Displacement of norbornadiene (NBD) from PtMe₂(NBD) BY N-donors, dimethylsulfoxide, and cyanide, and reactions of cis-PtMe₂L₂ iodomethane

Norbornadiene (NBD) was displaced from PtMe₂(NBD) by a range of ligands L to form cis-PtMe₂L₂ (L = pyridine (py), NH₃, dimethylsulfoxide (DMSO); L₂ = 2,2′-bipyridyl (bipy), ethylenediamine (en), N,N,N′,N′-tetramethylethylenediamine (tmen) - but not L = acetonitrile, benzonitrile, N, N-dimethylformamide, or water). These reactions occur more readily than the corresponding displacements of 1,5-cyclooctadiene (COD) from PtMe₂(COD). Cyanide readily displaced the diolefin from either PtMe₂(NBD) or PtMe₂(COD) to form cis-PtMe₂CN)₂^2-, but no reaction occurred with bromide, chloride, and acetylacetonate. Thiocyanate and iodide slowly reacted, but no methyl-platinum product was obtained. The reaction of each of the compounds PtMe₂L₂ with MeI was studied in benzene. PtMe₂(NBD) gave [PtMe₃I]₄. With L = py, 1 2(bipy), or 1 2(tmen), PtMe₃IL₂ was obtained rapidly at room temperature. For the sparingly soluble compounds with L = NH₃ or 1 2(en), heating was necessary for reaction. The product from PtMe₂(en) was PtMe₃I(en), but cis-PtMe₂(NH₃)₂ gave a mixture of [PtMe₃(NH₃)(μ-I)]₂ and fac-[PtMe₃(NH₃)₃]I. With L = DMSO, heating initially gave PtMe₃I(DMSO)₂, which slowly lost DMSO to form [PtMe₃I]₄. For L = py, 1 2(tmen), treatment with acid readily removed L from PtMe₃IL₂.