Synthesis and structures of two molybdenum(VI) complexes derived from similar benzohydrazone ligands with catalytic properties

Abstract

Two new structurally similar molybdenum(VI) complexes, [MoO2L1(CH3OH)] (1) and [MoO2L2(CH3OH)] (2), where L1 is the dianionic form of N′-(2-hydroxy-5-nitrobenzylidene)-2-methylbenzohydrazide and L2 is the dianionic form of N′-(2-hydroxy-4-methoxybenzylidene)-2-methylbenzohydrazide, were prepared and structurally characterized by elemental analysis, infrared spectra, and single-crystal X-ray diffraction. 1 crystallizes in the monoclinic space group P21/c, with unit cell dimensions a = 7.941(1), b = 14.337(2), c = 15.141(2) Å, β = 92.782(2)°, V = 1721.8(4) Å3, Z = 4, R1 = 0.0286, wR2 = 0.0650, GOOF = 1.028. 2 crystallizes in the triclinic space group P-1, with unit cell dimensions a = 8.003(1), b = 10.608(1), c = 10.880(1) Å, α = 95.745(2)°, β = 97.627(2)°, γ = 105.762(2)°, V = 872.0(2) Å3, Z = 2, R1 = 0.0226, wR2 = 0.0595, GOOF = 1.116. X-ray analysis indicates that Mo in the complexes are coordinated by the phenolate oxygen, imino nitrogen, and enolate oxygen of the benzohydrazone, methanol, and two oxo groups, generating octahedral coordination. The oxidation of olefins with the complexes as catalysts was evaluated, indicating that the complexes showed excellent catalytic efficiency in oxidation of most aliphatic and aromatic substrates under mild conditions using tert-butyl hydrogen peroxide as oxidant.