Electrochemical behavior of the Cp*(dithiolato)Co(III) complex [(η5-Cp*)Co(1,2-S2C2B10H10-S,S′)] and its derivatives: the effect of the ligand on half-sandwich cobalt(III) complexes

Reaction of the 16-electron dithiolatocobalt, [(η5-Cp*)Co(CabS,S′)] (1) (CabS,S′=1,2-S2C2B10H10-S,S′), with a ligand L (L=CNtBu, PMe3, PEt3, PHPh2) affords the 18-electron complexes [(η5-Cp*)Co(CabS,S′)(L)] (2) in high yield. The structures of 2 in solution were probed by NMR spectroscopy, and the solid-state structure of the diphenylphosphine derivative was established by single-crystal X-ray diffraction. Cyclic voltammetry of 1 shows that the complex undergoes a quasi-reversible one-electron oxidation and reversible reduction. The voltammetry of the corresponding 18-electron complex 2 was investigated rather extensively in terms of coordination and redox chemistry, in which the influence of the enhanced steric interaction between the bulky Cp* and incoming ligand could be observed. Cyclic voltammograms of alkylidiene or acetylene adducts of dithiolatocobalt complex 1, [(η5-Cp*)Co{η3-(S,S′,C′)-SC2B10H10S(C′R2)}] [C′R2=CHSiMe3 (3a), HCCPh (3b), (COOMe)CC(COOMe) (3c)], are also included.