DIMETHYLSULFOXIDE SOLVATES OF BISMUTH(III) IODIDE. Brian W. Skelton, Peter C. Junk and Allan H. White, Department of Chemistry, University of Western Australia, Nedlands, Western Australia 6907, Australia

At room temperature, bismuth(III) iodide crystallises from solutions of dimethylsulfoxide (dmso) in at least two substantial, well-defined crystalline solvates, BiI₃.2dmso (orange) and BiI₃.8/3dmso (red). BiI₃.2dmso is triclinic P , a 12.558(2), b 8.962(2), c 8.342(1)Å, ( 61.85(1), ( 78.27(1), ( 76.89(2)( Z=2, conventional R on |F| being 0.048 for N_O 1953 independent `observed' reflections. The complex is a centrosymmetric binuclear array, one dimer in the unit cell: [(O-dmso)<sub>2</sub>I<sub>2</sub>Bi((-I)<sub>2</sub>BiI<sub>2</sub>(O/i>-dmso)<sub>2</sub>], bismuth atoms being six-coordinate with the dmso oxygen atoms trans. Bi-O are 2.37(2),2.41(2), Bi-I(terminal) 2.941(7),2.922(9) and Bi-I(bridging) 3.211(7),3.25(1)Å. Bi-O-S are 123.9(7),125.8(7) and Bi-I-Bi 96.03(7)(. The badly-twinned crystals of BiI<sub>3</sub>.8/3dmso are also triclinic P , a 16.435(6), b 14.926(2), c 12.396(3)Å, ( 74.89(2), ( 73.24(2), ( 79.18(2)(, Z=6, R 0.059 for N<sub>O</sub> 5858. The complex is [Bi(O-dmso)<sub>8</sub>]<sup>3+</sup>[I<sub>3</sub>Bi((-I)<sub>3</sub>BiIsub>3]<sup>3-</sup> (i.e. [Bi<sub>2</sub>I<sub>9</sub>]<sup>3-</sup> ) the bismuth environment of the novel cation being, unusually, dodecahedral rather than square anti-prismatic, the `inner' sites of the trapezoidal planes having perhaps slightly longer Bi-O (2.41(2)-2.49(2)Å) than the peripheral (2.36(2)-2.44(2)Å). In the anion, Bi-I(bridging) are 3.152(2)-3.337(3) and Bi-I(terminal) 2.903(3)-3.012(2)Å. In the cation, half of the ligand sulfur atoms are disordered in the usual way; for the more precisely determined ordered species, Bi-O-S are 118.8(9)-131(1)(.