Dimethylplatinum(IV) Complexes With Cyanide: Thermal and Photoassisted Substitution Reactions, and Characterization of Products by N.M.R.

Abstract

Reactions of cyanide with the dimethylplatinum (IV) complexes, [PtMe₂(OH) (H₂0)_{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 J_{pt -C} and δ_C of the cyanide ligands have been evaluated.