Dioxomolybdenum (VI) and dioxouranium (VI) complexes of tetradentate amidate ligands

Abstract

Dioxomolybdenum(VI) and dioxouranium(VI) complexes of dibasic tetradentate ligands having amide groups have been synthesized. The ligands (LH2) obtained by the condensation of methylsalicylate and 1,2-diaminoethane (H 2ensal), 1,2-diaminopropane (H2-1,2-pnsal) or 1,3-diaminopropane (H2-1,3-pnsal) react with [MoO 2(acac)2] or UO2(CH3COO) 2 in 1:1 molar ratio in refluxing methanol to give complexes of the formula [MoO2L] and [UO2L. MeOH], respectively. IR, electronic and 1H NMR spectroscopy have been used to characterize these complexes. The nitrogen of the -NHCO- group is coordinated in its neutral form in these complexes. Thermogravimetric studies confirm the coordination of methanol in uranium complexes and a weak association in one of the molybdenum complex, [MoO2(1,3-pnsal)].MeOH. On the basis of spectroscopic studies dibasic tetradentate behaviour of these ligands, octahedral structure for dioxomolybdenum(VI) and pentagonal bipyramidal structure for dioxouranium(VI) complexes has been proposed.