Optically Active Cobalt(III) Complexes Containing Partial Cubane Co3O4 Core

Four isomers (T0, T1, T2, and T3) of [Co3(edma)3(μ-OH)3(μ3-O)]Cl (edma: ethylenediamine-N-acetate) containing a partial cubane Co3O4 core were isolated and optically resolved. The geometrical structures and absolute configurations of optically active -T2 chloride-water (1/7) and -T3 chloride-water (1/7) were determined by the X-ray diffraction method. The absolute configurations of optically active T0 and T1 were assigned on the basis of the NMR, UV, and CD spectral data. Each isomer was stable for at least 5 d in its neutral aqueous solution. Reversible protonation accompanying a color change was observed for each isomer in the pH range 2--7; this protonation did not accompany the cleavage of its partial cubane core. However, slow decomposition of each isomer was observed in its 60% HClO4 solution.