COORDINATION-COMPLEXES OF THE BISMUTH(III) THIOLATE BI(SC6F5)(3)

The reaction between Bi(SC6F5)(3) 1 and SPPh(3) afforded crystals of [Bi(SC6F5)(3)(SPPh(3))] 5 which was characterised by X-ray crystallography. Complex 5 contains a bismuth centre bonded to three SC6F5 groups and the sulfur atom of a SPPh(3) ligand such that the co-ordination geometry is disphenoidal with the SPPh(3) ligand trans to one thiolate group. An additional intermolecular interaction is also present due to a weakly bridging thiolate sulfur which results in a centrosymmetric dimer with each bismuth centre having square-based pyramidal five-co-ordination. A similar structure was observed for the anion in the ionic complex [K(18-crown-6)][Bi(SC6F5)(3)(NCS)] 6 (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane) derived from the reaction between 1 and [K(18-crown-6)]SCN. The anion [Bi(SC6F5)(3)(NCS)](-) has a disphenoidal geometry with an axial thiolate and N-bonded thiocyanate ligand which also bridges between two centrosymmetrically related bismuth centres giving a structure similar to 5. The reaction between 1 and either OPPh(3), hmpa (hexamethylphosphoramide) or dmpu (N,N'-dimethylpropyleneurea) afforded the bis(ligand) complexes [Bi(SC6F5)(3)(OPPh(3))(2)].CH2Cl2 8, [Bi(SC6F5)(3)(hmpa)(2)] 9 and [Bi(SC6F5)(3)(dmpu)(2)] 10 respectively all of which were characterised by X-ray crystallography. The structures of 8-10 are all similar in being monomeric and having a five-co-ordinate, square-based pyramidal geometry around the bismuth centre with one thiolate in the apical site and the two ligands in a cis configuration in the basal plane each trans to a basal thiolate. The reaction between 1 and N,N'-dimethylthiourea. S=C(MHMe)(2), afforded the tris(ligand) complex [Bi(SC6F5)(3){S=C(NHMe)(2)}(3)] 11. An X-ray crystallographic study revealed a six-co-ordinate complex with a geometry close to that of a regular octahedron with the three thiolates and three thiourea ligands both having fac configurations. The structures are discussed in terms of the SC6F5 group having properties analogous to chloride, and hence being a pseudohalide, and also in terms of ligand co-ordination occuring through the thiolate Bi-S sigma(+) orbitals.