Pyridine adducts of arylbismuth(III) halides

A range of bismuth trihalide and arylbismuth(III) halide complexes with pyr idine ligands has been prepared and structurally characterised. The complex [BiI3(py)(3)] (py = pyridine) is octahedral with the iodide and pyridine l igands arranged in a mer configuration. A seven-co-ordinate complex [BiCl3( py)(4)] is also described. The compounds [BiCl2Ph(4-Mepy)(2)] (4-Mepy = 4-m ethylpyridine), [BiBr2Ph(4-Mepy)(2)], [BiBr2Ph(4-Bu(t)py)(2)] (4-Bu(t)py = 4-tert-butylpyridine) and [BiI2Ph(4-Bu(t)py)(2)] all have a five-co-ordinat e, square-based pyramidal bismuth centre in which the phenyl group occupies the apical position with two trans halides and two trans pyridine ligands residing in the basal plane. In the solid state these moieties are dimerise d through a pair of weak asymmetric halide bridging interactions. The compl exes [BiBr2Ph(py)(2)] and [BiI2Ph(4-Mepy)(2)] have similar monomeric units but in the former case these are weakly associated into polymeric chains ra ther than dimers whereas, for the latter, dimers are formed through a singl e bridging iodide. In the structure of the ionic compound [4-Bu(t)pyH][BiCl 3Ph(4-Bu(t)py)] the [BiCl3Ph(4-Bu(t)py)](-) anion is monomeric with a squar e-based pyramidal structure in which the phenyl group is in an apical site whilst the three chlorides and 4-Bu(t)py ligand occupy the basal positions. An example of a diphenylbismuth halide complex is seen in the structure of [BiIPh2(4-Mepy)], the monomeric unit of which contains a four-co-ordinate bismuth centre with a geometry based on an equatorially vacant trigonal bip yramid in which the two phenyl groups are equatorial and the iodide and 4-m ethylpyridine ligand are axial. A weak association into polymeric chains oc curs through long Bi ... I interactions approximately trans to one phenyl g roup. All compounds are discussed in terms of their structure and bonding a nd compared with related materials previously characterised.