Reversible Intramolecular P-S Bond Formation Coupled with a Ni(0)/Ni(II) Redox Process

Abstract

P-S bond formation/cleavage mediated by a nickel ion supported by a PPP ligand (PPP = P[2-(PPr2)-Pr-i-C6H4](2)(-)) has been investigated herein. To gain an entry into this chemistry, a mononuclear thiolato nickel complex, (PPP)Ni(SAr) (1a,b) was prepared by treating the chloride starting material with NaSPh. Upon carbonylation, this complex produces a nickel(0) monocarbonyl species, ((PPP)-P-SAr)Ni(CO) (2a,b), in which the thiolate migrates onto the central P of the ligand to give a P-S bond and two electron reduction of a nickel(II) center. The reaction undergoes via a pseudo-first-order decay with respect to consumption of a nickel(II) thiolato species, suggesting an intramolecular reaction under the excess CO(g) conditions. The reverse reaction involving P-S bond cleavage with concomitant decarbonylation occurs to regenerate 1 a,b in benzene. Reaction of 2a with trityl chloride results in Ph3CSPh formation, whereas the reaction with MeI gives methylation at a phosphide moiety or a thiolate group.