Synthesis, characterization, molecular and supramolecular structures of nickel(II) complexes derived from α-diketone and α-ketoaldehyde bisaroylhydrazones

A new series of nickel(II) complexes derived from symmetrical diacetyl bisaroylhydrazones [Ni(L1-R)] and unsymmetric phenylglyoxal bisaroylhydrazones [Ni(L2-R)] have been prepared and characterized. X-ray crystal and molecular structures of [Ni(L1-H)], [Ni(L1-pCH3O)] and [Ni(L1-pNO2)] have been determined. In these complexes, the Ni(II) is in a distorted square planar environment and the aroylhydrazone acts as dinegative tetradentate ligand forming a 5,5,5-tricyclic chelate ring. Reaction of [Ni(L1-R)] with aqueous ammonia afforded the paramagnetic five coordinate [Ni(L1-R)(NH3)] while [Ni(L2-R)] gave the diamagnetic square planar [Ni(L2-R)(NH3)] complexes. Reaction of [Ni(L1-R)] complexes with imidazole gave the corresponding paramagnetic octahedral bis(imidazole) adducts. X-ray structures of both [Ni(L1-H)(HIm)2] and [Ni(L1-pNO2)(HIm)2] suggest a distorted octahedral structure where the bisaroylhydrazone occupies the basal plane while the two imidazoles occupy the axial sites. The molecular units are associated together forming triple stranded helical chains. With imidazole the [Ni(L2-R)] series gave the corresponding diamagnetic mono(imidazole) [Ni(L2-R)(HIm)] complexes, The X-ray structure of {Ni(L2-pCH3)(HIm)] suggest square planar arrangement around the Ni(II) where the bisaroylhydrazone acts as dinegative NNO tridentate ligand forming with the Ni(II) a 5,6-bicyclic chelate ring the fourth coordination site is occupied by imidazole nitrogen.

Ni(II) complexes derived from diacetyl bisaroylhydrazones [Ni(L1-R)] and phenylglyoxal bisaroylhydrazones [Ni(L2-R)] were prepared and characterized. The molecular and supramolecular structures [Ni(L1-H)], [Ni(L1-pCH3O)] and [Ni(L1-pNO2)] were determined by single crystal X-ray analysis. The structure of the mixed ligand Ni(II) complexes [Ni(L1-H)(HIm)2], [Ni(L1-pNO2)(HIm)2] and {Ni(L2-pCH3)(HIm)] were also determined.Figure optionsDownload as PowerPoint slide