No description available.

No description available.

No description available.

No description available.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 45-49. / by Mark Joseph Lupo. / M.S.

The compound Ru⁺²(CO)₃Cl₂(THF) spontaneously adsorbs onto MgO, Al₂O₃, SiO₂, and NaY zeolite from THF solution evolving less than 0.1 equivalent of CO to yield a light yellow supported complex. Based on reaction stoichiometry, CO evolution and in situ infrared spectroscopy, the adsorption was found to produce two different surface-bound species depending on the support used. On SiO₂ and NaY zeolite, the surface species Ru⁺²(CO)₃Cl₂(SURFACE) is formed by a ligand substitution of THF for a surface hydroxyl group. When the adsorption is performed on MgO or AI₂O₃, the inorganic oxide acts as a chloride acceptor to form the surface species Ru⁺²(CO)₃(SURFACE)₃. A molecular analog of the adsorbed species Ru(CO)₃Cl₂(SURFACE) was synthesized and characterized by infrared spectroscopy, ¹H NMR, and an X-ray crystal structure. The infrared spectra of the adsorbed species, Ru(CO)₃Cl₂(SURFACE), and the model compound were in close agreement. Model compounds of Ru(CO)₃(SURFACE)₃ were also synthesized: however, these could not be structurally characterized. The reactivity of the adsorbed species, Ru(CO)₃Cl₂(SURFACE) and Ru(CO)₃(SURFACE)₃, towards the formation of supported bimetallics, polynuclear ruthenium carbonyl clusters, and ruthenium bipyridine coordination compounds was investigated. On SiO₂ and NaY zeolite, the chemistry of Ru(CO)₃Cl₂(SURFACE) paralleled that of Ru(CO)₃Cl₂(THF) in solution. On Al₂O₃ and MgO, the chemistry of Ru(CO)₃(SURFACE), was indicative of an adsorbed ruthenium carbonyl-containing no chloride ligands. The bimetallic cluster RuCo₃(CO)₁₂⁻ was synthesized on hydroxylated Al₂O₃ by the disproportionation of RuCo₂(CO)₁₁. The trimeric cluster RuCo₂(CO)₁₁ is spontaneously adsorbed onto AI₂O₃ from a pentane solution yielding the adsorbed species "RuCo₂(CO)₁₀", this was then transformed to the tetrameric cluster RuCo₃(CO)₁₂⁻ by the addition of THF. The adsorbed cluster anion RuCo₃(CO)₁₂⁻ could also be synthesized on AI₂O₃ by the deprotonation of the hydridic cluster HRuCo₃(CO)₁₂. Depending on the route, infrared evidence suggests formation of a solvated or unsolvated anion on the surface. / Ph. D.

Transition metal compounds such as Co₂(CO)₈ have often been used to catalyze various organic reactions. Severe difficulties may be encountered when attempts are made to recover and separate the soluble catalysts. A heterogeneous system consisting of Co₂(CO)₈ impregnated on zeolites with faujasitic structure has been designed and investigated using a variety of techniques. In situ FTIR spectroscopy and carbon monoxide evolution were used to identify the major products generated, namely Co₄(CO)₁₂ and Co(CO)_4^-. Disproportionation may be induced thus forming Co(CO)_4^- and an associated cation from the supported subcarbonyls by addition of various ligands such as methanol. The location of the supported cobalt carbonyls is determined by their reactivity toward various phosphines with various kinetic diameters. The materials prepared in this manner were found to be active in catalyzing the methanol carbonylation reaction and following thermolysis were also found to be active Fischer-Tropsch catalysts. Major products observed in the carbonylation of methanol were methyl acetate and an acetaldehyde dimethyl acetal. The supported cobalt catalyst displays greater activity than Co₂(CO)₈ in solution for the carbonylation reaction when conducted under similar conditions. In the Fischer-Tropsch process, selectivity is seen for the production of linear, short-chain hydrocarbons. / Ph. D.

This student is interested in reinvestigating the kinetics and mechanism of the bridged compound in l,2-dichloroethane with triisopropyl phosphite and in finding the reasons why the values of competition ratio k₋₂ /k₃ in this reaction are so large.

The synthetic studies include the synthesis of the cyclic siloxydiyne, 3,3,5,5,8,8,10,10-octamethyl-4,9-dioxa-3,5,8,10-tetrasilacyclodeca-1,6- diyne [VI] and its novel iron carbonyl complex. In the preparation of [VI] by HBr promoted condensation of bis (methoxydimethylsilyl) acetylene, a minor product, a cyclic trimer was always formed along with the major product [VI]. No evidence of an equilibrium between the trimerization product and the dimerization product was found. Compound [VI] can react with iron carbonyl reagents to produce a novel binuclear iron complex of trimethylenemethane [VII] in very low yield either in a thermal or photo-reaction. The key step proposed by us in the formation of [VII] is a I,2-silyl shift in a complexed bis (silyl) acetylene to form a vinylidene intermediate. Experiments aimed at isolating this intermediate were not successful.

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Please see fulltext for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming