The synthesis, characterization and crystal structure of a tetranuclear cobalt(III) coordination compound, [Co4(L)4](HSO4)2(SO4)·4.1(CH3OH)·H2O (1), with thiocarbohydrazone based ligand is reported. This compound can efficiently catalyze the reduction of oxygen (O2) by a weak electron donor ferrocene, (Fc), at the polarized water/dichloroethane interface which was investigated by voltammetry and biphasic shake‐flask experiments. Compound 1 contains four cobalt cores which are connected together by sulphur atoms. By having four cobalt cores this coordination compound provides a multi‐electron transfer system for oxygen reduction reactions. The results also suggest that compound 1 catalyzes decomposition of H2O2 at the interface.

A new dinuclear cobalt(III) coordination compound, [Co 2 L(μ-N 3 )(N 3 ) 2 ]Á CH 3 OH (1), was synthesized and characterized by elemental analysis, spectroscopic methods, and single-crystal X-ray analysis in which H 3 L is a heptadentate ligand obtained by the condensation of triethylenetetramine with 5-bromo-2-hydroxybenzaldehyde. X-ray analysis revealed that two cobalt(III) ions have distorted octahedral geometry and are connected together by a phenoxy and an azide bridging ligand. The catalytic activity of compound 1 for oxygen (O 2 ) reduction reaction was investigated. Compound 1 can efficiently catalyze the reduction of O 2 by a weak electron donor, ferrocene (Fc), at the polarized water-1,2-dichloroethane interface. It was found that compound 1 can catalyze O 2 reduction to H 2 O 2 , whereas in the presence of Fc, it can catalyze the reduction of O 2 to water. K E Y W O R D Sdinuclear cobalt(III) coordination compound, ferrocene, liquid-liquid interface, oxygen reduction reaction