Triaryl/trialkylantimony(V) catecholates with electron-acceptor groups

• A series of new antimony(V) catecholates with electron-acceptor substituents.
• Complexes undergo two successive oxidation stages to mono- and dication derivatives.
• A weak dependence of catecholate redox potentials on the nature of groups at antimony.

A number of new antimony(V) complexes of type CatSbR3 (R = ethyl, o-tolyl, p-tolyl, p-fluorophenyl, p-chlorophenyl) with 4-chloro-3,6-di-tert-butyl-catecholato (4-Cl-3,6-DBCat), 6-chloro-, 6-bromo- and 6-nitro-3,5-di-tert-butyl-catecholato (6-X-3,5-DBCat, X = Cl, Br, NO2) redox-active ligands was synthesized and characterized. The molecular structures of (4-Cl-3,6-DBCat)Sb(o-Tol)3 (2), (6-Cl-3,5-DBCat)Sb(p-Tol)3 (7), (6-Br-3,5-DBCat)Sb(p-Tol)3 (8) in crystals were determined by single-crystal X-ray analysis. In the accordance with cyclic voltammetry data, the oxidation of complexes proceeds in two successive stages with a formation of mono- and dicationic derivatives. The modification of Ph groups at antimony with different substituents does not affect appreciably the redox potentials of complexes containing the electron-acceptor groups in redox-active ligand.

Antimony(V) di-tert-butylcatecholates with electron-withdrawing groups in redox-active ligand were synthesized. Complexes (4-Cl-3,6-DBCat)Sb(o-Tol)3, (6-Cl-3,5-DBCat)Sb(p-Tol)3, (6-Br-3,5-DBCat)Sb(p-Tol)3 adopt a distorted trigonal-bipyramidal geometry. The electrochemical oxidation of complexes proceeds on redox-active ligand producing mono- and dicationic derivatives. The nature of substituents at antimony does not influence on the redox potentials of corresponding catecholate.Figure optionsDownload as PowerPoint slide