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-PiPr2-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, (PPSArP)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 1a,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.