Syntheses, characterization, and crystal structures of few dioxomolybdenum(VI) complexes incorporating tridentate hydrazones

Abstract

Three new cis-dioxomolybdenum(VI) complexes, [MoO2(L1)(CH3OH)] (1), [MoO2(L2)(CH3OH)] (2), and [MoO2(L3)(CH3OH)] (3) have been synthesized using three different tridentate hydrazone Schiff bases, (E)-N′-(4-oxopentan-2-ylidene)isonicotinohydrazide (H2L1), (E)-N′-(4-oxo-4-phenylbutan-2-ylidene)isonicotinohydrazide) (H2L2), and (E)-N′-(2,3-dihydroxybenzylidene)benzohydrazide (H2L3), respectively. The ligands and their metal complexes were characterized by different physicochemical techniques. The molecular structures of the complexes were conclusively established by single crystal X-ray diffraction which reveals that six coordinated molybdenum(VI) atom adopts distorted octahedral geometry. The tridentate hydrazone coordinates to the metal centers in their di-anionic form. The crystal packing of the complexes also reveals that classical hydrogen bonding between adjacent units result in stair-like 1D structure for 1 while an interlocked dimer for 2 and 3, respectively. Crystal packing also reveals that further non-classical interactions lead to 2D (for 1 and 3) and 3D (for 2) supramolecular structures in their solid state. Hirshfeld surface analyses were carried out to get insight to the intermolecular interactions. Thermal stabilities and electrochemical behavior of the complexes have also been investigated.