Transition metal-siloxide complexes; synthesis, structure and application to catalysis

Synthesis and structural characterization of molecular transition-metal (TM )-siloxide (TM-O-Si) complexes by X-ray spectroscopic and other physico-che mical methods reported since 1982 are reviewed. TM siloxides include termin al and/or bridging siloxy ancillary ligands. Stereoselective properties of the two forms of siloxide ligand have been employed as advanced models (e.g . incompletely condensed silsesquioxanes) of catalytically active centers o f early-TM complexes (mainly terminal structures) in such reactions as poly merization and metathesis of olefins and/or as precursors for catalysis by low-coordinate and low-oxidation state late-TM-complex catalysts (in the fo rm of bridging structures). (C) 2001 Elsevier Science B.V. All rights reser ved.