Reactions of co-ordinated ligands. Part 46. Formation of [Os3(µ-H)(µ-CCH2CHMe2)(CO)10] and [Os3(µ-H)(µ-CCHCMe2)(CO)10] by carbon–carbon σ-bond and carbon–hydrogen activation of 3,3-dimethylcyclopropene; crystal and molecular structure of [Os3(µ-H)(µ-CCH2CHMe2)(CO)10] and evidence for its facile rearrangement to [Os3(µ-H)(µ-CHCHCHMe2)(CO)10]

Abstract

Reaction of [OS₃(µ-H)2(CO)₁₀] with 3,3-dimethylcyclopropene leads to both carbon–carbon σ-bond and carbon–hydrogen activation and formation of [OS₃(µ-H)(µ-CCH₂CHMe₂)(CO)₁₀](1) and [OS₃(µ-H)(µ-CCHCMe₂)(CO)₁₀](2). The former was characterised in solution by ¹H and ¹³C-(¹H) n.m.r. spectroscopy and in the solid state by single-crystal X-ray crystallography. The µ-CCH₂CHMe₂ and µ-H groups bridge the Os(1)–Os(2) bond almost symmetrically. Significantly, the alkylidyne carbon also interacts with the Os(CO)₄ unit. Reaction of [Os₃(µ-D)₂(CO)₁₀] with 3,3-dimethylcyclopropene leads to deuterium incorporation only into the Os(µ-D)Os and Os(µ-CCHDCHMe₂)Os sites, there being no deuterium incorporation into the vinyl-substituted µ-carbyne complex; mechanisms are discussed. Thermolysis of complex (1) leads to the sequential formation of [Os₃(µ-H)(µ-CHCHCHMe₂)(CO)₁₀] and [Os₃(µ-H)₂(µ-CCHCHMe₂)(CO)₉]. Photolysis of (1) directly affords the latter. The mechanism of the thermal reaction is discussed in terms of a 1,2-hydrogen shift process, which does not involve the metal centres.