The reactions of SbX3 (X = Cl, Br, I) with N-methylbenzothiazole-2-thione (mbtt) and N-methylbenzothiazole-2-selone (mbts). Formation of the mixed mer/fac-complex [mer-SbBr3(mbts)2(μ-mbts)fac-SbBr3(mbts)2]·CH2Cl2

The reactions of the antimony(III) halides, SbX3 (X = Cl, Br, I) with the heterocyclic thione, N-methylbenzothiazole-2-thione (mbtt) and the analogous selone, N-methylbenzothiazole-2-selone (mbts) are reported. The products formed are highly dependent upon the identity of the halide, and in one case on the identity of the chalcogen donor atom. The reaction of SbCl3 with both mbtt and mbts (and the reaction of SbBr3 with mbtt), forms complexes in CH2Cl2 with a 2:1 ligand to metal ratio, [SbX3(L)(μ-L)2SbX3(L)]·CH2Cl2, [X = Cl, L = mbtt (1), L = mbts (2); X = Br, L = mbtt (3)]. These complexes are weakly held together, and feature a primary pyramidal SbX3 coordination sphere with weak secondary donor-acceptor bonding to the chalcone donor ligands, giving an overall [3+3] octahedral geometry around each antimony atom. In contrast, the reaction of SbBr3 with mbts in CH2Cl2 produces a highly unusual 5:2 ligand:SbBr3 complex, [mer-SbBr3(mbts)2(-mbts)fac-SbBr3(mbts)2]·CH2Cl2 (4). The fac-substituted antimony center has a [4+2] bonding arrangement, consisting of a primary [SbBr3(mbts)] coordination sphere and weaker secondary bonds to two further mbts ligands. In contrast, the bonding at the mer-substituted antimony atom is better described as [5+1], with a primary [SbBr3(mbts)2] coordination sphere and only one secondary bond to another mbts ligand. The complex is highly unusual in featuring two antimony atoms with different primary/secondary coordination spheres in the same complex. The reactions of mbtt and mbts with SbI3 result in the formation of 1:1 complexes [SbI3L], which display chain polymeric structures, {[SbI2(mbtt)(μ-I)]}n (5) and {[SbI2(mbts)(μ-I)]}n (6). The complexes consist of see-saw [SbI3L] units linked into polymeric chains by bridging iodine atoms, the antimony atoms thus exhibits a square pyramidal geometry. The iodide complexes feature a stereochemically active lone pair trans to the apical iodine atom, and feature much shorter antimony-chalcogen bonds than observed for 1-4. © 2010 Elsevier Ltd. All rights reserved.