Investigation of new coordination modes for coordinatively unsaturated (dithiolato)cobalt(III) complex [(η5-Cp)CO(1,2-S2C2B10H10-S,S′)]

A mononuclear 16-electron Cp-cobalt(III)-dithiolate complex of the general formula [(eta(5)Cp)Co(Cab(S,S'))] (2) (Cab(S,S') = 1,2-S2C2B10H10-S,S') has been prepared by treatment of CpCo(CO)I-2 with the corresponding dilithium dithiolato ligand Li(2)Cab(S,S') (1). Experiments aimed at the characterization of new coordination modes for 2 are described. The reaction of 2 with BH3.THF produces an unexpected bimetallic cobalt dithiolate complex, [((eta(5)-CP)CO)(2)(Cab(S,S'))] (3). A second new bonding mode for 2 was generated by treatment of 2 with Lewis bases (L) to give [(eta(5)-Cp)Co(Cab(S,S'))(L)] (L = CNBut (4a), PEt3 (4b)), the 18-electron species of which consists of a mononuclear 2 coordinated through a dative Co-L bond. A third new bonding mode for 2 is illustrated by [(eta(5)-Cp)Co(Cab(S,S'))(eta(1)-CH2SiMe3-S)] (5). Reaction of 2 with (trimethylsilyl)diazomethane resulted in the formation of the alkylidene-bridged complex 5, containing a Co-C-S three-membered ring. The formation of 4 and 5 has also been investigated electrochemically. Consequently, the addition of organic and organometallic compounds into the Co-S bond of 2 has been investigated. Thus, the syntheses of half-sandwich cobalt(III) complexes [(eta(5)-Cp)Co(Cab(S,S'))(L)] [L = eta(5)-CpCo-S,S' (3), eta(1)-R-1,C=CR2-S (6: R-1 = R-2 = COOMe (6a); R-1 = H R-2 = Ph (6b); R-1 = H R-2 = SiMe3 (6c))] are reported. In addition, the solid-state structures of 3, 4b, 5, and 6a were characterized by single-crystal X-ray analyses.