Thesis (Ph.D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 197-212) Also available in print.

Thesis (M.Sc.)--York University, 2006. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references. Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR29571

This study investigated the reduction reaction of ruthenium tetroxide by various aliphatic alcohols in acidic medium. UV-Vis spectroscopy still plays an essential role in the analysis and study of volatile ruthenium tetroxide and was used in this study to collect kinetic data. This data was analyzed using graphical and computational methods, such as Mauser diagrams and kinetic simulation software. From the results obtained it is proposed that the reaction occurs by the following two-step reaction model: Ru(VIII) k1 Ru(VI) Ru(VI) k2 k-2 Ru(III) Molar extinction coefficients and conditional rate constants were calculated using kinetic simulating software and a hydride transfer mechanism was proposed. The temperature dependence of this reduction reaction was also investigated and thermodynamic parameters calculated. Ruthenium concentrations were determined using a method employing UV-Vis spectroscopy. The method proved to be a reliable, sensitive and simple technique.

The previously reported synthesis of dinuclear mixed-valence ruthenium complexes of general formula Ru₂Cl₅(P-P)₂, P-P = DPPP, DPPB, 5,5-CHIRAPHOS, or R.R-DIOP, has been extended to include other diphosphines: P-P = DPPN, DPPH, rac-DPPCP, rac-DPCYCP, S,S-BDPP, R- and S-BINAP, or S-PHENOP. The complexes are prepared by the reaction of RuCl₃P₂(DMA)-DMA, P = PPh₃ or P(p-tolyl)₃, with one equivalent of the appropriate diphosphine. The H₂-reduction of Ru₂Cl₅(P-P)₂ complexes in DMA, or in toluene in the presence of an added base, affords the corresponding dimeric Ru(II) complexes [RuCl(P-P)(µ-Cl)]₂, P-P = DPPN, R- or S-BINAP, or S,S-BDPP, which have been characterised by NMR spectroscopy. The [RuCl(P-P)(µ,-Cl)]₂ complexes (Structure I) show a great propensity to form trichloro-bridged dinuclear species (Structure II) in the presence of neutral coordinating ligands (L). A series of trichloro-bridged complexes of the type [(L)(P-P)Ru-(µ-Cl)₃RuCl(P-P)] (e.g. P-P = DPPB; L = NEt₃, NHBu₂, CO, DMA, PhCN, Mel) have been isolated or studied in situ and characterised spectroscopically. The molecular structure of the DMSO analogue shows an S-bonded DMSO ligand with an unsymmetrical arrangement of the chelating DPPB ligand (cf. Structure II). [ Formulas omitted ] The reaction of [RuCl(DPPB)(µ,-Cl)]₂ with H₂ has been investigated. In benzene or toluene, in the absence of an added base, dihydrogen adds reversibly to the ruthenium dimer to give the remarkably simple molecular hydrogen complex (L = η²-H₂; Structure II); the η²-H₂ ligand (with an H-H distance of 0.86 Å as estimated by ¹H NMR variable temperature spin-lattice relaxation data; T₁(min) - 12 ms at 300 MHz) is replaceable by N2. The reaction of [RuCl(P-P)(µ-Cl)]₂, P-P = DPPB or 5,5-CHIRAPHOS, with H₂ in the presence of NEt₃ as the added base yields the corresponding trinuclear Ru(II) hydride complex, [RuHCl(P-P)]₃, along with [(NEt₃)(P-P)Ru(u-Cl)3RuCl(P-P)]. The hydride complexes had been synthesised previously, albeit in low yields (<10%), and the crystal structure of the CHIRAPHOS derivative obtained. During the present work the original synthetic procedure has been modified to obtain the desired [RuHCl(P-P)]₃ complexes in ∼50% yield. In addition, these species have been characterised completely by NMR spectroscopy. The conversion of [RuCl(P-P)-((µ-Cl)]₂ to the corresponding hydride derivative likely proceeds via deprotonation by NEt₃ of the initially formed molecular hydrogen species. Under hydrogen atmosphere, [RuHClQDPPB)]₃ breaks down to form the dinuclear derivative [(η²-H₂)(DPPB)Ru(µ-H)(µ-Cl)₂RuH(DPPB)] containing a molecular hydrogen ligand, which has been identified by ¹H NMR T₁ measurements; similar complexes, but with a nitrile ligand (MeCN or PhCN) in place of the η²-H₂, have also been observed. Alternative routes to ruthenium complexes containing only one diphosphine per Ru ("RuII(P-P)") have been investigated. Some of the trichloro-bridged derivatives (e.g. L = amine, CO; Structure II, see above) are also accessible through reactions of the mixed-phosphine complex RuCl₂(DPPB)(PPh₃) with amines and aldehydes, respectively. Studies on the reactions of RuCl₂(DMSO)₄ or [RuCl(p-cymene)-(µ,-Cl)]₂ with one equivalent of diphosphines show that the nature and the distribution of product(s) (i.e. RuCl₂(P-P)₂ vs. "RuCl₂(P-P)") are greatly influenced by the chelate size of the diphosphine. The "RuCl₂(P-P)" species is observed only for those phosphines which form at least a six-membered ring upon coordination to the metal. Solid-state ³¹P NMR studies indicate that the structure of RuCl₂(DPPB)(PPh₃) is similar to that of RuCl₂(PPh₃)₃, which has been characterised previously by X-ray crystallography. Reactions of RuCl₂(DPPB)(PPh₃) with chelating ligands afford six-coordinate complexes of the type RuCl₂(DPPB)(L-L), L-L = PPh₂Py, DPPM, or norbornadiene; the corresponding hydridochloro derivatives are obtained when the reactions are conducted under an atmosphere of H₂ in the presence of Proton Sponge®. The dimeric [RuCl(P-P)(µ-Cl)]₂ and the trinuclear [RuHCl(P-P)]₃ complexes described in this study are effective catalyst precursors for the hydrogenation of various alkene, ketone, imine, and nitrile substrates under relatively mild conditions (30-100 °C, 1-12 atm of H₂). A detailed kinetic study on the hydrogenation of styrene catalysed by [RuCl(DPPB)(µ-Cl)]₂ shows a first-order dependence of the maximum rate on catalyst concentration, a first- to zero-order dependence on styrene concentration and a zero- to first-order dependence on the H₂ pressure. A mechanism involving formation of the molecular hydrogen (η²-H₂) complex (see above) followed by hydrogen transfer to the substrate is proposed to account for the observations, and the rate constants at 30 ºC for the various steps have been determined. Preliminary data on acetophenone and benzonitrile hydrogenation shows that the trinuclear hydride complexes are an order of magnitude more effective than the corresponding dimeric precursors. / Science, Faculty of / Chemistry, Department of / Graduate

M.Sc. (Chemistry) / Please refer to full text to view abstract

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

A new class of ruthenium-COD complexes containing carbon-bridged carboranyl-cyclopentadienyl (-indenyl or -fluorenyl) ligands was synthesized. These complexes showed a different reactivity in COD displacement reactions in comparison with the classical LRuCl(COD) (L = Cp, indenyl) complexes presumably due to the presence of sterically bulky and constrained organic-inorganic hybrid ligands. However, the COD ligands in these complexes can be replaced by bidentate tertiary phosphines, 2,2'-bipyridine, mono-phosphites with small cone angles, primary amines or N-heterocyclic carbene to give the corresponding COD displacement complexes. The ruthenium-amine complexes are much more labile than the ruthenium-COD ones. The amine ligands can be substituted by CH3CN to afford more active ruthenium-acetonitrile complex. / Reactions of dilithium salt of linked cyclopentadienyl-carboranyl ligands with 1 equiv of RuCl2(PPh3)3 in THF afforded the corresponding doubly-linked cyclopentadienyl-carboranyl ruthenium(II) hydride complexes. Such intramolecular coupling of a cyclopentadienyl with an o-carboranyl unit is driven by steric factors. Both carboranyl and phosphines with large cone angles are essential for such coupling reactions. The doubly-linked cyclopentadienyl-carboranyl compound was released from the corresponding ruthenium hydride complex by treatment with excess HBF 4&middot;OEt2, followed by hydrolysis. This ligand is not accessible by any other known methods. / Reactions of the ruthenium-acetonitrile complex with SiMe3 substituted alkynes afforded mononuclear bis(vinylidene)metal or vinylvinylidenemetal, respectively, indicating that sterically demanding ancillary ligand and bulky alkynes are both important components to stabilize the above complexes. Treatment of the ruthenium-acetonitrile complex with internal alkynes afforded eta 4-Ru cyclobutadiene or ruthenacyclopentatriene complexes, respectively. Interestingly, interaction of ruthenium-acetonitrile complex with terminal aromatic alkynes gave ruthenium tricyclic complexes involving coupling reactions between Cp and alkynes. The possible reaction mechanism was proposed with the help of the DFT calculations. / Reactions of the ruthenium-amine complex with alkynes gave ruthenium aminocarbene or enamine complexes depending on the electronic properties of alkynes. Electron-rich alkynes gave aminocarbene complexes, whereas electron-deficient alkynes afforded enamine ones. The [eta5:sigma-Me 2C(C5H4)(C2B10H10)]Ru fragment remained intact during the reactions, which may play a role in these controlled reactions. / Sun Yi. / "May 2006." / Adviser: Zuowei Xie. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6398. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 157-177). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.