Coordination chemistry of a bis(benzimidazole) disulfide: eleven membered chelate ring in cobalt(II), zinc(II) and cadmium(II) halide compounds; oxidative disulfide cleavage when coordinated to nickel(II).

Herein we report the synthesis, structural and spectroscopic characterization of coordination compounds with bis[2-(1H-benzimidazol-2-yl)phenyl]disulfide [bis-(2phSbz)] (1) and cobalt(II), zinc(II) and cadmium(II) halides (2-7). Their X-ray diffraction analyses showed that the metal ions present similar distorted tetrahedral structures, with the disulfide ligand coordinated through the imidazolic nitrogen atoms, forming a twisted eleven membered chelate ring. Structures of nickel(II) compounds 8 and 9, showed that the disulfide bond in the ligand was cleaved forming six membered chelates. In 8, the two ligands are sulfides, however in 9 one of them was oxidized to a sulfone. In both compounds the nickel(II) has a distorted square planar geometry and the sulfur atoms are in cis positions. The oxidation reaction of bis-(2phSbz) was performed in KMnO4/NaOH, giving the 2-(1H,3H-benzimidazolium-2-yl)-benzene sulfonate (10). The solid state structure of compounds 2-5 and 7-10 was determined by X-ray diffraction analyses.