Mononuclear Antimony(V) Catecholate Complexes with Additional Pyridine Ligands

A series of triarylantimony(V) complexes with p-dimethylaminopyridine and р-cyanopyridine of the general formulas [(Cat)SbAr3(р-Me2N–Py)] (complexes I–IV) and [(Cat)SbAr3(р-CN–Py)] (complexes V–VII) has been synthesized. Their molecular structures and electrochemical properties have been studied. 3,6-Di-tert-butyl-o-benzoquinone, 4,5-piperazine-1,4-diyl-3,6-di-tert-butyl-o-benzoquinone, and 4,5-dichloro-3,6-di-tert-butyl-o-benzoquinone are used as redox-active ligands. The molecular structures of several complexes in the crystalline state are determined by X-ray diffraction analysis (CIF files CCDC nos. 1974173 (I ⋅ 0.5toluene), 1974174 (II ⋅ 2toluene), 1974175 (V), 1974176 (VI ⋅ hexane), and 1974177 (VII)). All complexes have a distorted octahedral structure, and an additional neutral pyridine ligand occupies one of the apical positions. Electrochemical transformations of the complexes are studied by cyclic voltammetry in a dichloromethane solution. The introduction of substituted pyridine into the molecule of the complex does not change the electrooxidation mechanism of the complexes. For all complexes with р-dimethylaminopyridine, both oxidation potentials are shifted to the cathodic region (0.13–0.21 V for the potential of the first oxidation process and to 0.3–0.4 V for the potential of the second oxidation process). A similar shift for the complex with p-cyanopyridine is less pronounced (0.05 V for the potential of the first oxidation process of complex V as compared to that of complex I).