Ligand effects on metal-oxygen stretching frequencies in dioxomolybdenum(VI) complexes

Summary Several new seven-coordinated dioxomolybdenum(VI) heterochelates, MoO₂(AA)(BBB)], where AA = bidentate ligand = ethylenediamine, 2-aminoethylpyridine,o-pheny-lenediamine,o-phenanthroline or 2,2-dipyridyl; BBB = tridentate ligand (the Schiff base derived from benzoylhydrazide and salicylaldehyde), have been synthesized and characterized by elemental analysis, molar conductance, molecular weight, i.r. spectra and magnetic susceptibility measurements. The principle of coordination number expansion of a six coordinate homochelate, MoO₂(H₂O)(BBB)] was used to prepare the complexes, which are nonelectrolytes, monomers and diamagnetic. The i.r. spectral data reveal that they possess acis-MoO₂ structure. The _sym(OMoO) and _asym(OMoO) shifts and the difference between _sym(OMoO) and _asym(OMoO) have been related to an increase in electron density at the molybdenum atom therein.