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 Pt0 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 PtII 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.