The antimony halide-aided stereospecific coordination of a cyclic thiourea-type of ligand is observed for the first time. The antimony(III) imidazole thione complexes syn-[(L1)SbCl3] (syn-1) and anti-[(L1)SbBr3] (anti-2) have been synthesized in very good yield by the reaction between the spatially defined steric impact ligand [(IPaul)S] (L1) ([(IPaul)S]=1,3-bis(2,4-methyl-6-diphenyl phenyl)imidazole thione) and corresponding antimony halide. The stereoselective formation of complexes syn-1 and anti-2 has been confirmed by both NMR and single-crystal X-ray diffraction studies. Interestingly the stereospecific nature of syn-1 and anti-2 remains intact in solution. Furthermore, the thermal stability of antimony(III) imidazole thione complexes were examined by TGA analysis. © 2021 Wiley-VCH GmbH