Syntheses, structures and vibrational spectra of some dimethyl sulfoxide solvates of bismuth(III) bromide and iodide

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)over bar>, a 8.467(4), b 9.109(4), c 13.901(4) Angstrom, alpha 76.34(4), beta 76.95(4), gamma 64.56(4)degrees, Z = 2; conventional R on \F\ was 0.050 for N-o 2306 independent 'observed' (I > 3 sigma(I)) reflections. The complex is mononuclear with a quasi-octahedral fac-bismuth environment, [(dmso-O3BiBr3], isomorphous with the previously determined chloride. Orange BiI3.2dmso is triclinic, <P(1)over bar>, a 12.558(2), b 8.962(2), c 8.342(1) Angstrom, alpha 61.85(1), beta 78.27(1), gamma 76.89(2)degrees, 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)(2)I2Bi(mu-I)(2)BiI2(O-dmso)(2)]; the two O-dmso ligands about each six-coordinate bismuth lie trans. Red BiI3 . 22/3dmso is triclinic, <P(1)over bar>, a 16.435(6), b 14.926(2), c 12.396(3) Angstrom, alpha 74.89(2), beta 73.24(2), gamma 79.18(2)degrees, 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(mu-I)(3)BiI3](3-). Bands in the far-infrared and Raman spectra due to the nu(BiX) modes are assigned and discussed in relation to the structures of the complexes. The assignment of the nu(BiO) modes is discussed.