Investigation of new coordination modes for coordinatively unsaturated (dithiolato)cobalt(III) complex [(η5-Cp)Co(l,2-S2C2B10H10-s,s′)]

Abstract

A mononuclear 16-electron Cp-cobalt(III)-dithiolate complex of the general formula [(η5-Cp)Co(CabS,S′)] (2) (CabS,S′ = l,2-S2C2B10H10-S,S′) has been prepared by treatment of CpCo(CO)I2 with the corresponding dilithium dithiolato ligand Li2CabS,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, [(η5-Cp)Co)2(CabS,S′)] (3). A second new bonding mode for 2 was generated by treatment of 2 with Lewis bases (L) to give [η5-Cp)Co(CabS,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 [(η5-Cp)Co(CabS,S′)(η1-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 [η5-Cp)Co(CabS,S′)(L)] [L = η5-CpCo-S,S′ (3), η1-R1C-CR2S (6: R1 = R2 = COOMe (6a); R1 = H R2 = Ph (6b); R1 = H R2 = SiMe3 (6c))] are reported. In addition, the solid-state structures of 3, 4b, 5, and 6a were characterized by single-crystal X-ray analyses.