Stability and reactivity of the cis-Pt-II(R)(alkyne) fragment (R equals alkyl): An unprecedented rearrangement to form the Pt-II(eta(3)-allyl) moiety

The complexes [PtR(eta(2)-E-MeO2CCH=CHCO2Me)(phen)](+) BF4- (R = Me 1a or Et 1b; phen = 1,10-phenanthroline) reacted with alkynes yielding the corresponding products [PtR(eta(2)-alkyne)(phen)]+BF4- 2. These can be isolated in the case of disubstituted electron-rich alkynes, while the electron-poor MeO2CC equivalent to CCO2Me inserted into the Pt-R bond leading to the corresponding sigma-vinyl derivative. Type 2 complexes containing alk-1-ynes undergo an unprecedented rearrangement to form stable [Pt(eta(3)-allyl)(phen)]+BF4- products. Mechanistic aspects of the reaction are discussed.