Complexes with free donor atoms, as potential metalloligands, are important building blocks in crystal engineering of coordination polymers and metal organic frameworks. In this work, the possibility of formation of cobalt(II) complexes with free N-donor atoms based on acetone isonicotinoyl hydrazone (Hisn), is verified. Syntheses, X-ray crystal structures and spectroscopic properties of two new cobalt(II) compounds with this hydrazone, are reported. The structural studies reveal the formation of a cationic complex in [Co(Hisn)2(H2O)2](NO3)2 (1) containing keto ligands (Hisn) as well as a neutral complex [Co(isn)2(py)2]n (2), with the deprotonated hydrazone (isn) in its enolate form. Both complexes, with two various tautomers of the hydrazone, contain uncoordinated pyridyl groups that allows to regard them as potential N-donor metalloligands.
