Chiral metal complexes. 17. Cocrystallization of four diastereoisomers: a second example

Recently the crystal structure of [Co(acac) (R-dqpn')] C1O₄ was described⁴ as comprising equal amounts of Δ-β and Δ-β cations with positional disorder of the pn methyl group. Another isomerism was present in that the nitrogen α or β to the asymmetric carbon could be deprotonated. Nevertheless, only two doublets due to these methyl groups were observed in the ¹H NMR spectrum of the complex and its conjugate acid, and this was interpreted as arising from a facile rearrangement of the diastereomer population in solution.