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 crystallogra phy. 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 ge ometry is disphenoidal with the SPPh(3) ligand trans to one thiolate g roup. An additional intermolecular interaction is also present due to a weakly bridging thiolate sulfur which results in a centrosymmetric d imer with each bismuth centre having square-based pyramidal five-co-or dination. 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 g iving a structure similar to 5. The reaction between 1 and either OPPh (3), hmpa (hexamethylphosphoramide) or dmpu (N,N'-dimethylpropyleneure a) afforded the bis(ligand) complexes [Bi(SC6F5)(3)(OPPh(3))(2)].CH2Cl 2 8, [Bi(SC6F5)(3)(hmpa)(2)] 9 and [Bi(SC6F5)(3)(dmpu)(2)] 10 respecti vely all of which were characterised by X-ray crystallography. The str uctures of 8-10 are all similar in being monomeric and having a five-c o-ordinate, square-based pyramidal geometry around the bismuth centre with one thiolate in the apical site and the two ligands in a cis conf iguration in the basal plane each trans to a basal thiolate. The react ion between 1 and N,N'-dimethylthiourea. S=C(MHMe)(2), afforded the tr is(ligand) complex [Bi(SC6F5)(3){S=C(NHMe)(2)}(3)] 11. An X-ray crysta llographic study revealed a six-co-ordinate complex with a geometry cl ose to that of a regular octahedron with the three thiolates and three thiourea ligands both having fac configurations. The structures are d iscussed in terms of the SC6F5 group having properties analogous to ch loride, and hence being a pseudohalide, and also in terms of ligand co -ordination occuring through the thiolate Bi-S sigma(+) orbitals.