Official URL: https://www.sciencedirect.com/journal/polyhedron

In the absence of a metal ion, racemic trans-1,2-diaminocyclohexane (trans-(�)DCH) reacts with acetylacetone (acacH) (1:2.5 mole ratio) to form the bisoxoenamine condensation product, boe (1). CoCl2·6H2O and Co(ClO4)2·6H2O each react with trans-(�)DCH in air to give complexes containing the oxidised Co(III) ion, [Co((�)DCH)3]3+, which does not subsequently react with added acacH to give a Schiff base complex. Mixtures of complexes are obtained from one-pot reactions involving trans-(�)DCH, a simple Co(II) salt and acacH (1:1:2.5 mole ratio). When CoCl2·6H2O is used, the mixed-ligand Co(II) complex [Co((�)DCH)Cl2] (4) precipitates first and, after a period of weeks, the Co(II) complex (diazH)2[CoCl4] (5) (diazH+ is a diazepinium cation), the Co(II) complex [Co(boe)Cl2]n (6) and the Co(III) complex [Co(acac)3] (7), co-crystallise from the mother liquor. Using Co(ClO4)2·6H2O in the reaction with trans-(�)DCH and acacH also gives a mixture of products. Complexes 7, the Co(II) complex [Co2(acac)4(H2O)2][Co(acac)(H2O)4]ClO4·EtOH (8) and the Co(III) complex [Co(acac)2(�)DCH]ClO4 (9) co-crystallise. Complexes 1, 5, 7, 8 and 9 were characterised using X-ray crystallography. The major difference between using CoCl2·6H2O and Co(ClO4)2·6H2O in reactions involving (�)DCH and acacH is that no DCH/acacH condensation products are identified in the product mixtures when the perchlorate salt is employed.