HRu3(CO)10(COCH3). A cluster with an oxygen-containing μ2-carbyne ligand; preparation,structure and fluxionality

The cluster HRu₃(CO)₁₀(COCH₃) has been prepared from NaHRu₃(CO)₁₁] and (CH₃)₃O]BF₄ in acetonitrile. The complex crystallises in the monoclinic space group P2₁/c, with cell dimensions a 7.937(2), b 16.880(9), c 14.074(3) Å, β 104.16(3)° and Z 4. The structure was solved by a combination of Patterson and Fourier techniques and refined by full-matrix least-squares to final residues of R = 0.031 and R_w = 0.035 for the 2529 unique intensities. The three ruthenium atoms define an approximately equilateral triangle with one edge bridged by both a μ₂-H and a μ₂-COCH₃ ligand. The fluxional behaviour of HRu₃(CO)₁₀-(COCH₃) has been studied by variable temperature ¹³C NMR spectroscopy. The spectra are indicative of several dynamic processes occurring in solution over the range ?100 to +90°C. The μ₂-COCH₃ species can be considered as a bridging three-electron donor and thus represents a μ₂-carbyne ligand.