Abstract
Two oxidovanadium(V) complexes, [VOL1L] (1) and [VOL2L] (2) (L = ethyl maltolate), derived from the aroylhydrazones 4-bromo-N'-(2-hydroxy-5-methylbenzylidene)benzohydrazide (H2L1) and N'-(3,5-dibromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2L2), respectively, have been synthesized and characterized by elemental analysis, infrared and electronic spectroscopy. Structures of the complexes were further confirmed by single crystal X-ray determination. The V atoms in the complexes are coordinated by the ONO donor atoms of the aroylhydrazone ligand, OO donor atoms of the ethyl maltolate ligand, and one oxido O atom, forming octahedral coordination. The complexes function as effective olefin epoxidation catalysts with hydrogen peroxide as terminal oxidant and sodium hydrogen carbonate as a co-catalyst.
Highlights
Schiff base complexes have gained remarkable attention due to their interesting applications in the development of new materials like catalysts, and biological applications like DNA cleavage, antibacterial, antiviral and antifungal agents.[1]
As a continuation of such work, we report in this paper two new vanadium(V) complexes [VOL1L] (1) and [VOL2L] (2) (L = ethyl maltolate), derived from the aroylhydrazones 4-bromo-N’-(2-hydroxy-5-methylbenzylidene)benzohydrazide (H2L1) and N’-(3,5-dibromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2L2)
The two complexes were readily prepared from the reaction of the corresponding aroylhydrazone ligands and VO(acac)[2]
Summary
Schiff base complexes have gained remarkable attention due to their interesting applications in the development of new materials like catalysts, and biological applications like DNA cleavage, antibacterial, antiviral and antifungal agents.[1] Metal complexes of hydrazone type Schiff bases were used as catalysts for the organic synthesis, such as olefin polymerization and epoxidation reactions.[2] Among the various metal ions, the complexes of vanadium have received considerable interest in their biochemical significance and industrial catalytic processes.[3] For instance, the use of vanadium complexes in asymmetric synthesis, in C–C bond formation as well as in C–C, C–O and C–H bond cleavages, catalytic oxidation of various olefins, oxidative halogenation and selective epoxidation of unsaturated hydrocarbons and allyl alcohols.[4] Aroylhydrazones bearing typical –CO–NH–N=CH– group are interesting ligands in the preparation of various metal complexes which have considerable biological and catalytic properties.[5] To date, a number of vanadium complexes have been obtained. Our research group has reported some vanadium complexes and their catalytic epoxidation property.[6] As a continuation of such work, we report in this paper two new vanadium(V) complexes [VOL1L] (1) and [VOL2L] (2) (L = ethyl maltolate), derived from the aroylhydrazones 4-bromo-N’-(2-hydroxy-5-methylbenzylidene)benzohydrazide (H2L1) and N’-(3,5-dibromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H2L2)
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