Sodium bicarbonate assisted oxidation, by H2O2, of styrene and cyclohexene using polymer grafted dioxidomolybdenum(VI) complex as a catalyst

A hydrogen-bonded assembly of cucurbit[6]uril and [MoO2Cl2(H2O)2] with catalytic efficacy for the one-pot conversion of olefins to alkoxy products

The reaction of the macrocyclic cavitand cucurbit[6]uril (CB[6]) and the diaqua complex [MoO₂Cl₂(H₂O)₂] in hydrochloric acid solution gave a water insoluble supramolecular compound with the general composition 2[MoO₂Cl₂(H₂O)₂]·CB[6]·xH₂O·yHCl·z(CH₃COCH₃) (2). Single crystal X-ray diffraction (XRD) analysis revealed the presence of barrel-shape supramolecular entities, {CB[6]·10(H₂O)}, aligned in layers which are shifted relative to adjacent layers to form a brick-like pattern. The CB[6]/water hydrogen-bonded entities further engage in intermolecular interactions with water, HCl and [MoO₂Cl₂(H₂O)₂] molecules to form a three-dimensional (3D) framework. Compound 2 was characterised by thermogravimetric analysis (TGA), IR and Raman vibrational spectroscopy, and ¹³C{¹H} CP MAS NMR. The reference complex [MoO₂Cl₂(H₂O)₂]·(diglyme)₂ (1) and compound 2 were studied for the oxidative catalytic conversion of olefins (cis-cyclooctene, cyclohexene and styrene) with aqueous H₂O₂ as oxidant. Using alcohols as solvents, 2 was employed in a one-pot two-stage strategy for converting olefins to alkoxy products, which involves oxidation (with H₂O₂) and acid chemistry. Mechanistic studies were carried out using different intermediates as substrates, and the type of solvent and substrate scope were investigated. The results demonstrated the ability of the CB[6]/Mo^VI supramolecular adduct to function as an acid-oxidation multifunctional catalyst, and its recovery and reuse via relatively simple procedures.

Noble metal-free V2O5/g-C3N4 composites for selective oxidation of olefins using hydrogen peroxide as an oxidant

Vanadium pentoxide modified graphitic carbon nitride (V2O5/g-C3N4) composites were prepared through a method of wet impregnation and calcination. The obtained samples were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence, electron spin resonance and N2 adsorption/desorption isotherms. Oxidation of olefins was employed to evaluate the catalytic and photocatalytic activities of the prepared V2O5/g-C3N4 composites. Different weight ratios (1%, 2%, 3%, 4% and 5%) of V2O5 loaded composites were prepared and a 3% loaded composite was found to show optimal catalytic performance for the reaction. This noble metal-free catalyst showed excellent performance in the oxidation of styrene to benzaldehyde with high conversion (98.7%) and selectivity (88.4%) under visible light irradiation. A plausible mechanism was proposed for this oxidation reaction with hydrogen peroxide as an oxidant. Other styrene substrates were also selectively transformed to their corresponding aldehydes with high yields (up to 92%), using such a noble metal-free catalytic system.

Effect of N-based additive on the optimization of liquid phase oxidation of bicyclic, cyclic and aromatic alcohols catalyzed by dioxidomolybdenum(vi) and oxidoperoxidomolybdenum(vi) complexes

Catalytic potentials of [Mo^VIO₂]²⁺ and [Mo^VIO(O₂)]²⁺ complexes with dibasic tridentate ONO donor ligands for the oxidation of bicyclic, cyclic and aromatic alcohols in the presence of NEt₃ are reported.