Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 127-134.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006. / Prof. Will Rees, Committee Member ; Prof. Charles Liotta, Committee Member ; Prof. David Collard, Committee Member ; Prof. Marcus Weck, Committee Chair ; Prof. Kent Barefield, Committee Member.

Thesis (PhD)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: Christoph G. Rose-Petruck. Includes bibliographical references (leaves 95-107). Also available online.

The synthesis, reactivity, and spectroscopic properties of a series of triangular phosphido-bridged rhodium, iridium, palladium and platinum clusters are described. Throughout the project, X-ray diffraction and 31P{1H} NMR spectroscopy are the main techniques for characterizing compounds. In the first part of this report, the lability of μ-X and terminal phosphines in [M3(μ-X)(μ-PPh2)2(PPh3)3)[BF4](M= Pd, X= Cl; M=Pt, X= H) is utilized to prepare a number of compounds where the integrity of the triangular framework is maintained. The molecular structures of three representative examples: [Pd3(μ-SCH2Ph)(μ-PPh2)2(PEt3)3][BF4] [Pt3(μ-Cl)(μ-PPh2)2(PR3)3][BF4) (R= Ph, Et) were determined and are described. Reaction of these palladium and platinum trinuclear clusters with chelating ligands, R’2PYPR”2 (Y= O, CH2), results in unusual cluster fragmentation to give novel dinuclear monocations, [M2(μ-PP2)(μ-R’2PYPR”2) (PR3)2)+ (M= Pd, Pt) in which a metal-metal bond is supported by both dppm and phosphido bridges. These dimers are very inert failing to react with a number of reagents including C4H6, HCCCO2Me, CH2N2, CO, CH3I (when M= Pd), H2, HBF4 and CH2I2. The cluster, [Pt3(μ-H)(μ-PPh2)2(PPh3)3] [BF4], also reacts with ButNC to afford the dinuclear species (Pt2(μ-PPh2)2(ButNC)(PPh3)3]+. The crystal structures of fragmentation products [Pd2(μ-PPh2)( μ-Pri2PCH2PPh2)(PPh3)2] [BF4], (Pt2(μ-PPh2)( μ-Me2PCH2PMe2)(PPh3)2]2 [C2O4] and (Pt2(μ-PPh2)(ButNC)(PPh3)3]2(C2O4) are reported and discussed. In the last part, the synthesis of a novel trinuclear iridium cluster, [Ir3(μ-PPh2)3(CO)5], is described, and the reactions of this cluster and its previously reported rhodium analogue, [Rh3(μ-PPh2)3(PPh3)2(CO)3], with dppm afford not fragmentation, but substitution products. The complex (Ir3(μ-PPh2)3(CO)5] also reacts with ButNC to yield [Ir3(μ-PPh2)3(CO)5(ButNC)2]. The crystal structures of the compounds, [M3(μ-PPh2)3(μ-dppm)(CO)3] (M= Rh, Ir) and (Ir3(μ-PPh2)3(CO)5(ButNC)2], are also reported. / Graduate

No description available.

The scope of the palladium catalysed allylic substitution reaction is reviewed with particular reference to stereocontrol. The use of enantiopure oxazolines and acetals in asymmetric synthesis is briefly outlined. The work presented is concerned with the design and construction of enantiopure ligands which are able to impart very high levels of enantioselectivity in the aforementioned palladium-catalysed allylic substitution reaction. The ligands exploit the stereochemistry-controlling properties of the oxazoline moiety, whilst incorporating a secondary donor atom. The ligands rely upon an electronic disparity between these two atoms to direct nucleophilic addition.

The preparation of the modified silane [special characters omitted]; a phosphinoalkylsilane or PSi) via an alkylzirconium intermediate is reported. The synthesis of [special characters omitted] was carried out by the reaction of organolithium reagents with chloro-silanes at low temperature. The PSi compounds are isolated as air-sensitive, thermally stable and very viscous liquids. The reactivity of two of the silanes was investigated with the platinum group metal complex [special characters omitted] (cod = cycloocta-1,5-diene). In both cases, square planar platinum (II) complexes were isolated. The reactivity of [special characters omitted] produces five coordinate M (III) complexes which undergo stereomutation. The isomerisation of the syn to anti forms of [special characters omitted] has been examined at several temperatures via NMR spectroscopy and the activation parameters determined for the conversion of the syn to the intermediate isomer form [special characters omitted]. The implications of the stereomutation phenomona are discussed in relation to catalysis. None of the isomers of this complex forms a stable six coordinate adduct when reacted with a number of common nucleophiles. The analogous compound where M = Ir and related complexes of the formula [special characters omitted] are reactive towards CO to form stable six coordinate adducts containing two M-P and one M-Si, M-H, M-CO and a M-Cl bond. Some of these adducts can be made directly by the reaction of the PSi ligand precursor with [special characters omitted] (M = Rh, Ir) at room temperature. The reaction of the silane [special characters omitted] produces six coordinate complexes directly. For M = Ir, the compound reacts with CO to produce a six coordinate cation by displacement of a chloride ligand, the latter of which then acts as a non-coordinating counterion. A series of organosilicon dendrimers of the type : [special characters omitted] ([G-1] : x = 3, y = 2 = q = 0; [6-2] : y = 3, x = 9 , z = q = 0; [G-3] : z = 3, y = 9, X = 27, q = 0; [G-4] : q = 3, z = 9, y = 27, x = 81) are sythesised and examined spectroscopically. All of the dendrimers are air stable liquids. Species G3 has a marked tendency to undergo what appears to be self-condensation polymerisation. End and core group substitution is presented for a carbosilane dendrimer containing one shell of identical exterior Si atoms. The dendrimeric end groups can be modified by the replacement of a terminal chloride by fluoride, hydrogen, alkyl groups or metal complexes. The selective removal of a core phenyl group can be accomplished with the strong acid [special characters omitted]. The resulting silyl triflate can in turn be used as a precusor to a silyl ether, hence facilitating selective core group modification. / Graduate

A series of mononuclear complexes of general formula [M(η5-C5Me5)Cl3-n(pzH)n](n-1)+ (n = 1,2) has been prepared as a result of an investigation of the reactivity of pyrazole with rhodium and iridium cyclopentadienyl and pentamethyl-cyclopentadienyl precursors. These complexes are discussed in terms of the dynamic processes that are exhibited in the 1H NMR experiment and in terms of their use as precursors to dimeric species. Dinuclear complexes of formula [M(η5-C5R5)Cl(μ-pz)]2 containing pyrazolyl bridges have been prepared from the mononuclear compounds and from the chloro-bridged dimers of formula [M(η5-C5R5)Cl2]2 by treatment with triethylamine, but not from the dipyrazole iridium cation [Ir(η5-C5Me5)Cl(pzH)2]+ 26 which has been found to be unreactive to this type of symmetrical dimer formation: the low reactivity is attributed to a relative non-lability of the pyrazole groups. The dimeric complexes have been shown to undergo a core conformational change upon chemical reduction or halide abstraction. The chair conformation of the pyrazolyl bridged complex [Rh(η5-C5ME5)Cl(μ-pz)]2 38 has been proven crystallographically. Chloride abstraction from 38 yields the binuclear product [(Rh(η5-C5ME5)(μ-pz))2(μ-Cl)]BF4 46 which is bridged by two pyrazolyl and one chloride ligand and has been structurally characterized by X-ray diffraction to contain a boat conformation for the pyrazolyl framework. Reduction of either 38 or the C5H5 analogue 40 results in the metal-metal bonded dinuclear complexes [Rh(η5-C5ME5)(μ-pz)]2 48 and 49. The C5H5 complex 49 has been crystallographically determined to possess the boat conformation. The reactivity of the metal-metal bonded products has been investigated: one and two fragment addition is discussed and a number of oxidative addition products have been structurally characterized. The mononuclear dipyrazole iridium cation 26 which contains non-labile pyrazole groups is utilized to prepare mixed-metal and mixed-oxidation state dimers with the formula [Ir(η5-C5Me5)Cl(μ-pz)MLn]. The synthesis and potential for further investigation of these complexes is discussed. / Graduate

No description available.