Kristallstrukturen und Schwingungsspektren von Tetrahalogenoacetylacetonatoosmaten(IV), [OsX4(acac)]−, X  Cl,Br, I

Crystal Structures and Vibrational Spectra of Tetrahalogenoacetylacetonatoosmates(IV), OsX₄(acac)]^?, X ? Cl, Br, I 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) Å, α = 101.130(9), β = 91.948(6), γ = 96.348(8)°, Z = 2), (Ph₄P)OsBr₄(acac)] ( 2 ) (monoclinic, space group P2₁/n, a = 9.0251(8), b = 12.423(2), c = 27.834(2) Å, β = 94.259(7)°, Z = 4) and (Ph₄P)OsI₄(acac)] ( 3 ) (monoclinic, space group P2₁/c, a = 18.294(3), b = 10.664(2), c = 18.333(3) Å, β = 117.68(2)°, Z = 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.