Reactions of an osmium-elongated dihydrogen complex with terminal alkynes:: Formation of novel bifunctional compounds with amphoteric nature

The trihydride complex OsH3{C6H4C(O)CH3}((PPr3)-Pr-i)(2) (1) reacts with (HBF4H2O)-H-. to give the elongated dihydrogen derivative [Os{C6H4C(O)CH3](eta(2)-H-2)(H2O)((PPr3)-Pr-i)(2)]BF4 (2), with a separation between the hydrogen atoms of the elongated dihydrogen of 1.35 Angstrom. The addition of acetone oxime to dichloromethane solutions of 2 produces the substitution of the water ligand by the oxime and the formation of Os{C6H4C(O)CH3}(eta(2)-H-2){N(OH)=C(CH3)(2)}((PPr3)-Pr-i)(2)]BF4 (3), which shows a hydrogen -hydrogen distance of 1.34 1. Complex 3 reacts with phenylacetylene, cyclohexylacetylene, and tert-butylacetylene to give acetophenone and the oximate-carbyne derivatives [OsH{K-N,K-O[ON=C(CH3)(2)]}(equivalent toCCH(2)R)((PPr3)-Pr-i)(2)] BF4 (R =Ph (4), Cy (5), Bu-t (6)). The structure of 4 has been determined by X-ray diffraction analysis. The distribution of ligands around the osmium atom can be described as a distorted trigonal bipyramid with apical phosphines and inequivalent angles within the Y-shaped equatorial plane. Complexes 4-6 have amphoteric nature, reacting with both KOH and HBF4(.)Et(2)O, The reactions with KOH afford the vinylidene derivatives OsH{K-N,K-O[ON=C(CH3)(2)]}(=C=CHR)((PPr3)-Pr-i)(2) (R = Ph (7), Cy (8), tBu (9)), whereas the reactions with (HBF4Et2O)-Et-. give the fluoro-oxime compounds [6sH[F --- HO =C(CH3)(2)]}(equivalent toCCH(2)R)((PPr3)-Pr-i)(2)]BF4 (R = Ph (10), Cy (11), tBu (12)). The structures of 7 and 11 have been determined by X-ray diffraction analysis. The distribution of ligands around the osmium atom of 7 is like that of 4, whereas the geometry around the metallic center of 11 can be rationalized as a distorted octahedron with the phosphine ligands in trans positions. Complexes 10, 11, and 12 contain a strong intramolecular F- - -H hydrogen bond between the fluorine and the OH-hydrogen atom of the oxime in the solid state and in dichloromethane solution (J(H-F) = 67.5 (10), 68.1 (11), and 68.7 (12) Hz). The formation of 4-12 is also discussed, on the basis of deuterium label experiments.