Synthesis, properties and characterization of the trinuclear clusters [Co-3(mu-SR)(6)(PEt(3))(3)]X (R=Me or Et, X=BPh(4)(-) or PF6-)

The reactions of methane- and ethane-thiol with cobalt(II) acetate in the presence of an excess of PEt(3) afforded the new clusters [Co-3(mu-SR)(6)(PEt(3))(3)]X (R = Me or Et, X = BPh(4)(-) or PF6-). A complete X-ray analysis of [Co-3(mu-SEt)(6)(PEt(3))(3)]BPh(4) revealed that in the cluster cation the three cobalt atoms are at the vertices of a regular triangle, with six equivalent symmetrically bridging thiolate ligands. A multinuclear magnetic resonance study showed that the singly charged duster molecules in solution maintain essentially the same conformation as in the solid state, the thiolate groups being involved in a rapid dynamic process. Electrochemical measurements showed that these cluster monocations undergo both a one-electron oxidation and a one-electron reduction. The latter is complicated by degradation of the corresponding neutral congeners. The electrogenerated paramagnetic compounds were studied by EPR analysis and the resulting features correlated with the results of an extended-Huckel molecular orbital study.