Reactivity of the Imine−Vinylidene Complexes\nOsCl₂(CCHPh)(NHCR₂)(PⁱPr₃)₂ [CR₂ = CMe₂,\nC(CH₂)₄CH₂]^†

Abstract

The reactivity of the imine−vinylidene compounds OsCl₂(CCHPh)(NHCR₂)(PⁱPr₃)₂\n[CR₂ = CMe₂ (<b>1</b>), (<b>2</b>)] toward amines, ⁿBuLi, and HBF₄ has been studied.\nComplexes <b>1</b> and <b>2</b> react with triethylamine and diallylamine to give equilibrium mixtures\nof the corresponding starting materials and the five-coordinate azavinylidene derivatives\nOsCl(NCR₂)(CCHPh)(PⁱPr₃)₂ [CR₂ = CMe₂ (<b>3</b>), (<b>4</b>)], which are obtained\nas pure microcrystalline solids by reaction of <b>1</b> and <b>2</b> with ⁿBuLi. The structure of <b>3</b> in the\nsolid state has been determined by an X-ray diffraction study. The geometry around the\nmetal center could be described as a distorted trigonal bipyramid with apical phophines\nand inequivalent angles within the Y-shaped equatorial plane. The azavinylidene group\ncoordinates in a bent fashion with an Os−N−C angle of 157.2(6)°. Complexes <b>1</b> and <b>2</b> also\nreact with allylamine and aniline. The reactions initially give <b>3</b> and <b>4</b>. However, the amount\nof these compounds decreases by increasing the reaction time. This decrease is accompanied\nwith the formation of mixed amine−phosphine compounds OsCl₂(CCHPh)(NHCR₂)(NH₂R‘)(PⁱPr₃) [R‘ = allyl; CR₂ = CMe₂ (<b>5</b>), (<b>6</b>). R‘ = Ph; CR₂ = CMe₂ (<b>7</b>),\n (<b>8</b>)]. The structure of <b>5</b> in the solid state has been also determined by an X-ray\ndiffraction study. In this case, the geometry around the osmium atom can be rationalized\nas a distorted octahedron with the amine and phosphine ligands mutually trans disposed\nand 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\nH···Cl hydrogen bonding. The reactions of <b>1</b> and <b>2</b> with HBF₄·OEt₂ afford the carbyne\nderivatives [OsCl₂(⋮CCH₂Ph)(NHCR₂)(PⁱPr₃)₂][BF₄] [CR₂ = CMe₂ (<b>9</b>), (<b>10</b>)].\nBoth <b>1</b> and <b>2</b> lose the imine ligand to give OsCl₂(CCHPh)(PⁱPr₃)₂ (<b>11</b>) in toluene under\nreflux.