Abstract
A pair of structurally similar new dioxomolybdenum(VI) complexes, [MoO2L1(EtOH)]·EtOH (1) and [MoO2L2(MeOH)] (2), where L1 and L2 are the dianionic form of 2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol (H2L1) and 2-ethoxy-6-[(2-hydroxyphenylimino)methyl]phenol (H2L2), respectively, were prepared and characterized by IR and UV-Vis spectroscopy, as well as single crystal X-ray diffraction. X-ray analyses indicate that the complexes are dioxomolybdenum(VI) species. Complex 1 contains ethanol as co-ligand, and complex 2 contains methanol as co-ligand. The coordination geometry around the Mo atoms can be described as distorted octahedron, with one imino-N and two phenolate-O of the Schiff base ligand, and one oxo group defining the equatorial plane, and with the other oxo group and one solvent-O occupying the axial positions. The catalytic oxidation property of the complexes with tert-butylhydroperoxide in CH2Cl2 was studied. Both complexes have excellent catalytic properties on cyclooctene and cyclohexene, and good properties on 1-hexene and 1-octene.
Highlights
Schiff base complexes have various catalytic properties, such as ring opening polymerization of cycloalkenes,[1] oxidation of hydrocarbons,[2] ring opening of large cycloalkanes,[3] reduction of ketones to alcohols,[4] alkylation of allylic substrates,[5] improve enantioselectivity in the cyclopropanation reactions.[6]
The Schiff base ligands H2L1 and H2L2 were readily prepared by the condensation reaction of 2-aminophenol with 3-methoxysalicylaldehyde and 3-ethoxysalicylaldehyde, respectively
The coordination geometry around the Mo atom can be described as distorted octahedron, with one imino-N and two phenolate-O of the Schiff base ligand, and one oxo group defining the equatorial plane, and with the other oxo group and one ethanol-O occupying the axial positions
Summary
Schiff base complexes have various catalytic properties, such as ring opening polymerization of cycloalkenes,[1] oxidation of hydrocarbons,[2] ring opening of large cycloalkanes,[3] reduction of ketones to alcohols,[4] alkylation of allylic substrates,[5] improve enantioselectivity in the cyclopropanation reactions.[6] The capability of molybdenum to formation of complexes with oxygen-, nitrogen-, and sulfur-containing ligands led to development of molybdenum Schiff base complexes which are efficient catalysts both in homogeneous and heterogeneous reactions.[7] The properties of the complexes vary obviously with the different types of ligands and coordination sites. H2L1: X = OMe; H2L2: X = OEt have reported a molybdenum complex with hydrazone ligand and its catalytic property.[8] In the present work, two new dioxomolybdenum(VI) complexes with Schiff base ligands 2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol (H2L1) and 2-ethoxy-6-[(2-hydroxyphenylimino) methyl]phenol (H2L2; Scheme 1), [MoO2L1(EtOH)]·EtOH (1) and [MoO2L2(MeOH)] (2), are presented
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