Organometallic compounds

Pt−Me bond cleavage in the reactions of dimethylplatinum(II) complexes containing chelating phosphine ligands with organotin(IV) chlorides

Selective Pt−Me bond activation of dimethylplatinum(II) complexes [PtMe2(PP)] (PP = dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane)) was achieved by SnMe2Cl2 to yield the corresponding platinum(II) complexes [PtMeCl(PP)] (PP = dppm, dppe, dppp) and cis-[PtCl2(PP)] (PP = dppm, dppp). On the other hand, the reactions of complexes [PtMe2(PP)] (PP = dppm, dppe, dppp) with SnPh3Cl resulted in the selective cleavage of the Pt−Me bond to afford the methylplatinum(II) complexes [PtMeCl(PP)]. Notably, the reaction of [PtMe2(dppm)] with SnMe2Cl2 and SnPh3Cl also gave the ionic A-frame complex [Pt2Me2(μ-Cl)(μ-dppm)2]Cl. The variable-temperature 1H and 31P NMR spectroscopy shows that the cleavage of the Pt−Me bond occurs very rapidly and the short-lived platinum(IV) intermediate is difficult to detect during the reaction. An explanation is presented on the basis of the nature of the strong π-acceptance of the phosphine ligand, which resulted in the formation of a very unstable platinum(IV) intermediate.