NH-ACIDIC BEHAVIOR OF IMIDAZOLE IN THE COURSE OF THE THERMAL-DEGRADATION OF ITS BIS(ADDUCTS) WITH TRANSITION-METAL 1,3-DIKETONATES

The behaviour of complexes of the type M(O-O)2(HIm)2 (O-O = 1,3-diketonate, HIm = imidazole, M = Co, Ni, Cu) in the course of the thermal degradation is different. In the case of M(acac)2(HIm)2 in the first step acetylacetone is split off. By proton transfer from imidazole to the acetylacetonato ligands the bis(imidazolates) M(Im)2 are formed, which, at higher temperatures eliminate both imidazolyl residues, probably as 1H, 1H'-(2,2')-bisimidazolyl. The thermal degradation of M(bzac)2(HIm)2 or M(dbm)2(HIm)2 (Hbzac = benzoylacetone, Hdbm dibenzoylmethane) starts with the partial elimination of imidazole. The intermediates M(bzac)(Im) or M(dbm)(Im) are obtained, and the final product of thermal degradation is the metal oxide. The main reasons for the different thermal behaviour of the complexes M(O-O)2(HIm)2 are differences in the volatility of the 1,3-diketones and probably in the molecular structures.