Dioxidomolybdenum(VI) complexes of tridentate ONO donor aroylhydrazones: Syntheses, spectral and structural characterization

Abstract

Four dioxidomolybdenum(VI) complexes, [MoO2(L1)(H2O)] (1), [MoO2(L1)(H2O)]·(4,4′-bipy) (2), [(MoO2(L1))2(4,4′-bipy)]·2H2O (3) and [MoO2(L2)(DMF)] (4), of two tridentate ONO donor aroylhydrazones, H2L1 and H2L2 (where H2L1=3-methoxy-2-hydroxybenzaldehyde-2-furoic acid hydrazone and H2L2=4-benzyloxy-2-hydroxybenzaldehyde-4-nitrobenzoic hydrazone), have been synthesized and characterized by partial elemental analyses, molar conductivity measurements, FT-IR and electronic spectral studies. A distorted octahedral geometry was established for all the complexes using single crystal XRD studies. In all the complexes, the aroylhydrazone coordinates to the MoO22+ core through the phenolate oxygen, azomethine nitrogen and iminolate oxygen atoms, furnishing a vacant coordination site that can be utilized for binding of substrates like solvents or heterocyclic bases. The monomeric complexes [MoO2(L1)(H2O)] (1) and [MoO2(L2)(DMF)] (4) were formed by the stoichiometric reaction of MoO2(acac)2 with the respective aroylhydrazones. The reaction of H2L1 with MoO2(acac)2 and 4,4′-bipyridine in an equimolar ratio yielded the 4,4′-bipyridine adduct [MoO2(L1)(H2O)]·(4,4′-bipy) (2), whereas the binuclear complex [(MoO2(L1))2(4,4′-bipy)]·2H2O (3) was formed, in which 4,4′-bipyridine acts as a bidentate linker between two molybdenum centers, by taking twice the molar concentration of 4,4′-bipyridine.