspreiding van onbekende monsters te bepaal. Etileen/hoër a-olefien- en propileen/hoër a-olefien-kopolimere is met behulp van ‘n metalloseen pre-katalis gesintetiseer. In beide gevalle is KMR spektroskopie, DSC, GPC en CRYSTAF gebruik om die analises uit te uitvoer. Met verwysing na komonomeerinhoud is daar in die geval van die etileenreeks bevind dat die monstermengsel homogeen is met betrekking tot die molere massa, maar nie met betrekking tot die chemiese samestelling nie. Vir die propileenreeks is ’n verhoging in die stereofoute met behulp van KMR waargeneem. Dit is gekorrelleer met kristallisasie weens verhitting tydens DSC-bepalings vir die reeks kopolimere. In die geval van die sinteses van etileen/metielmetakrilaat-blokkopolimere met metalloseen as pre-katalis, moes nuwe waamemings- en skeidingstegnieke ontwikkel word. Dit het die gebruik van CRYSTAF met ’n karbonielfilter, hoetemperatuurgradient- HPLC en hoë-temperatuurvloeistofchromatografie onder kritiese toestande ingesluit. Laasgenoemde twee tegnieke het vir die eerste keer skeiding van monsters wat net by hoe temperature oplos, moontlik gemaak. Bogenoemde tegnieke, sowel as die koppeling van FTIR met GPC en hoë-temperatuur-gradient-HPLC via LC-transformasie het getoon dat die monsters etileen- en MMA-blokke met verskillende lengtes bevat het.
41
Bashir, Muhammad Ahsan. "Impact of Physical Properties of Silica on the Reaction Kinetics of Silica Supported Metallocenes and Polyethylene Morphology." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1253/document.
Full textAbstract:
Les polyolefins représentent plus de la moitié de la production mondiale de plastiques et 80% de ces polymères sont produits avec des catalyseurs hétérogènes de type Phillips, Ziegler-Natta et métallocènes. En effet, un bon fonctionnement des unités du fait d'un faible encrassement du réacteur ou des autres équipements de l'unité, une activité stable, une bonne morphologie particulaire des polymères et un une densité apparente élevée sont obtenus en utilisant des catalyseurs hétérogènes. D'un autre côté l'hétérogénéisation d'un catalyseur s'accompagne d'une diminution de l'activité et d'un élargissement de la distribution de masses molaires qui est parfois non désiré car cela peut influencer l'aptitude à la transformation et les propriétés mécaniques des polyoléfines. Plusieurs explications ont été avancées dans la littérature afin d'expliquer l'effet de l'immobilisation d'un catalyseur ce qui inclut la résistance diffusionnelle au transport du (des) (co)- monomère(s) vers le site actif et la modification du comportement du catalyseur conduisant à plusieurs espèces actives. Néanmoins l'ensemble de ces explications est en connexion avec les propriétés physiques du support (tailles des particules, surface spécifique, volume poreux, diamètre des pores…) car ce dernier peut en effet impacter la nature des espèces actives ainsi que leur dispersion et la diffusion des monomères. Les catalyseurs métallocène sont considérés comme mono-site et tout changement dans la nature du site actif au cours de son immobilisation et toute résistance au transfert de matière peuvent être détectés par un élargissement de la distribution des masses molaires. Le présent travail a pour objet d'étudier les effets des propriétés physiques des catalyseurs métallocènes supportés sur silice concernant la cinétique de polymérisation et les caractéristiques des polymères produits. Pour cela le traitement thermique de la silice a été fixé à 600°C afin de contrôler son état de surface tandis que la quantité de catalyseur supporté a été gardée autant que possible constante. De plus les protocoles de polymérisation en phases suspension et gaz ont été fixés après avoir évalué différentes conditions de polymérisation et différents composés alkylaluminium. Cette étude systématique a permis d'attribuer les différences observées en termes de cinétique de réaction des catalyseurs métallocènes à la différence des paramètres physiques des silices utilisées comme support et par conséquent à la résistance diffusionnelle au transport du (des) (co)-monomère(s) au(x) site(s) actif(s) durant la polymérisationPolyolefins account for more than half of the world’s plastic production and about 80% of these polyolefins are commercially produced with heterogeneous olefin polymerization catalysts such as Phillips, Ziegler-Natta and metallocenes. Trouble-free plant operation due to low fouling of the reactor or other plant equipment, relatively stable catalytic activity, good polymer morphology and high polymer bulk densities can be achieved by employing heterogeneous olefin polymerization catalysts. On the other hand, heterogenization of the olefin polymerization catalysts lead to drastic reduction in their activities and broadening of the polymer molar mass distribution which is undesirable in some cases because it can influence the processability and mechanical properties of the polyolefin grade. Various explanations have been proposed in the open literature to explain these effects of catalyst immobilization which mainly include existence of diffusion resistance to (co)-monomer(s) transport at the active sites during polymerization and the change of the active site(s) behavior due to immobilization leading to multiple site types on the final supported catalyst. Nevertheless, both of these explanations have a connection with the physical properties (e.g., particle size, surface area, pore volume, pore diameter etc.) of the support because the support can impact the nature of the final active species formed on it, dispersion of the active species throughout the support particles and, last but not the least, the intraparticle diffusion of (co)-monomer(s) during polymerization. Metallocenes are considered as single-site catalysts and any changes in the nature of the active site(s) upon their immobilization on a support or during the course of polymerization due to mass transfer resistance can be detected from the broadening of polyolefin molar mass distribution. Therefore, the present work is an attempt to study the effects of physical properties of silica supported metallocenes on their ethylene polymerization kinetics as well as on the morphology of the produced polyethylene. For this purpose, the surface chemistry of the used commercial silica supports was fixed by dehyroxylating all of them at 600 °C, whereas, the final metal loadings of the supported catalysts were nearly kept constant by preparing them under identical conditions. Furthermore, slurry and gas phase polymerization protocols along with the used aluminum alkyl scavenger (which can also induce chemical effects on the catalytic behavior of supported metallocenes) were also fixed by testing different polymerization protocols and scavengers. Such systematic study has allowed us to attribute the observed differences in the reaction kinetics of the supported metallocenes, explicitly, to the differences in the physical parameters of the silica supports and, consequently, to the existence of diffusion resistance to (co) monomer(s) transport at the active site(s) during the course of polymerization
42
Conway, Stephen L. J. "Structure reactivity relationships in metallocene chemistry : the ansa-effect." Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:3a155469-19c6-4fbc-b77a-d24f8b27456e.
Full textAbstract:
This thesis is concerned with structure-reactivity relationships in metallocene chemistry. In particular new ansa-metallocenes of Groups 5-7 have been prepared. The structure and reactivity of these ansa-metallocenes is compared to the corresponding nonbridged metallocenes.
43
Bouvet, Carola. "Chirale und redoxaktive (Raumtemperatur-)Ionische Flüssigkeiten basierend auf Ferrocen und S-Prolin." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-211680.
Full textAbstract:
In der vorliegenden Dissertation geht es um die Synthese und Charakterisierung chiraler, redoxaktiver (Raumtemperatur-)Ionischer Flüssigkeiten basierend auf Ferrocen und der natürlich vorkommenden Aminosäure S-Prolin. Diese Baueinheiten sind entweder über eine Ether- oder über eine Esterverbrückung verknüpft. Auch der Anionenaustausch vom I– - zum CF3SO3– - sowie (CF3SO2)2N– -Salz (kurz NTf2–) wird dargelegt und der Einfluss des Anions auf den Schmelzpunkt der Verbindungen untersucht und diskutiert. Die Redoxaktivität wird durch das im Ferrocen enthaltene Fe II eingebracht, das reversibel zu Fe III oxidiert werden kann. Aufgrund des Pyrrolidin-Rings sind die dargestellten Verbindungen stets chiral und bilden nach der Quaternisierung mit Halogenalkanen Diastereomere, soweit die Alkylkette größer als Methyl ist. Das Diastereomerenverhältnis wurde mittels 1H-NMR-Spektroskopie und in einem Fall anhand von Röntgenpulverdiffraktogrammen durch Rietveld-Verfeinerung analysiert. Die Verbindungen wurden thermisch anhand simultaner thermischer Analysenund Tieftemperaturversuchen untersucht, die belegen, dass die Synthese von insgesamt sechs neuen Raumtemperatur-Ionischen Flüssigkeiten gelang. Davon basiert eine Verbindung, (1S2S)- und (1R2S)-2-[(Ferrocenylcarbonyl)oxy]methylen-N-methyl-N-pentylpyrrolidin-1-iumiodid, auf I– und fünf Verbindungen enthalten NTf2– als Gegenion. Das Diastereomerengemisch der Verbindungen (1S2S)- und (1R2S)-N-Butyl-2-[(ferrocenylcarbonyl)oxy]methylen-N-methylpyrrolidin-1-ium NTf2– besitzt den größten Flüssigkeitsbereich von -25 bis +263 °C und auch die höchste Zersetzungstemperatur aller hier dargestellten Verbindungen. Insgesamt werden in dieser Arbeit elf Einkristallstrukturanalysen vorgestellt, wobei es sich um drei Verbindungen des Typs FcCH2N(CH3)2(CnH2n+1)I (Fc = Ferrocenyl, n = 1,2,3), Ferrocenmonocarbonsäurechlorid, zwei ether- sowie fünf esterverbrückte Verbindungen handelt. Mikrokristalline Proben wurden mittels Röntgenpulverdiffraktometrie charakterisiert. Ergänzende Analysen wurden mittels UV-Vis- und IR-Spektroskopie sowie Massenspektrometrie und Elementaranalyse durchgeführt. Ein wichtiger Aspekt bei Ferrocenverbindungen ist das Redoxpotential, welches mittels Cyclovoltammetrie bestimmt wurde. Hierbei liegt das Formalpotential des Fe II /Fe III -Redoxpaars der etherverbrückten Verbindungen bei +0,05 V und bei den esterverbrückten Verbindungen unabhängig vom Anion bei +0,28 V vs. Ferrocen/Ferrocenium in Acetonitril. Bei den iodidhaltigen Verbindungen zeigt das I– -Ion ebenfalls eine Redoxaktivität bei E(0,f,Fc) = -0,18 V und 0,22V. Die Diffusionskoeffizienten der esterverbrückten Triflat- und NTf2– -Verbindungen liegen in der Größenordnung von 7·10−6 cm2/s und die heterogenen Geschwindigkeitskonstanten bei 0,01 cm/sThe present dissertation deals with the synthesis and characterization of chiral, redoxactive room temperature ionic liquids (RTILs) based on ferrocene and the naturally occurring amino acid S-proline. These building blocks are coupled either via an ether- or an ester-bridge. The anion exchange from I– to CF3SO3– and (CF3SO2)2N– salts (abbreviated as NTf2–) is presented. The influence of the anion on the melting point of the compound is investigated and discussed. The redox activity is introduced into the molecule via the Fe II -containing ferrocenyl groups, which can be oxidized reversibly to Fe III . The synthesized compounds based on the pyrrolidine ring are chiral. After quaternization with alkyl halides, they form diastereomers in case of alkyl chains longer than methyl. The ratio of the different diastereomers was analyzed by 1H NMR spectroscopy and, in one case, by Rietveld refinement of the X-ray powder diffraction pattern. The thermal behavior of the compounds was studied by simultaneous thermal analysis and low temperature experiments. The results show the successful synthesis of six new RTILs. One of them is based on iodide ((1S2S)- and (1R2S)-2-[(ferrocenylcarbonyl)oxy]methylene-N-methyl- N-pentylpyrrolidine-1-ium iodide) and six RTILs contain NTf2– as counter ion. The diastereomeric mixture of compounds (1S2S)- and (1R2S)-N-butyl-2-[(ferrocenylcarbonyl)oxy]methylene-N-methylpyrrolidine-1-ium NTf2– exhibits the widest liquid range from -25 to +263 °C and the highest decomposition temperature of all compounds presented herein. Eleven single crystal structure analyses are presented. Three of them belong to compounds FcCH2N(CH3)2(CnH2n+1)I (with Fc = ferrocenyl and n = 1,2,3), then ferrocene monocarboxylic acid chloride, two of ether- as well as five ester-bridged compounds. Microcrystalline samples were characterized by X-ray powder diffractometry. Supplementary analyses by UV/Vis and IR spectroscopy as well as mass spectrometry and elemental analyses have been carried out. An important feature of ferrocene containing compounds is their redox potential which is determined with cyclic voltammetry. The formal potential of the Fe II /Fe III redox couple in the ether-bridged compounds is at +0.05 V and in the ester-bridged compounds independent from the type of anion at +0.28 V vs. ferro- cene/ferrocenium in acetonitrile. The I– anion shows as well redox activity with formal potentials at E(0,f,Fc) = -0.18 V and 0.22 V. The diffusion coefficients of the ester-bridged triflate and NTf2– compounds are in the order of 7·10−6 cm2/s, the heterogeneous rate constants in the order of 0.01 cm/s
44
Rapakousiou, Amalia. "Ingéniérie des nanomatériaux redox métallocèniques." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0437/document.
Full textAbstract:
Les dendrimères et polymères contenant des métaux de transition comme le fer, lecobalt et le rhodium peuvent servir à la fabrication des nanomatériaux utiles à lacatalyse, la reconnaissance moléculaire et l’électronique moléculaire. Pour leurconstruction, des liaisons ioniques, de la chimie click : CuAAC et hydroamination, lapolymérisation ROMP et la polymérisation radicalaire ont été utilisés et ont permis laformation de nouveaux types de polyélectrolytes metallocéniques. La synthèse denouvelles nanoparticules d’or, d’argent et de palladium à partir de cesmétallopolymères et métallodendrimères ont été mises au point, conduisant à desréseaux à architecture spécifique bien définie. Ces assemblages supramoléculaireset ingénierie moléculaire ouvrent la voie vers l’application de la chimieorganométallique dans la conception de nouveaux nanomatériaux nanoparticulairesstructurés à l’aide des propriétés rédox des métallomacromoléculesDendrimers and polymers containing transition metals such as iron, cobalt andrhodium can serve in the fabrication of useful nanomaterials for catalysis, molecularrecognition and molecular electronics. For their construction, ionic bonds, clickchemistry: CuAAC and hydroamination, ROMP and radical polymerization were usedand allowed the formation of new types of metallocenyl polyélectrolytes. Thesynthesis of new gold, silver and palladium nanoparticles from these metallopolymersand metallodendrimers has been developed, leading to specific and well-definedarchitectures. These supramolecular assemblies and molecular engineering opensthe way towards the application of organometallic chemistry in the design of newstructured nanoparticle-containing nanomaterials using the redox properties ofmetallomacromolecules
45
Laur, Eva. "Rare-earth metallocene complexes for syndioselective styrene (co)polymerization." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S168.
Full textAbstract:
Les travaux présentés dans ce manuscrit portent sur la (co)polymérisation syndiosélective du styrène catalysée par des complexes de métaux du Groupe 3. La première partie est consacrée à l’optimisation des performances catalytiques de systèmes neutres de type {Cp/Flu}. Une série de précurseurs ansa-lanthanidocènes a été synthétisée et testée en homopolymérisation du styrène et en copolymérisation styrène-éthylène. Il a été montré que la nature de la substitution du motif fluorényle, la nature du centre métallique ainsi que les conditions de polymérisation ont une influence significative sur la productivité des catalyseurs. En conditions optimisées, des productivités maximales de 4,500 kg(sPS)·mol⁻¹·h⁻¹ et 5,430 kg(sPSE)·mol⁻¹·h⁻¹ ont été obtenues, démontrant la robustesse sans précédent de ces systèmes catalytiques en conditions extrêmes (Tpolym jusqu’à 140 °C et charge en monomère > 100,000). De nouveaux co- et terpolymères styrène-myrcène et styrène-myrcène-éthylène contenant des séquences de polystyrène syndiotactique ont également été synthétisés. La deuxième partie de ce travail porte sur le développement de nouveaux catalyseurs cationiques. Très peu des composés ciblés ont été isolés de par la réactivité déroutante entre les pro-ligands et les précurseurs ou la faible stabilité thermodynamique des produits. De plus, les productivités catalytiques des composés qui ont été isolés se sont avérées assez faiblesThe work presented in this thesis manuscript focuses on the syndioselective (co)polymerization of styrene catalyzed by Group 3 catalysts. The first part is dedicated to the optimization of the catalytic performances of neutral {Cp/Flu} systems. A series of new allyl ansa-lanthanidocenes was synthesized and explored in styrene and styrene-ethylene (co)polymerizations. It is shown that the substitution of the fluorenyl moiety as well as the nature of the metal center and the polymerization conditions exert a strong influence on the catalyst productivity. Under optimized conditions, maximum productivities of up to 4,500 kg(sPS)·mol⁻¹·h⁻¹ and 5,430 kg(sPSE)·mol⁻¹·h⁻¹ were achieved, highlighting the unprecedented robustness of those catalytic systems under drastic conditions (Tpolym up to 140 °C and monomer : catalyst ratios > 100,000). New styrene-myrcene(-ethylene) co- and terpolymers containing syndiotactic polystyrene sequences were also synthesized. The second part of the study was focused on the development of new cationic catalysts. Only a short series of compounds was successfully isolated among the targeted ones, because of unclear reactivity of pro-ligands and metal precursors and/or low thermodynamic stability of the products. The new isolated compounds were also used in styrene homopolymerization affording unexpectedly poor performances
46
Tatistcheff, Helen B. "Use of microelectrochemical devices to study diffusion of electroactive species in nonfluid media and photoelectrochemistry of surface-confined metallocenes." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17373.
Full text
47
Loukova, G. V. "Harvesting and Electron-Exchange Energy Transfer by d0 Metallocene-based Organized Systems." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35397.
Full textAbstract:
The present contribution will provide an up-to-date overview of novel experimental and theoretical (de-rived quantum-chemically) knowledge on photonics of group IV metallocene-based systems, also with re-spect to their prominent use in catalysis and photoluminescent sensor activity. We have developed photo-physical approach to study measurable properties of the frontier MOs of the complexes, estimate orbital nature of rare long-lived ligand-to-metal charge transfer (LMCT) excited states and also supramolecular interactions between basic components of catalytic systems for polymerization: d0-metal complexes and un-saturated hydrocarbon substrates in fluid systems. In the similar way, the photophysical approach is high-lighted to enable studying fine intermolecular interactions in homogeneous systems with low (catalytic) concentrations of metal complexes that cannot be achieved by other conventional methods.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35397
48
Hicks, Jason Christopher. "Organic/inorganic hybrid amine and sulfonic acid tethered silica materials synthesis, characterization and application /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26583.
Full textAbstract:
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Jones, Christopher; Committee Member: Koros, William; Committee Member: Lyon, Andrew; Committee Member: Nair, Sankar; Committee Member: Weck, Marcus. Part of the SMARTech Electronic Thesis and Dissertation Collection.
49
Rowland, Tyson G. "Accurate ionic bond energy measurements with TCID mass spectrometry and imaging PEPICO spectroscopy." Scholarly Commons, 2012. https://scholarlycommons.pacific.edu/uop_etds/809.
Full textAbstract:
Two projects are presented here. In the first, metal-cyclopentadienyl bond dissociation energies (BDEs) were measured for seven metallocene ions (Cp2M+, Cp = η5-cyclopentadienyl = c-C5H5, M = Ti, V, Cr, Mn, Fe, Co, Ni) using threshold collision-induced dissociation (TCID) performed in a guided ion beam tandem mass spectrometer. For all seven room temperature metallocene ions, the dominant dissociation pathway was simple Cp loss from the metal. Traces of other fragment ions were also detected, such as C10H10+, C10H8+, C8H8+, C3H3+, H2M+, C3H3M+, C6H6M+, and C7H6M+, depending on the metal center. Statistical modeling of the Cp-loss TCID experimental data, including consideration of energy distributions, multiple collisions, and kinetic shifts, allow the extraction of 0 K [CpM+ - Cp] BDEs. These are found to be 4.95 ± 0.15, 4.02 ± 0.14, 4.22 ± 0.13, 3.51 ± 0.12, 4.26 ± 0.15, 4.57 ± 0.15, and 3.37 ± 0.12 eV for Cp2To+, Cp2V+, Cp2Cr+, Cp2Mn+, Cp2Fe+, Cp2Co+, and Cp2Ni+, respectively. The measured BDE trend is largely in line with arguments based on a simple molecular orbital picture, with the exceptions of a reversal in Cp2Mn+ and Cp2Ni+ BDEs (although within uncertainty), and the exceptional case of titanocene, most likely attributable to its bent structure. The new results presented here are compared to previous literature values and are found to provide a more complete and accurate set of thermochemical parameters.
In the second project, imaging photoelectron photoion coincidence (iPEPICO) spectroscopy has been used to determine 0 K appearance energies for the unimolecular dissociation reactions of several energy selected 1-alkyl iodide cations n-CnH2n+1I+ → CnH2n+1+ + I, (n = 2-5). The 0 K appearance energies of the iodine-loss fragment ions were determined to be 9.836 ± 0.010, 9.752 ± 0.010, 9.721 ± 0.010, and 9.684 ± 0.010 eV for n-C3H7I, n-C4H9I, n-C5H11I, and n-C6H13I molecules, respectively. Isomerization of then-alkyl iodide structures into 2-iodo species adds complexity to this study. Using literature adiabatic ionization energies, ionic bond dissociation energies were calculated for the four modeled iodoalkyl cations and it was shown that as the alkyl chain length increases, the carbon-halogen bond strength decreases, supporting the suggestions set forth by inductive effects. In the modeling with statistical energy distributions and rate theory, the role of hindered rotors was also evaluated and no strong experimental evidence was found either way. The heaviest species in the series, heptyl iodide (C7H15I) was also measured via iPEPICO and showed to have a greater complexity of fragmentation than the lighter analogs. Sequential dissociation of the first fragment ion, C7H15+ leads to C4H9+, C5H11+, and C3H7+ ions in competitive dissociation processes, dominated at low energies by the C4H9+ cation.
50
Johannsen, Matthias. "Metallocen-katalysierte Synthese von polaren Olefin-basierten Makromonomeren." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-84573.
Full textAbstract:
1 Ziel und Gegenstand der Untersuchungen
Gegenstand der vorliegenden Arbeit war die Synthese und Charakterisierung von polaren Olefin-basierten Makromonomeren mit Hilfe von Metallocen-Katalysatoren.
Polyolefine stellen eine Gruppe von Polymeren dar, die durch Additive oder chemische Veränderungen modifiziert, eine große Vielfalt von Einsatzmöglichkeiten auf der Basis einfach aufgebauter Monomere bieten. Sie stellen deshalb heutzutage die wichtigste Kunststoffgruppe dar. Ein Nachteil ist jedoch die unpolare Struktur dieser Polymere.
Ziel dieser Arbeit war die Homopolymerisation polarer Olefine, um ein funktionalisiertes Polyolefin zu erzeugen, dass zudem auch als Makromonomer einsetzbar ist.
Als Katalysatoren wurden im Wesentlichen die klassischen Metallocene auf Zr-Basis eingesetzt, aktiviert mit MAO. Die Makromonomere wurden im Anschluss an die Synthese umfassend charakterisiert.
2 Ergebnisse
Zur Synthese wurde das bekannte 10-Undecen-1-ol (Undecenol) eingesetzt. Für eine erfolgreiche Homopolymerisation dieses Monomers ist eine effektive Abschirmung des Katalysators gegenüber der polaren Gruppe zur Minimierung der Deaktivierung des Katalysators zu gewährleisten. Für die Einführung von Schutzgruppen fand Triisobutylaluminium (TIBA) Verwendung. Auf diese Weise konnte erstmalig erfolgreich die Synthese von Polyundecenol mit Metallocen-Katalysatoren durchgeführt werden.
Es zeigte sich, dass Undecenol als polares und zugleich sterisch anspruchsvolles Monomer mit der überwiegenden Anzahl der eingesetzten Metallocene schwierig zu polymerisieren ist, was im Vergleich zur Polymerisation von kurzkettigen 1 Olefinen, wie zum Beispiel Propen, anhand von geringen Molmassen (< 2000 g/mol) aber auch geringen Ausbeuten zum Ausdruck kommt. Die erzielten Molmassen der Polyundecenole sind jedoch für die Verwendung als Makromonomer vorteilhaft.
Die höchsten Polymerausbeuten ermöglichte der Einsatz von ansa-Metallocenen. Mit dem Katalysator Et[Ind]2ZrCl2 konnten hierbei relative Ausbeuten im Bereich von 50 % bis 60 % bei gleichzeitig geeigneten Molmassen von < 10^4 g/mol erzielt werden. Bei der Verwendung von unverbrückten Metallocenen (bis-Cyclopentadienylkomplexe) sind die Ausbeuten und Molmassen im Vergleich zu den ansa-Metallocenen deutlich reduziert.
Die synthetisierten Polyundecenole wurden hinsichtlich ihres Schmelz- und Kristallisationsverhaltens sowie der kristallinen Struktur untersucht und der Zusammenhang mit der Taktizität und der Molmasse der Polymere hergestellt. Die Ergebnisse der DSC und WAXS Untersuchungen lassen darauf schließen, dass für ataktische und isotaktische Polyundecenole eine Seitenkettenkristallisation als primäre Form der Kristallisation vorliegt. Aufgrund des hohen Gehalts von Hydroxylgruppen, die durch Wasserstoffbrückenbindungen wechselwirken, weist Polyundecenol hohe Schmelztemperaturen auf, im Vergleich mit dem unpolaren Poly(1-Undecen). So besitzt isotaktisches und auch ataktisches Polyundecenol bei vergleichbaren Molmassen eine um rund 80 K höhere Schmelztemperatur als Poly(1-Undecen). Die Wechselwirkung der Hydroxylgruppen wurde mittels FTIR-Spektroskopie nachgewiesen und liegt auch im geschmolzenen Zustand der Polymere vor.
Anhand der Ergebnisse von WAXS-Untersuchungen konnte gezeigt werden, dass Polyundecenol in smektischen Schichten kristallisiert. Der Abstand zwischen den Hauptketten entspricht etwa zwei vollständig gestreckten Seitenketten des Polymers, welche orthogonal zur Hauptkette angeordnet sind. Diese Schicht-Anordnung wurde unabhängig von Molmasse und Taktizität der Polymere nachgewiesen und lässt die Schlussfolgerung zu, dass die Kristallisation isotaktischer Rückgrat-Ketten gegenüber der Seitenketten-Kristallisation unterdrückt ist. Es wurde jedoch beobachtet, dass die Taktizität einen Einfluss auf die Kristallisation hat. Polyundecenole mit isotaktischer Hauptkette weisen bei entsprechend langsamer Kristallisation eine Anordnung der Seitenketten in einer monoklinen Packung auf, was als Hinweis auf eine Kristallisation der Hauptkette interpretiert wird, auch wenn diese im Rahmen der Arbeit nicht eindeutig nachgewiesen werden konnte.
Bei Polyundecenolen mit ataktischer Hauptkette ordnen sich die Seitenketten hingegen in einer hexagonalen Packung an, da die Hauptkette nicht in der Lage ist zu kristallisieren.
Von besonderer Bedeutung für die Synthese der Polyundecenole waren einerseits die erzielbaren Polymerausbeuten, andererseits aber auch die Einführung geeigneter Endgruppen, welche ausschlaggebend sind für eine Nutzung als Makromonomer.
Die Untersuchungen zum Polymerisationsverhalten verschiedener Metallocen-Katalysatoren zeigten, dass im Falle von ansa-Metallocenen sowie einem "CGC"-Komplex Polymere erhalten werden, die vor allem Endgruppen mit internen Doppelbindungen, doppelt- und dreifachsubstituiert, aufweisen. Solche Endgruppen sind jedoch für einen späteren Einsatz der Polymere als Makromonomer ungeeignet. Der Einsatz von unverbrückten Metallocen-Katalysatoren auf Basis der Biscyclopentadienyl-Struktur ermöglicht hingegen die Synthese von Polyundecenol mit einem hohen Anteil endständiger Vinyliden-Endgruppen zu synthetisieren. Die so erreichten Vinyliden-Endgruppenanteile bewegten sich nahezu unabhängig vom Katalysator im Bereich von etwa 85 % bis 90 %.
Ein wesentliches Ergebnis der Arbeit stellt die Synthese von Polyundecenol mit Allyl-Endgruppen dar. Dieses wurde durch gezielte Kettenabbruchreaktionen mit Hilfe von Vinylchlorid erreicht. Bei Einsatz des Katalysator MBI konnten Anteile der favorisierten Allyl-Endgruppe von rund 90 % erreicht werden. Somit wurden auf diesem Wege erstmalig erfolgreich Polyundecenol-Makromonomere synthetisiert. Ein Einsatz dieser Polymere in der Copolymerisation mit Propen wurde aber durch geringe Ausbeuten verhindert. Jedoch konnte gezeigt werden, dass der Einsatz von Vinylchlorid die Synthese von Polyundecenol-Makromonomeren ermöglicht.