The thermal behaviour of complexes of the type M(HIm)2ac2 (HIm=imidazole,ac=acetate,M=Co, Ni, Cu) is different. Comparable to the thermal degradation of Ni(acac)2(HIm)2  the Ni(HIm)2ac2 loss acetic acid by formation of Ni(Im)2. All nitrogen ligands are splitt off from the copper complex by formation of stable basic copper acetate. The cobalt compound
eliminated acetic acid partially while acetate and imidazolate bridging species are obtained.
The thermal behaviour of the acetate complexes of pyrazole and the bulky 3,5-dimethylpyrazole is quite similar. In a first
step pyrazoliumacetate is removed.
The crystal structure of Ni(HPz)4ac2 is determined by X-ray diffraction: monocline, space group C 2/c.
The water molecule represents the centre of two N−H...O−H...O-bridges. The system of H-bridges in the compound relieves the
proton transfer, indicated by the elimination of pyrazolium acetate.