Reactions of oxygenated cobalt (II) complexes. XIII . Diastereoisomeric forms of μ‐peroxo‐μ‐hydroxo‐bis[bis(ethylenediamine) cobalt(III)]. Preparation, X‐ray structure determination and reactivity

Oxygenation of solutions containing bis(ethylenediamine) cobalt(II) ions leads to a mixture of diastereomeric forms of μ‐peroxo‐μ‐hydroxo‐bis[bis(ethylenediamine) cobalt(III)] cations. The existence of a meso‐isomer has now been proved by its isolation as perchlorate and by an X‐ray structure determination. The crystals are monoclinic with space group P2 1 /n and lattice constants: a = 19.280, b = 11.984, c = 11.654 Å, β = 99.190°. The UV./VIS. spectra of the isomers are practically identical but show different kinetic behaviour. In acidic solution the meso‐isomer decomposes 4 times faster than the racemic form. In alkaline solution the meso‐isomer isomerizes to the racemic form. A mechanism which explains all the kinetic observations has been devised.