Reactions and properties of some trimethyleneplatinum(IV) complexes

The ligands L in the compounds PtX2(C3H6)L2 (X = Cl, Br) are found to be replaced in the order, tetrahydrofuran, pyridine, 4-methylpyridine, ethylenediamine, without displacement of the trimethylene moiety. A dimethylformamide derivative of trimethyleneplatinum(IV) was also prepared, but dimethyl sulphoxide and olefins (ethylene, cyclooctadiene) displace the C3H6 under some conditions. No reaction with triphenylphosphine, arsine and stibine in DMSO and DMF occurs if L2 = ethylenediamine or 2.2′-bipyridine, but when L = C5H5N or 4-CH3C5H4N, reductive elimination occurs with evolution of cyclopropane. The yield of gas depends, however, on the nature of L, X and the entering ligand, due to the parallel formation of coloured products, in which the platinum trimethylene ring is intact, under some conditions. The kinetics of the cyclopropane displacement have been studied and a mechanism involving ionic intermediates is proposed.