Synthesis and characterization of homobimetallic molybdenum(VI) complexes of a dihydrazone as efficient catalysts for the synthesis of hexahydroxyquinolines via multicomponent Hantzsch reaction

Abstract

Four homobimetallic molybdenum(VI) complexes [(MoO2)2L(D)2] (1–4) (where D = methanol (1), dimethylsufoxide (2), imidazole (3) and pyridine (4)) derived from a multidentate hydrazone ligand, 1,4-bis(3-ethoxy-2-hydroxybenzaldehyde-carbohydrazonato)butane, H4L were synthesized by the reaction of the same with bis(acetylacetonato)dioxidomolybdenum(VI) in 1:2 ratio in presence of methanol, DMSO, imidazole and pyridine. The dihydrazone and the complexes synthesized are characterized by elemental analysis, various spectroscopic techniques (like FT-IR, UV–Vis and 1H NMR) and TGA analysis. The structure of complex 2 was elucidated by single crystFal X-ray diffraction analysis. The complexes 1–4 are suggested to have six-coordinate octahedral stereochemistry around molybdenum(VI) centres. Moreover, the molybdenum complexes have been successfully utilised as catalysts for the synthesis of hexahydroxyquinolones via multicomponent Hantzsch reaction. Generally, decent conversions have been obtained.