Abstract
We report a new mononuclear molybdenum(iv) complex, MoOLBISLSQ, in which LSQ (2,4-di-tert-butyl o-semibenzoquinone ligand) has been prepared from the reaction of the o-iminosemibenzoquinone form of a tridentate non-innocent benzoxazole ligand, LBIS, and MoO2(acac)2. The complex was characterized by X-ray crystallography, elemental analysis, IR and UV-vis spectroscopy and magnetic susceptibility measurements. The crystal structure of MoOLBISLSQ revealed a distorted octahedral geometry around the metal centre, surrounded by one O and two N atoms of LBIS and two O atoms of LSQ. The effective magnetic moment (μeff) of MoOLBISLSQ decreased from 2.36 to 0.2 μB in the temperature range of 290 to 2 K, indicating a singlet ground state caused by antiferromagnetic coupling between the metal and ligand centred unpaired electrons. Also, the latter led to the EPR silence of the complex. Cyclic voltammetry (CV) studies indicate both ligand and metal-centered redox processes. MoOLBISLSQ was applied as a catalyst for the oxidative cleavage of cyclohexene to adipic acid and selective oxidation of sulfides to sulfones with aqueous hydrogen peroxide.
Highlights
Scientists have discovered in recent decades that some enzymes with special ligands are able to perform redox processes at both their metal centers and their coordinated ligands
The synthesis of MoOLBISLSQ complex was performed in 40% yield by re uxing CH2Cl2 solution of a ligand H2LBAP and Et3N with MoO2(acac)[2] (Scheme 2)
Elemental analysis data of the complex are consistent with theoretical ones and con rm the 1 : 1 : 1 : 1 molar ratio of Mo : O : LBIS : LSQ
Summary
Scientists have discovered in recent decades that some enzymes with special ligands are able to perform redox processes at both their metal centers and their coordinated ligands. The redox-active aminophenolate ligand H2LBAP was synthesized from 1 : 2 molar ratio of 2-aminobenzyl amine and 3,5DTBQ.[14] The synthesis of MoOLBISLSQ complex was performed in 40% yield by re uxing CH2Cl2 solution of a ligand H2LBAP and Et3N with MoO2(acac)[2] (Scheme 2). To gain deeper understanding of complex [MoOLBISLSQ], this species, the H2LBAP compound and (LBIS)nÀ and (LSQ)nÀ ligands (n 1⁄4 2, 1, 0), were theoretically analyzed by using the Density Functional Theory (DFT) approach at the B3LYP-LANL2DZ/6311++G** level.
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