A cooperative pathway for water activation using a bimetallic Pt0–CuI system

Abstract

A mixture of the platinum(0) complex [Pt(P^tBu₃)₂] and tetrakis(acetonitrile)copper(I) hexafluorophosphate in acetone activated a water molecule and gave the hydride platinum(II) complex [PtH(CH₃CN)(P^tBu₃)₂]PF₆, 1, and the hydroxide Cu(I) species. The crystal structure of complex 1 was determined by X-ray crystallography, indicating a distorted square planar geometry around the platinum center. Although three possible mechanisms are proposed for this transformation, monitoring of the reaction using NMR spectroscopy at low temperature reveals that a cooperative pathway involving formation of a Pt⁰–Cu^I dative bond complex is the most probable pathway. The hydride platinum complex 1 is stable in acidic and neutral conditions but undergoes intramolecular C–H activation in the presence of pyridine. Monitoring of the reaction using ¹H and ³¹P NMR spectroscopy shows that a cyclometalation reaction of one of the phosphine ligands is followed by displacement of a second phosphine ligand by pyridine to give the cyclometalated platinum(II) complex, [Pt(κ²_PC-P^tBu₂CMe₂CH₂)(py)₂], 4. The structure of 4 in solution and solid state phases was determined using NMR spectroscopy and X-ray crystallography, respectively.