Complexes of 2,5,7,9-tetrathiabicyclo[4.3.0]non-1(6)-ene-8-thione(L1). Part 1. Synthesis and antimony-121 Mössbauer spectroscopic characterisation of SbCl3(L1)1.5, crystal and molecular structures of SbCl3(L1)1.5 and uncomplexed L1

Abstract

The preparation, crystal structure, and Mössbauer spectroscopic studies of SbCl₃(L¹)_1.5 are reported {L¹= 2,5,7,9-tetrathiabicyclo[4.3.0]non-1(6)-ene-8-thione}. The structure is polymeric with each antimony centre bonded to three chlorine atoms [Sb–Cl 2.305(14), 2.385(13), and 2.381(9)Å] and also linked to three different L¹ ligands through their terminal (CS) sulphur atoms. Each ligand is in turn bridging two antimony centres. The potential sulphur donors on the ligand rings do not participate in co-ordination; Sb–S distances of 3.085(15), 3.112(4), and 3.407(16)Å reflect a weak type of interaction and this is confirmed by the lack of change in the ¹H and ¹³C n.m.r. spectra of the ligand on complexation. Mössbauer spectroscopy shows that the lone pair on the antimony is stereochemically active, operating through the plane formed by the three sulphurs. The structure of the free ligand L¹ is almost planar which is consistent with a delocalised π-electron system.