Syntheses, Structures and Vibrational Spectra of Some Dimethyl Sulfoxide Solvates of Bismuth(III) Bromide and Iodide

Abstract

Room-temperature single-crystal X-ray studies are recorded for some dimethyl sulfoxide (dmso) solvates of bismuth(III) bromide and iodide. Colourless BiBr₃.3dmso is triclinic, P^-1, a 8·467(4), b 9·109(4), c 13·901(4) Å, α 76·34(4), β 76·95(4), γ 64·56(4)°, Z = 2; conventional R on |F| was 0·050 for N_o 2306 independent ‘observed’ (I > 3σ(I)) reflections. The complex is mononuclear with a quasi-octahedral fac-bismuth environment, [(dmso-O)₃BiBr₃], isomorphous with the previously determined chloride. Orange BiI₃-2dmso is triclinic, P^-1, a 12·558(2), b 8·962(2), c 8·342(1) Å, α 61·85(1), β 78·27(1), γ 76·89(2)°, Z = 2 f.u., R 0·048 for N_o 1953. The complex is binuclear, a pair of iodide atoms bridging the two bismuth atoms, [(dmso-O)₂I₂Bi(µ-I)₂BiI₂(O-dmso)₂]; the two O-dmso ligands about each six-coordinate bismuth lie trans. Red BiI₃.2 ⅔ dmso is triclinic, P^-1, a 16·435(6), b 14·926(2), c 12·396(3) Å, α 74·89(2), β 73·24(2), γ 79·18(2)°, Z = 6, R 0·059 for N_o 5858. The complex is [Bi(O-dmso)₈] [Bi₂I₉], the eight-coordinate metal environment of the cation being, unusually, dodecahedral; in the anion a pair of quasi-octahedral six-coordinate bismuth atoms are bridged by three iodides, [I₃Bi(µ-I)₃BiI₃]^3-. Bands in the far-infrared and Raman spectra due to the v(BiX) modes are assigned and discussed in relation to the structures of the complexes. The assignment of the v(BiO) modes is discussed.