Synthesis, characterization and catalytic activity of addition compounds of dioxomolybdenum(VI) pyridine-2,6-dicarboxylate.: Crystal structure of MoO2(dipic)(L) (L = DMF, DMSO, OPPh3)

MoO2(dipic)(L) (dipic=pyrictine 2.6-dicarboxyiate (dipicolinate): L=dimethyl folmamide (DMF), dimethyl sulfoxide (DMSO), hexamethyl phosphorotriamide (HMPA), triphenylphosphine oxide (OPPh3), triethylamine, tripropylamine, tributylamine, pyridine. 2-methylpyridine, 3-methylpyridine. 4-methylpyridine) have been prepared by reacting equimolar amounts of MoO2Cl2(L)(2) (L = DMF, DMSO) with Na(2)dipic, followed by addition of the appropriate ligand to the resulting solutions. The molecular structures of the DMF, DMSO and HMPA derivatives have been established by X-ray diffraction analysis. The ability of MoO2(dipic)(L) (L = DMF, DMSO, HMPA, OPPh3) to work as oxotransfer catalysts has been examined and compared with that of the prototypical MoO2(Et(2)dtc)(2) (Et(2)dte = diethyl dithiocarbamate). Dipicolinate complexes proved to be more efficient catalysts than dithiocarbamate for the deoxygenation of azoxybenzene with triphenylphosphine: in boiling toluene. (C) 2000 Elsevier Science B.V. All rights reserved.