Azido(imidazole)bis(acetylacetonato)cobalt(III) Complexes — Facile tränst eis Interconversion in Solution

Azido Coordination, Imidazole Adducts, Structural Interconversion A number of mixed-ligand complexes of cobalt(III) containing coordinated azide ion, acetylacetonate anion and the neutral base imidazole and, having the general formula [Co(acac)2(N3)(Im)] (Im = imidazole or its derivatives) have been synthesised by the reaction of K[rrans-Co(acac)2(N3)2] with the biologically active ligand imidazole or its derivatives. IR and electronic spectra alongwith 'H and C NMR spectra have been employed to characterise the complexes and determine their geometry. In contrast to the stable f/w7s-[Co(acac)2(N02)(Im)] complexes, these azido complexes are shown to undergo facile trans^eis interconversion in CHC13 solution. The NMR spectra ( 'H and C) can be interpreted by assuming the presence of an equilibrium mixture of the eisand /rarts-isomers in solution.