Scott, Susannah L.,Rice, Gordon L.2009-03-232009-03-2319991999Source: Dissertation Abstracts International, Volume: 61-02, Section: B, page: 0851.9780612465404http://hdl.handle.net/10393/8680http://dx.doi.org/10.20381/ruor-15939This thesis has been divided into three major sections. The first section deals with the preparation and characterization of silica-supported vanadium(V) complexes. The reactions of O=VX3, X = Cl or OiPr, with the surface of partially dehydroxylated silica gives a single well-defined surface complex, ≡SiOVOX2. These complexes have been characterized by 51V magic angle spinning and 13C cross-polarization magic angle spinning NMR spectroscopy and infrared spectroscopy. The incorporation of 18O labels into specific positions of the silica-supported vanadium complexes has been achieved. When the hydroxyl groups are first exchanged with H218O, the subsequent reaction with O=VX 3 gives exclusively ≡SI18OV16OX 2. Reaction of 18O=VCl3 with unlabelled silica gives only ≡Si16OV18OCl2. The surface complexes undergo clean ligand replacement without displacing or diluting the isotope labels. Other reactions are investigated which are analogous to molecular vanadium reactions and relevant to the understanding of mechanisms in heterogeneous catalysis. The second section deals with a special type of reactivity of silica-supported vanadium(V) complexes. A nonhydrolytic low-temperature route to ternary V-Ti-Si catalysts has been developed. Ti(OiPr)4 migrates underneath the silica-supported vanadium overlayer to give a heterobinuclear complex containing one Ti per V, bound to the silica surface via Si-O-Ti linkages. When Ti(OiPr)4 reacts with the surface of partially dehydroxylated silica, a dinuclear species is formed. Because of this reaction it was not possible to form the mixed Ti-V species by depositing the Ti first. However once a method was developed for the formation of mononuclear silica-supported titanium complexes, we demonstrate that indeed the heterobinuclear species can also be formed by the reaction of O=V(OiPr)3 with ≡SiOTi(OiPr)3. Although there is precedence in the literature for nonhydrolytic condensation of metal chloride alkoxides, this is the first example of such a stoichiometric reaction on a surface. The last part of this thesis deals with the study of silica-supported organovanadium species. The reaction of V(CH2SiMe3) 4 with the surface of partially dehydroxylated silica gives exclusively (≡SiO)2V(CH2SiMe3)2. This surface complex undergoes a surprisingly clean thermal transformation to generate a supported alkylidene complex, (≡SiO)2V=CHSiMe3, with concurrent liberation of SiMe4. The reaction is quantitative and kinetically first order. The mechanism is believed to be a surface assisted alpha-H elimination. The unusual supported vanadium alkylidene reacts with olefins in the absence of alkylaluminum cocatalysts.177 p.Chemistry, Inorganic.Thesis