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

Abstract

Mononuclear molybdenum(VI) [MoO 2L 2] ( 1a, 1b, 2a, 2b) and dinuclear molybdenum(V) [Mo 2O 4(L 1b ) 2(CH 3OH) 2] ( 3b) complexes have been prepared by the reaction of [MoO 2(acac) 2] or [Mo 2O 3(acac) 4] (acac=acetylacetonate ion), respectively, with the appropriate β ′-hydroxy-β-enaminones ( HL). Also, two isomeric enaminones ( HL 1a and HL 1b ) 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-MoO 2 2+ cores, while the dinuclear molybdenum(V) complex contains a Mo 2O 4 2+ 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 CH 3OH 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 HL 1b have been determined by a single crystal X-ray diffraction method.