Dimethylplatinum(Iv) complexes with cyanide: Thermal and photoassisted substitution reactions, and characterization of products by N.M.R.

Reactions of cyanide with the dimethylplatinum(Iv) complexes, [PtMe2(OH)2(H2O)1·5]n, [PtMe2Br2]n and fac-PtMe2Br(H2O)3 +, have been studied, principally by 1H, 13C and 195Pt n.m.r. Cyanide rapidly displaces the ligands trans to the methyl groups. Subsequent reactions cis to the methyl groups occur more slowly with heating, or, for bromo complexes, on ultraviolet irradiation. These substitution reactions compete with reductive elimination of groups from the platinum(IV) compounds to produce platinum(II) products. All attempts to prepare solutions of fac-PtMe2(CN)(H2O)3 + were unsuccessful. Oxidative addition of ICN to cis-PtMe2(py)2 (py = pyridine) gave PtMe2I(CN)(py)2, from which a solution of fac-PtMe2(CN)(MeOH)3 + in methanol could be obtained. Addition of water or aqueous acid to this solution gave a very insoluble precipitate of [PtMe2(CN)(OH)]n The cis and trans influences on 1Jpt-C and δ C of the cyanide ligands have been evaluated