Oxidation of dimethyldi(2-pyridyl)borato PtIIMen complexes, n = 1, 0, with H2O2: tandem B-to-Pt methyl group migration and formation of C–O bond

Abstract

New dimethyldi(2-pyridyl)borato (dmdpb) platinum(II) complexes, (dmdpb)Pt^IIMe(SMe₂) (1), (dmdpb)Pt^II(L)(SMe₂)⁺, L = MeOH (2), MeCN (3), supported by dimethylsulfide ligand and featuring one (1) or no hydrocarbyls at the metal (2, 3) were prepared and their oxidation with hydrogen peroxide was studied. Both complex 1 bearing the formal charge of +1 on the metal and the methanol complex 2 capable of losing the proton of the methanol ligand to form the methoxide derivative 4 charged similarly to 1, are reactive towards H₂O₂. However, the cationic complex 3 with a formal charge of +2 on the metal does not react with H₂O₂. The oxidation of the monomethyl platinum(II) complex 1 leads to the B-to-Pt methyl transfer and formation of a robust dimethyl Pt^IV species 5 which does not undergo C–O reductive elimination up to 100 °C. By contrast, oxidation of 2 in methanol-d₄ leads to quantitative formation of dimethyl ether-d₃, CD₃OCH₃. It was presumed that the latter reaction involves the B-to-Pt methyl transfer and formation of a highly reactive cationic monomethyl Pt^IV species whose methyl group carbon atom can accept nucleophilic attack by the methanol-d₄ solvent to form dimethyl ether-d₃.