3-(arylhydrazono)pentane-2,4-diones and their complexes with copper(II) and nickel(II) - Synthesis and crystal structures

A series of new 3-(arylhydrazono)pentane-2,4-diones (1-6) synthesized from pentane-2,4-dione and diazonium salts of respective anilines using the procedure of Japp-Klingemann are described. Complexes with Cu-II and Ni-II salts are prepared (7-10, respectively). Spectroscopic properties of these compounds have been studied and X-ray crystal structures of selected hydrazones (3, 4, 6) and of the hydrazone complexes (7-10) are reported. The structures of the uncomplexed hydrazones feature an intramolecular N-H center dot center dot center dot O interaction to yield a six-membered H-bond ring reflecting preference of the hydrazone tautomeric structure. All the complexes are mononuclear 2:1 (L:M) structures of six-membered chelate type involving N2O2 binding sites that are quadratic arranged but differ in the entire coordination environment dependent on the metal and the ligand substitution including distorted octahedral and quadratic pyramidal coordination geometries in the Cu-II complexes 7 and 8 or nearly regular square planar coordination geometry in the Ni-II complexes 9 and 10, respectively. In the crystal packings, strong and weak H-bond interactions cause supramolecular network structures.