STRUCTURAL STUDIES ON PHENYL BISMUTH HALIDES AND HALOGENOANIONS

Structural studies by X-ray crystallography have been carried out for a range of phenyl bismuth halides and halogenoanions. The complexes [BiPhBr2(thf)] 1 and [BiPhI2(thf)] 2 (thf = tetrahydrofuran) form one-dimensional polymeric chains with a single asymmetrically-bridging halide between each pair of adjacent bismuth atoms. The co-ordination geometry around the bismuth centre is that of a square-based pyramid with the phenyl group in the apical position and two cis halides, a bridging halide from an adjacent monomer unit and a thf ligand in the basal plane. Addition of [NEt4]I to 2 affords the ionic species [NEt4]2[Bi2Ph2I6].Et2O 3 which contains the discrete dimeric [Bi2Ph2I6]2- anion. This anion comprises two edge-shared square-based pyramids with an angle of 105.2-degrees between the basal planes. As with 1 and 2, the phenyl group occupies the apical site with the basal sites around each bismuth occupied by two terminal and two bridging iodides. The complex [BiPh2Br(thf)] 5 is monomeric and has an equatorially vacant trigonal-bipyramidal co-ordination geometry around the bismuth centre in which the phenyl groups occupy the equatorial sites and the bromine and thf ligand the axial sites. The structure of [PPh4][BiPh2Br2] 6 contains monomeric [BiPh2Br2]- anions with a geometry similar to that found in 5. Comparisons are made, where appropriate, with related tellurium(IV) compounds, and the nature of the bonding in the complexes is discussed particularly with regard to the details of the secondary, intermolecular bonds observed in the structures of 1-3.