Intracomplex Dioxomolybdenum(VI) Compounds with Alcoholimines of Aromatic o-Hydroxyaldehydes. Crystal Structure of 2-Hydroxynaphthylidene Monoethanolimine (H2L) and Solvated Complex [MoO2(L) · C5H5N]

A Schiff base, which is a derivative of 2-hydroxynaphthaldehyde and monoethanolamine (H2L), and an intracomplex compound of dioxomolybdenum(VI) [MoO2(L) · C5H5N] (I) have been synthesized. The structures of H2L and I have been determined by IR spectroscopy and X-ray diffraction. In the mononuclear molecule I, the Mo atom has an octahedral coordination formed by two oxo-ligands (Mo=O 1.683(4) and 1.697(3) Å), two O atoms of deprotonated hydroxy groups of the alcohol (Mo–O(4) 1.919(4) Å) and aldehyde (Mo–O(3) 1.962(3) Å) fragments, as well as the N atom of the tridentate bis-chelate doubly charged ligand L2– (Mo–NL 2.262(4) Å) and the N atom of the pyridine molecule (Mo–NPy 2.496(4) Å). The Mo–NL and Mo–NPy bonds are significantly elongated due to the structural manifestation of trans-influence of multiply bound oxo ligands. The free H2L molecule crystallizes in the quinoid (keto-amine) tautomeric form, and in complex I it is coordinated in the double-deprotonated benzoid (enol-imine) form.