A reaction of [2,6-(tBu2PO)2C6H3]NiSCH2Ph with BH3·THF: borane mediated C–S bond cleavage

Abstract

C–S bond activation of thiophenols and mercaptans is of great importance but has rarely been reported. In this paper we report the C–S bond cleavage of the thiolato ligand of [2,6-(^tBu₂PO)₂C₆H₃]NiSCH₂Ph (1) mediated by BH₃·THF. The treatment of 1 with an excess amount of BH₃·THF in THF at room temperature afforded the borohydride complex [2,6-(^tBu₂PO)₂C₆H₃]Ni(η²-BH₄) (2) as the only product. The reaction of 1 with 2 equiv. of BH₃·THF in THF at room temperature for 48 h produced the hydride complex [2,6-(^tBu₂PO)₂C₆H₃]NiH (3) and the mercapto complex [2,6-(^tBu₂PO)₂C₆H₃]NiSH (5). As a new complex, 5 was also independently synthesized by a salt metathesis reaction of the corresponding chloride complex with NaSH and fully characterized by multinuclear NMR, FTIR, HRMS, X-ray crystallography and elemental analysis. A possible mechanism for the formation of 5 was proposed. It was supposed that 5 formed through BH₃ mediated C–S bond cleavage of the thiolato ligand of 1. The result would initiate further studies on the transition metal catalyzed borane mediated C–S bond activation of mercaptans.