Vinylidene transition-metal complexes, 50 - Carbynehydrido- and vinylidenehydridoosmium complexes with Os(PCy3)(2) as a molecular unit

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