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    Reactivity of the imine-vinylidene complexes OsCl2(=C=CHPh)(NH=CR2) (PiPr3)2 [CR2 = CMe2, C(CH2)4CH2]

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    The reactivity of the imine-vinylidene compounds OsCl2(=C=CHPh)(NH=CR2) (PiPr3)2 [CR2 = CMe2 (1), C(CH2)4CH2 (2)] toward amines, nBuLi, and HBF4 has been studied. Complexes 1 and 2 react with triethylamine and diallylamine to give equilibrium mixtures of the corresponding starting materials and the five-coordinate azavinylidene derivatives OsCl(=N=CR2)(=C=CHPh)(PiPr3)2 [CR2 = CMe2 (3), C(CH2)4CH2 (4)], which are obtained as pure microcrystalline solids by reaction of 1 and 2 with nBuLi. The structure of 3 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 phophines and inequivalent angles within the Y-shaped equatorial plane. The azavinylidene group coordinates in a bent fashion with an Os-N-C angle of 157.2(6)°. Complexes 1 and 2 also react with allylamine and aniline. The reactions initially give 3 and 4. However, the amount of these compounds decreases by increasing the reaction time. This decrease is accompanied with the formation of mixed amine-phosphine compounds OsCl2(=C=CHPh)(NH=CR2)(NH2R′) (PiPr3) [R′ = allyl; CR2 = CMe2 (5), C(CH2)4CH2, (6). R′ = Ph; CR2 = CMe2 (7), C(CH2)4CH2 (8)]. The structure of 5 in the solid state has been also determined by an X-ray diffraction study. In this case, the geometry around the osmium atom can be rationalized as a distorted octahedron with the amine and phosphine ligands mutually trans disposed and the chlorine ligands mutually cis disposed. The X-ray analysis also shows that the NH-hydrogen atoms of the amine and the chlorines are involved in intra- and intermolecular H⋯Cl hydrogen bonding. The reactions of 1 and 2 with HBF4·OEt2 afford the carbyne derivatives [OsCl2(≡CCH2Ph)(NH=CR2) (PiPr3)2][BF4] [CR2 = CMe2 (9), C(CH2)4CH2 (10)]. Both 1 and 2 lose the imine ligand to give OsCl2(=C=CHPh)(PiPr3)2 (11) in toluene under reflux.Financial support from the DGES of Spain (Project PB98-1591) is acknowledged. R.C. thanks the “Ministerio de Ciencia y Tecnología” for a grant.Peer Reviewe
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