Carbynehydrido- and Vinylidenehydridoosmium Complexes with Os(PCy3)2 as a Molecular Unit

The reaction of OsCl3·2H2O with PCy3 leads under reducing conditions either to [OsH6(PCy3)2] (1) or [OsH2Cl2(PCy3)2] (2). Treatment of 2 with terminal alkynes HC≡CR (R = Ph, SiMe3) affords the carbynehydrido complexes [OsHCl2(≡CCH2R)(PCy3)2] (4, 5), of which 5 (R = SiMe3) is easily converted with traces of water into [OsHCl2(≡CCH3)(PCy3)2] (6). Compound 4 (R = Ph) reacts with NaOMe to yield the vinylidenehydridoosmium(II) complex [OsHCl(=C=CHPh)(PCy3)2] (7) which upon treatment with HBF4/OEt2 gives the five-coordinate cationic species [OsHCl(≡CCH2Ph)(PCy3)2]-BF4 (8). The reaction of [OsH3Cl(PCy3)2] (9) with HC≡CC(CH3)2Cl affords a mixture of [OsHCl2(≡CCH=CMe2)(PCy3)2] (10) and [OsCl2(H2)(=CHCH=CMe2)(PCy3)2] (11). Compound 11 is quite labile and by elimination of H2 gives 10. The molecular structure of 10 has been determined by X-ray crystallography.