Synthesis, crystal structure, and stereochemical characterization of [Co4(η5-C5Me5)2(CO)4(µ2-CO)(µ3-CO)2]: a completely bonding tetrahedral cobalt cluster formed from a cobalt–cobalt multiple-bonded dimer

Abstract

A new type of tetrahedral metal cluster, [Co₄(η⁵-C₅Me₅)₂(CO)₄(µ₂-CO)(µ₃-CO)₂](1), has been prepared by the reaction of neutral [Co₂(η⁵-C₅Me₅)₂(µ₂-CO)₂](2) with dicobalt octacarbonyl as well as by the oxidation of the monoanion of (2) with toluene-p-sulphonic acid in the presence of NaCo(CO)₄; a structural analysis by X-ray diffraction revealed that (1) may be viewed, at least conceptually, as an adduct formed by the net insertion of a Co₂(CO)₄(µ₂-CO) fragment across the Co–Co double bond of (2).