The reaction of N,N′-di-tert-butylthiourea (dtbtu) with antimony(III) halides - Formation of the triply bridged [(dtbtu)SbX2(μ-X) 2(μ-dtbtu)-SbX2(dtbtu)] (X = Cl, Br) dimers

The reactions of N,N′-di-tert-butylthiourea (dtbtu) with SbX 3 (X = Cl, Br) in a 2:1 dtbtu/SbX3 ratio unexpectedly lead to products with a 3:2 dtbtu/SbX3 ratio. These complexes have been shown by X-ray crystallographic studies to exist as triply bridged dimers, [(dtbtu)SbX2(μ-X)2(μ-dtbtu)SbX2(dtbtu)], (X = Cl, 1; X = Br, 2), which feature one bridging dtbtu ligand and two bridging halides. The geometry at antimony is highly distorted octahedral. This distortion is partly due to the bridging ligands, but there is also evidence for the presence of stereochemically active lone pairs. In 1 the lone pair appears to be located towards an edge of the octahedron between a terminal and a bridging halide. The situation is similar in 2, but the distortion is considerably greater at one of the antimony atoms than at the other. In contrast, the reaction of dtbtu with SbI3 yields a 1:1 complex, [SbI3(dtbtu)] (3), which is likely to be polymeric with bridging iodide ligands. The low solubility of the iodide complex has precluded characterisation by X-ray crystallography. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.