Crystal structures and vibrational spectra of tetrahalogenoacetylacetonatoosmates(IV), [OsX4(acac)]-, X = Cl, Br, I

Article abstract of DOI:10.1002/zaac.19976231226

By reaction of the hexahalogenoosmates(IV) with acetylacetone the tetrahalogenoacetylacetonatoosmates(IV) [OsX₄(acac)]^- (X = Cl, Br, I) are formed, which have been purified by chromatography and precipitated from aqueous solution as tetraphenylphosphonium (Ph₄P) or cesium salts. X-ray structure determinations on single crystals have been performed of (Ph₄P)[OsCl₄(acac)] (1) (triclinic, space group P1, a = 9.9661(6), b = 11.208(2), c = 13.4943(7) A, α = 101.130(9), β = 91.948(6), γ = 96.348(8)°, Ζ = 2), (Ph₄P)[OsBr₄(acac)] (2) (monoclinic, space group P2₁/n, a = 9.0251(8), b = 12.423(2), c = 27.834(2) A, β = 94.259(7)°, Ζ = 4) and (Ph₄P)[OsI₄(acac)] (3) (monoclinic, space group P2₁/c, a = 18.294(3), b = 10.664(2), c = 18.333(3) A. β = 117.68(2)°, Ζ = 4). Due to the increasing trans influence in the series O < Cl < Br < I the Os-O^? distances of O^?-Cl-X′ axes are lengthened and the OsO^? stretching vibrations are shifted to lower frequencies. The Os-X′ bond lenghts are shorter as compared with symmetrically coordinated X-Os-X axes.