Catalytic transformations based on bond activation reactions using cobalt and rhodium complexes

The transition-metal mediated activation and functionalization of carbon-hydrogen bonds offers great potential for novel routes to important intermediates, improving feedstock economics and product diversity. Issues like selectivity, atom economy and catalytic efficiency are important parameters for the use of a transition metal catalyst. The objective of this thesis was to develop catalytic processes which are based on selective and efficient C-H bond activation reactions in order to combine this reactivity with functionalization reactions resulting in catalytic turnover to generate new, useful products.; Chapter 1 describes the synthesis of [C5Me5CO(C 2H3SiMe3)2], 1, and the reactivity of this labile olefin complex in H/D exchange reactions with benzene-d6. Chapter 2 introduces the use of 1 as a catalyst for the intermolecular hydroacylation of vinylsilanes, using aromatic aldehydes, as substrates. Chapter 3 extends this reactivity to alkylaldehydes and details the mechanism of this transformation. Resting states and deactivation routes are identified. This analysis indicates that aldehyde activation, olefin insertion and CO insertion steps are all reversible while the reductive elimination of ketone product is the turnover limiting step. Chapter 4 investigates the unique coordination chemistry of phthalaldehyde bound to the [C5Me5CO] fragment. Chapter 5 details the reactivity of 1 and its bis-ethylene analog towards Ph2SiH2. The formation of a cobalt(V) bis-silyl bis-hydride species is observed. Chapter 6 describes the reactivity of 1 towards silanes and catalytic hydrosilation reactions of aromatic ketones. Also the reactivity of 1 with a variety of aromatic carbonyl substrates is investigated. Chapter 7 introduces the reaction chemistry of 1 with pyridine and bipyridine.; In part II of this work analogous rhodium complexes are used to effect catalytic reactions based on C-H bond activation chemistry. Chapter 1 introduces a series of rhodium olefin complexes and details their reactivity in catalytic intramolecular transfer hydrogenation reactions. Chapter 2 describes the use of [C5Me5Rh(C2H3SiMe3) 2] as a catalyst for the selective addition of olefins to aromatic ketones. Chapter 3 reports initial results for the use of rhodium olefin complexes as catalysts for the isomerization of aldehydes and the transfer formylation of aldehydes.