Co activation by (diphosphane)platinum(0): Carbonate and acetone formation - Experimental and mechanistic study

The platinum(II) complex [(dcpp)Pt(C₇H₇)H] (1) [dcpp = 1,3-bis(dicyclohexylphosphanyl)propane] reacts under 1 atm of CO to form the bis(carbonyl) complex of Pt⁰, [(dcpp)Pt(CO)₂] (2). Complex 2 slowly crystallizes in toluene solution to form crystals of the Pt ⁰ dimer [(dcpp)(η¹-CO)Pt{μ-C(O)}Pt(dcpp)] (3) in which one Pt atom is only three-coordinated with the diphosphane dcpp and one μ-C(O), while the other is coordinated in a tetrahedral arrangement with one μ-C(O) and one η¹-CO. Complexes 2 and 3 were characterized in solution by ³¹P NMR spectroscopy, and complex 3 readily reacts with O₂ to form the carbonate complex, [(dcpp)Pt(CO₃)] (4). The reaction of the dimeric complex 3 with MeI allows the insertion of a methyl group into the carbonyl group to form the Pt^II complex [(dcpp)Pt(C(O)Me)I] (5). Reaction of another equivalent of MeI with complex 5 leads to the formation and elimination of acetone and the bis(iodide) complex [(dcpp)PtI₂] (6). X-ray crystal structures of complexes 3 and 4 are reported along with DFT calculations and mechanistic studies of the formation of 3, 4, 5, and 6.