Co-ordination complexes of the bismuth(III) thiolate Bi(SC6F5)3

Abstract

The reaction between Bi(SC₆F₅)₃1 and SPPh₃ afforded crystals of [Bi(SC₆F₅)₃(SPPh₃)]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 SPPh₃ ligand such that the co-ordination geometry is disphenoidal with the SPPh₃ 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 OPPh₃, hmpa (hexamethylphosphoramide) or dmpu (N,N′-dimethylpropyleneurea) afforded the bis(ligand) complexes [Bi(SC₆F₅)₃(OPPh₃)₂]·CH₂Cl₂8, [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, SC(NHMe)_2′ afforded the tris(ligand) complex [Bi(SC₆F₅)₃{SC(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 σ* orbitals.