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

Autores: Ricardo Castarlenas, Miguel A. Esteruelas, Enrique Gutiérrez-Puebla y Enrique Oñate Ref. revista: Organometallics, 20, 1545-1554, (2001)

The reactivity of the imine-vinylidene compounds OsCl2(dCdCHPh)(NHdCR2)(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(dNdCR2)(dCdCHPh)(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(dCdCHPh)(NHdCR2)(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 NHhydrogen atoms of the amine and the chlorines are involved in intra- and intermolecular H...Cl hydrogen bonding. The reactions of 1 and 2 with HBF4âOEt2 afford the carbyne derivatives [OsCl2(tCCH2Ph)(NHdCR2)(PiPr3)2][BF4] [CR2 ) CMe2 (9), C(CH2)4CH2 (10)].
Both 1 and 2 lose the imine ligand to give OsCl2(dCdCHPh)(PiPr3)2 (11) in toluene under reflux.