Two series of oxo-bridged Co(III) complexes of the type Co4O4(O2CC6H4-X)(4)(py)(4) (1) and Co4O4(O2CC6H4-X)(4)(4-Mepy)(4) (2), where X = H (a), Me (b), MeO (c), Cl (d), NO2 (e), have been synthesized and characterized in detail. The molecular structures of the complexes consist of a cubelike Co-4(mu(3)-O)(4) core having Co and O atoms at alternate vertices with carboxylato ligands bridging the Co3+ ions along four face diagonals of the approximate cube. Nitrogen atoms from pyridyl ligands complete the distorted-octahedral coordination around each Co(III). These neutral Co(III) complexes undergo a nearly reversible one-electron oxidation involving the redox couple [Co-4(III)(mu(3)-O)(4)](4+) <-> [(Co3CoIV)-Co-III(mu(3)-O)(4)](5+) at potentials (similar to 0.7-1.0 V) that linearly depend on the electronic influence of X, The cobalt(III) clusters of types 1 and 2 have been found to effectively promote the TBHP oxidation of benzylic alcohols under homogeneous conditions to produce the corresponding carbonyl compounds,