A NOVEL STRUCTURE ARRANGEMENT OF MOLYBDENUM DIMETHYLGLYOXIME COMPLEXES - COMPOUNDS WITH MOON2C2 6-MEMBERED RINGS

Thermal reactions of Mo(CO)(6) with dimethylglyoxime (H(2)DMG) in THF solutions, either in vacuum or under atmospheric pressure, gave three compounds with formulae Mo(H(2)DMG)(3), I, Mo2O6(H(2)DMG)(2), II and M o2O4(CO)(2)(H(2)DMG)(2) III. Spectroscopic studies of these complexes revealed that H(2)DMG is bonded to the molybdenum through the nitrogen atom of one oxime moiety and the oxygen of the other moiety. The hydr ogen atom of the latter oxime was transferred to the nitrogen of the s ame group to form an NH group. LH NMR studies of compounds II and III at various temperatures showed that the hydrogen atom of this NH group was rigid on the NMR time scale while the hydrogen atom of the other oxime was fluxional. A mechanism involving terminal-bridge CO and O ex change was proposed to explain the stereochemical nonrigidity of these complexes. Appearance of a resonance at about 7.1 ppm in the H-1 NMR spectra of II and III due to a deshielded CH proton suggested some sor t of aromaticity in these six membered chelates. Copyright (C) 1996 El sevier Science Ltd.