Polynuclear Cobalt Complexes. I. Preparation and Structure of [(tren)Co(O2, OH) - Co(tren)](ClO4)3 · 3H2O. The title compound is obtained by oxygenation of [Co(tren)(H2O)2]2+ in alcaline solution. An X-ray structure determination shows that the tertiary nitrogen atoms of both chelate groups are cis to the O2 bridge.