Synthesis and Reactivity of Transition Metal Methylidene Complexes

Citation

Finch, William C. (1986) Synthesis and Reactivity of Transition Metal Methylidene Complexes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/t0fa-0414. https://resolver.caltech.edu/CaltechTHESIS:10062009-112330268

Abstract

The reaction of metal oxo complexes with methylenation agents, "Cp₂TiCH₂" and CH₂PPh₃, was investigated as a means to generate new transition metal methylidene complexes. With "Cp₂TiCH₂", only when the oxo complex has ancillary ligands of the proper electronic and steric characteristics, as in WO(CH₂XMe₃)₄(X = C, Si), is clean reaction observed producing µ-O-µ-CH₂ complexes. Otherwise the many reaction pathways available to the Cp₂TiCH₂ fragment lead to complex reaction mixtures. The oxo ligand is inert to attack by CH₂PPh₃ which instead acts as a powerful alkylating agent in the transition metal systems investigated.

The effect of cyclopentadienyl ring substitution on the reactivity of titanocene metallacyclobutanes was also investigated. The observed decrease in reactivity of these compounds with increasing methyl substitution of their cyclopentadienyl rings is related to the increasing destabilization of the transition state between metallacycle and methylidene-olefin complex upon substitution. This destabilization arises from the "reductive" nature of the formation of methylidene-olefin complex from metallacycle.

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