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X-ray and NMR Structural Studies of Molybdenum(V) Complexes Coordinated by Enaminones

New dinuclear molybdenum(V) complexes, of general formula [Mo_2O_4L_2D_2], where L is enaminone ligand coordinated through two oxygen atoms (as beta-diketonate), and D is a neutral monodentate ligand (solvent molekule), have been obtained by the reaction of [Mo_2O_3(acac)_4](acac = acetilacetonate ion) with the potential polydentate type of ligands, 4-hydroxy-2-pyrone derivatives. Ligands and complexes have been characterized by means of elemental analyses, ^1H, ^13C and 2d NMR spectroscopy, IR spectra as well as by thermal analyses. The molecular structures of the enaminone ligands have been confirmed by a single crystal X-ray diffraction study. The structure of ligand can be described as consisting of three structural fragments: 2-pyrone ring substituted at position 6 by ethoxycarbonyl group, delocalized central enminone part and N-substituent (phenyl ring with methoxy group on position 4). The complexes contains [Mo_2O_4] core with crystallographically imposed two-fold axis. Each molybdenum atom is coordinated by six oxygen atoms: one terminal oxo-O, two bridging oxo-O, two oxygen atoms from the bidentate ligand molecule and oxygen atom from solvent molecule. NMR data cooborate the existence of an enamine rather than an imine form, which is in agreement with the crystal structure determination.

X-ray; NMR studies; Enaminones; molybdenum(V) complexes

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