No description available.

The synthesis of a variety of new lanthanoid phosphine complexes has been achieved by complexing either one or two amido-diphosphine ligands to yttrium, lutetium or lanthanum. At room temperature, the seven-coordinate bis(amido- diphosphine) complexes, MCl[N(SiMe₂CH₂PR₂)₂]₂- are fluxional and display NMR spectra indicative of complexes where the phosphorus donors are rapidly exchanging, probably via a dissociation-reassociation pathway. It is possible to generate thermally unstable hydrocarbyl complexes of the type, M(R)[N(SiMe₂CH₂PMe₂)₂]₂, which undergo a clean first order elimination of R-H to generate cyclometallated complexes of the type, M[N(SiMe₂CHPMe₂)(SiMe₂CH₂PMe₂)][N(SiMe₂CH₂PMe₂)₂]; the yttrium derivative was crystallographically characterized. These thermally robust compounds will undergo a-bond metathesis with H₂ and D₂ at high temperature, but appear to be too sterically congested to react with larger molecules. The synthesis of a series of mono(amido-diphosphine) lanthanoid complexes, MCl₂ [N(SiMe₂CH₂PR₂)₂], (R = Me, Ph, Pr', Bu[symbol omitted]) has also been achieved. Complexes of the type, MCl₂[N(SiMe₂CH₂PMe₂)₂], are insoluble in hydrocarbon solvents, presumably because they are oligomeric in nature. They will however, dissolve in THF probably forming seven-coordinate bis(THF) monomers. Attempts to alkylate these compounds generally led to decomposition; the cyclometallated bis(ligand) complex, M[N(SiMe₂CHPMe₂)(SiMe₂CH₂PMe₂)] [N(SiMe2CH2PMe2)2], was identified as the major product. A route to a dimeric mono(amido-diphosphine) allyl complex, {YCl(allyl)[N(SiMe₂CH₂PMe₂)₂]}₂ (characterized by crystallography) was found via the reaction of allyl-MgCl or Mg(allyl)₂(dioxane) with YCl[N(SiMe₂CH₂PMe₂)₂]₂. The mono(ligand) complexes containing bulky phosphine donors (R = Ph, Bu[symbol omitted], Pr[symbol omitted]) are soluble in hydrocarbon solvents; YCl₂[N(SiMe₂CH₂PPr[symbol omitted]₂)₂] can be isolated as either a THF adduct or as the base-free dimer. A new reaction, mediated by a zirconium or hafnium amido-diphosphine complex, where allyl and butadiene moieties are coupled together to generate a coordinated [ɳ⁴:ɳ¹-CH₂=CHCH=CHCH₂CH₂CH₂]¹- fragment has been investigated. The process is very sensitive to the nature of the ancillary ligands at the metal. For MCl(ɳ⁴-C₄H₆)[N(SiMe₂CH₂PR₂)₂] complexes, after the addition of allylMgCl, the transformation takes about one hour when M = Hf & R = Pr[symbol omitted], two hours when M = Zr & R = Pr[symbol omitted], a week when M = Hf & R = Me, and results only in decomposition when M = Zr & R = Me. Similarly, for the zirconium mediated coupling of 1-methylallyl with butadiene, when R = Me, decomposition occurs and when R = Pr[symbol omitted], after two hours the coupling is complete. Two of the four possible coupled products are formed in unequal amounts, and the coupling occurs exclusively at the substituted end of the 1-methylallyl unit as determined by X-ray crystallography. Which diastereomer is formed in excess was not determined. The reduction of ZrCl₃[N(SiMe₂CH₂PR₂)₂] (R = Pr[symbol omitted] or Bu[symbol omitted]) with Na/Hg amalgam under nitrogen results in the formation of a binuclear zirconium dinitrogen complex, {ZrCl[N(SiMe₂CH₂PR₂)₂]}₂ (μ-ɳ²:ɳ²-N₂). X-ray crystallography (for R = Pr[symbol omitted]) reveals that the N₂ ligand is symmetrically bound in a side-on fashion to both metals. In addition, the N—N bond length of 1.548 (7) Å, the longest bond length ever reported for a dinitrogen complex, indicates that the dinitrogen has been reduced to a N₂⁴⁻ hydrazido ligand. Protonation of the complex with HCl results in a quantitative formation of hydrazine. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Lo, Kwok Cheung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 114-118). / Abstracts in English and Chinese. / Thesis / Assessment Committee --- p.ii / ABSTRACT --- p.iii / ACKNOWLEDGEMENTS --- p.v / TABLE OF CONTENT --- p.vi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Theoretical Background --- p.5 / Chapter Chapter 3 --- Results --- p.38 / Chapter Chapter 4 --- Discussion and Concluding Remarks --- p.85 / LIST OF TABLES / Table / Table la Electronic energies and geometrical parameters of scandium dicarbide by B3LYP/LANL2DZ and B3LYP/LANL2DZ-d --- p.41 / Table lb Comparison of literature results with current computational results of cyclic scandium dicarbide at equilibrium state by B3LYP/LANL2DZ and B3LYP/LANL2DZ-d --- p.42 / Table lc Comparison of literature results with current computational results of linear scandium dicarbide at equilibrium state by B3LYP/LANL2DZ and B3LYP/LANL2DZ-d --- p.43 / Table 2a Electronic energies and geometrical parameters of titanium --- p.46

Graduation date: 1993

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 137-147).