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=dimethy l folmamide (DMF), dimethyl sulfoxide (DMSO), hexamethyl phosphorotriamide (HMPA), triphenylphosphine oxide (OPPh3), triethylamine, tripropylamine, tr ibutylamine, pyridine. 2-methylpyridine, 3-methylpyridine. 4-methylpyridine ) have been prepared by reacting equimolar amounts of MoO2Cl2(L)(2) (L = DM F, DMSO) with Na(2)dipic, followed by addition of the appropriate ligand to the resulting solutions. The molecular structures of the DMF, DMSO and HMP A derivatives have been established by X-ray diffraction analysis. The abil ity of MoO2(dipic)(L) (L = DMF, DMSO, HMPA, OPPh3) to work as oxotransfer c atalysts has been examined and compared with that of the prototypical MoO2( Et(2)dtc)(2) (Et(2)dte = diethyl dithiocarbamate). Dipicolinate complexes p roved to be more efficient catalysts than dithiocarbamate for the deoxygena tion of azoxybenzene with triphenylphosphine: in boiling toluene. (C) 2000 Elsevier Science B.V. All rights reserved.