Activation of Dioxygen by Dimethylplatinum(II) Complexes

Abstract

The ligands RN(CH2-2-C5H4N)2 (L1, R = CH2CH2OH; L2, R = CH2CH2CH2OH; L3, R = 2-C6H4OH) have been designed to give dimethylplatinum(II) complexes that can activate dioxygen in the absence of a protic solvent. The ligands react with [Pt2Me4(SMe2)2] to give an equilibrium mixture, with the major constituent being [PtMe2(κ2-N,N′-L)] (1a, L = L1; 1b, L = L2; 1c, L = L3). In the absence of air, 1a reacts with solvent CH2Cl2 to give [PtMe2(CH2Cl)(κ3-N,N′,N″-L1]Cl, while 1c decomposes with loss of methane to give [PtMe(κ3-N,N′,N″-L3-H)] and then, by reaction with solvent, the binuclear complex [{PtMe(κ3-N,N′,N″-L3-H)}2(μ-H)]Cl. In the presence of oxygen the complexes 1 in CH2Cl2 solution react to give [Pt(OH)Me2(κ3-N,N′,N″-L)]Cl, when L = L1 or L2, or [Pt(OH)Me2(κ3-N,N′,O-L-H)], when L = L3. The complex [Pt(OH)Me2(κ3-N,N′,N″-L2)]Cl decomposed in the presence of air to give the binuclear complex [{PtMe2(2-C5H4NCO2)(μ-OH)}2]. The factors influencing reactivity and mechanism in these reactions are elucidated, and th...