One-Pot Synthesis for Osmium(II) Azavinylidene−Carbyne and Azavinylidene−Alkenylcarbyne Complexes Starting from an Osmium(II) Hydride−Azavinylidene Compound

Treatment at room temperature of the complex OsHCl 2 ( N CMe 2 )(P i Pr 3 ) 2 ( 1 ) with Ag[CF 3 SO 3 ] and the subsequent stirring of the resulting solution under an acetylene atmosphere gives the azavinylidene−carbyne derivative [OsCl( N CMe 2 )(⋮CCH 3 )(P i Pr 3 ) 2 ][CF 3 SO 3 ] ( 2 ). The related complexes [OsCl( N CMe 2 )(⋮CCH 2 R)(P i Pr 3 ) 2 ][CF 3 SO 3 ] (R = Cy ( 3 ), (CH 2 ) 2 CH 3 ( 4 )) have been prepared by reaction of 1 with Ag[CF 3 SO 3 ] and cyclohexylacetylene or 1-pentyne. The structure of 2 in the solid state has been determined by an X-ray diffraction study. The geometry around the metal center could be described as a distorted trigonal bipyramid with apical phosphines and inequivalent angles within the Y-shaped equatorial plane. The azavinylidene coordinates in a bent fashion with an Os−N−C angle of 152.0(8)°. Complexes 2 − 4 react with MeLi to afford the five-coordinate azavinylidene−vinylidenes OsCl( N CMe 2 )( C CHR)(P i Pr 3 ) 2 (R = H ( 5 ), Cy ( 6 ), (CH 2 ) 2 CH 3 ( 7 )), as a result of the deprotonation of the β -CH 2 group of the carbyne ligands in 2 − 4 . The formation of 2 − 4 involves azavinylidene−alkenyl and imine−vinylidene intermediates. In agreement with this, it is also reported that, at −25 °C, the addition of cyclohexylacetylene to the solution resulting from the treatment of 1 with Ag[CF 3 SO 3 ] affords [Os{( E )-CH CHCy}Cl( N CMe 2 )(P i Pr 3 ) 2 ][CF 3 SO 3 ] ( 8 ), where the H β atom of the alkenyl ligand interacts with the osmium atom to form an agostic bond. At −30 °C, the addition of NaCl to tetrahydrofuran solutions of 8 gives OsCl 2 ( C CHCy)(NH CMe 2 )(P i Pr 3 ) 2 ( 9 ), which evolves into 6 in solution at room temperature. Complex 1 also reacts with Ag[CF 3 SO 3 ] and 2-methyl-1-buten-3-yne. The reaction leads to the azavinylidene−alkenylcarbyne [OsCl( N CMe 2 )(⋮CCH CMe 2 )(P i Pr 3 ) 2 ][CF 3 SO 3 ] ( 10 ), which by deprotonation with MeLi yields the azavinylidene−alkenylvinylidene OsCl( N CMe 2 ){ C CHC(Me) CH 2 }(P i Pr 3 ) 2 ( 11 ). The formation of 10 proceeds similarly to those of 2 − 4 . Thus, it has been observed that, at −25 °C, the addition of 2-methyl-1-buten-3-yne to the solution resulting from the treatment of 1 with Ag[CF 3 SO 3 ] gives [Os{( E )-CH CHC(Me) CMe 2 }Cl( N CMe 2 )(P i Pr 3 ) 2 ][CF 3 SO 3 ] ( 12 ), which in solution at room temperature evolves into 10 . The complexes [OsCl( N CMe 2 )(⋮CCH CPhR)(P i Pr 3 ) 2 ][CF 3 SO 3 ] (R = H ( 13 ), CH 3 ( 14 ), Ph ( 15 )) have been prepared by reaction of 1 with Ag[CF 3 SO 3 ] and 1-phenyl-2-propyn-1-ol, 2-phenyl-3-butyn-2-ol, and 1,1-diphenyl-2-propyn-1-ol, respectively. The deprotonation of 14 with MeLi affords OsCl( N CMe 2 ){ C CHC(Ph) CH 2 }(P i Pr 3 ) 2 ( 15 ).