Alkylidene and Vinylidene “Pincer” Complexes from Reactions of Alkynes with Ruthenium and Osmium Hydrides

Reactions of 1-pentyne and tert -butylacetylene with RuHCl[1,3-(CH 2 PBu t 2 ) 2 C 6 H 4 ] and OsH 2 Cl(PCP) (PCP = [2,6-(CH 2 PBu t 2 ) 2 C 6 H 3 ] - ) afforded the square-pyramidal 16-electron alkylidene and vinylidene complexes RuCl( C(Me)Pr)(PCP) ( 1 ), RuCl( C CHBu t )[1-(C CHBu t )-2,6-(CH 2 PBu t 2 ) 2 C 6 H 3 ] ( 2 ), OsCl( C CHPr)(PCP) ( 3 ), and OsCl( C CHBu t )(PCP) ( 4 ). These reactions were studied in solution by NMR spectroscopy. The structures of 1 − 4 were determined by X-ray crystallography.