Formation of Imine−Vinylidene−Osmium(II) Derivatives by Hydrogen Transfer from Alkenyl Ligands to Azavinylidene Groups in Alkenyl−Azavinylidene−Osmium(IV) Complexes

Abstract

Treatment at room temperature of the hydride−azavinylidene complexes OsHCl2(NCR2)(PiPr3)2 [CR2 = CMe2 (1), (2)] with Ag[CF3SO3] and the subsequent addition at −25 °C of phenylacetylene to the resulting solutions affords the alkenyl−azavinylidene derivatives [Os{(E)-CHCHPh}Cl(NCR2)(PiPr3)2][CF3SO3] [CR2 = CMe2 (3), (4)], where the Hβ atoms of the alkenyl ligands interact with the osmium atoms to form agostic bonds. The addition at −30 °C of NaCl to tetrahydrofuran solutions of 3 and 4 produces the split of the agostic interactions and the formation of the neutral six-coordinate alkenyl−azavinylidene compounds Os{(E)-CHCHPh}Cl2(NCR2)(PiPr3)2 [CR2 = CMe2 (5), (6)]. In dichloromethane at room temperature complexes 5 and 6 evolve into the imine−vinylidene derivatives OsCl2(CCHPh)(NHCR2)(PiPr3)2 [CR2 = CMe2 (7), (8)], as a result of the hydrogen transfer from the styryl ligands to the azavinylidene groups. The structure of 7 in the solid state has been determined by an X-ray diffraction study. The geometry arou...