Synthesis, characterization and crystal structures of molybdenum(VI) and (V) complexes with differently N-substituted beta '-hydroxy-beta-enaminones

摘要

Mononuclear molybdenum(VI) [MoO2L2] (1a, 1b, 2a, 2b) and dinuclear molybdenum(V) [Mo2O4(L-1b)(2)(CH3OH)(2)] (3b) complexes have been prepared by the reaction of [MoO2(acac)(2)] or [Mo2O3(acac)(4)] (acac = acetylacetonate ion), respectively, with the appropriate beta'-hydroxy-beta-enaminones (HL). Also, two isomeric enaminones (HL1a and HL1b) have been prepared by the reaction of ethyl 2-hydroxy-4-(4-hydroxy-6-methyl-2H-pyran-2-on-3-yl)-4-oxo-2-butenoate (ehmpb) and o-anisidine. All the prepared molybdenum(VI) complexes are built up of mononuclear molecules with cis-MoO22+ cores, while the dinuclear molybdenum(V) complex contains a Mo2O42+ core. In all complexes ligand L is coordinated in a didentate fashion to molybdenum through two oxygen atoms and not through the nitrogen atom. One neutral solvent molecule CH3OH in the molybdenum(V) complex, acting as a monodentate ligand, completes the octahedral coordination of each Mo atom. All compounds have been characterized by means of chemical analyses, IR and one- and two-dimensional NMR spectroscopy. The molecular and crystal structures of the molybdenum(VI) (1a), molybdenum(V) (3b) complexes and of ligand HL1b have been determined by a single crystal X-ray diffraction method. (C) 2004 Elsevier Ltd. All rights reserved.