Evidence for platinum(II)-vinylidene complexes and their reactions with water to give hydrocarbons and olefins

Treatment of the alkynyl complexes trans-[Pt(Me)(C drop CR)(PPh3)(2)] (R = p-tolyl (la), Ph (Ib)) at low temperature in a CD2Cl2 solution with stoichiometric amounts of the acids HBF4Et2O or CF3SO3H affords the corresponding vinylidene derivatives trans-[Pt(Me) (=C=C(H)R) (PPh3)(2)]X (R = p-tolyl, X = BF4 (2aBF(4)); R = p-tolyl, X = CF3SO3 (2aCF(3)SO(3)); R = Ph, X = BF4 (2bBF(4))) on the basis of H-1- and P-31(H-1)-NMR data. The reactions of the in situ generated complexes 2 with water, which were followed by H-1- and P-31{H-1}-NMR, lead to the formation of a mixture of the carbonyl complex [Pt(Me)(CO)(PPh3)(2)]X (3) and the hydroxo-bridged dinuclear compound [Pt(mu-OH)(PPh3)(2)](2)X-2 (4) in a ca. 1:2 ratio. The formation of 3 and 4 is accompanied with the liberation of hydrocarbons R-CH, and olefins CH3CH=CHR (R = p-tolyl, Ph), respectively, which arise from the vinylidene ligand likely via an hydroxycarbene intermediate. (C) 1999 Elsevier Science S.A. All rights reserved.