α-Substituted Alkenyl and α-Disubstituted Alkylidene Complexes with the OsCl(CO)(PiPr3)2 Skeleton

Complex Os(η2-PhC⋮CPh)(CO)(PiPr3)2 (1) reacts with 1 equiv of HBF4 to give the hydride species [OsH(η2-PhC⋮CPh)(CO)(PiPr3)2]BF4 (2), which affords the α-substituted alkenyl compound Os{(E)-C(Ph)CHPh}Cl(CO)(PiPr3)2 (3) by treatment with NaCl. Complex 3 reacts with Brønsted acids to give α-disubstituted alkylidene derivatives. Thus, the reaction with 1 equiv of HBF4 yields the cationic complex [OsCl{C(Ph)CH2Ph}(CO)(PiPr3)2][BF4] (4). The treatment of 3 with 1 equiv of HCl gives the neutral alkylidene derivative OsCl2{C(Ph)CH2Ph}(CO)(PiPr3)2 (5), while the reaction with an excess of HCl yields the anionic alkylidene complex [HPiPr3][OsCl3{C(Ph)CH2Ph}(CO)(PiPr3)] (6).