Catalytic efficacy of an oxido-peroxido tungsten(VI) complex: synthesis, X-ray structure and oxidation of sulfides and olefins

Abstract

An oxido-peroxido tungsten(VI) complex [WO(O 2 )L(CH 3 OH)] using salicylidene benzoyl hydrazine as a tridentate ONO donor Schiff base (H 2 L) has been synthesized and characterized by elemental analysis, IR, 1 H NMR, molar conductance data, and single-crystal X-ray analysis. The complex was used as a catalyst for epoxidation of olefins and oxidation of sulfides. The results show that epoxides and sulfoxides were produced in high yield, turnover number, and selectivity. IntroductionOxido and peroxido transition metal compounds have played an important role in oxidation of organic substrates. A variety of peroxido complexes of various metals are known to catalyze the oxidation of olefins, arenes, phenols, alcohols, phosphines, and sulfides [1-3]. The catalytic activity of peroxido metal complexes is influenced by the type of metal, the number of peroxido ligands attached to the catalyst and the nature of the remaining ligands in the coordination sphere [3][4][5][6].Current interest in tungsten is due to the importance of the metal as an essential trace element that participates in a number of important enzymatic reactions [7]. There are a few reports on preparation and catalytic activity of oxido-peroxide tungsten(VI) complexes in oxidation reactions [8][9][10].We recently reported a highly efficient method for oxidation of olefins and sulfides by using an oxido-peroxido Mo(VI) complex [MoO(O 2 )L(CH 3 OH)] with salicylidene benzoyl hydrazine (H 2 L) as ligand [11]. In order to study the effect of metal on catalytic reactivity, herein we report the synthesis, characterization, and comparative catalytic activity of a new oxido-peroxido W(VI) complex [WO(O 2 )L(CH 3 OH)] in oxidation of olefins and sulfides under the same condition as given in our previous work (scheme 1).

Nanoparticle supported, magnetically separable manganese porphyrin as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions

“…Comparison of the catalytic performances presented in this work with those of other similar studies [61][62][63][64][65][66][67] reveals that our catalytic system is superior to some of the previously reported catalysts in terms of catalytic activity (TON) and reaction conditions. The high turnover number of our catalyst compared to recently reported protocols 61,62 makes the Fe 3 O 4 @SiO 2 -NH 2 @[MnTPFPP] more attractive for oxidation of hydrocarbons.…”

“…According to the molar ratio of 1/250/500 for catalyst/substrate/oxidant which is carried out in this work, the amount of catalyst which is used in each run (0.01 g, containing 8 Â 10 À4 mmol of MnPor) is lower than that of previous works. [61][62][63][64][65][66] It is observed that in several articles, 62,65 performance of the catalyst in oxidation of various substrates was inspected under reux, while the oxidation reactions were carried out at room temperature in this work. It should be mentioned that the insertion of an oxygen atom within the C-H of a saturated carbon atom is one of the most difficult reactions to achieve with a catalyst at room temperature.…”

“…Our heterogenized catalytic system, can be recovered and reused in comparison with the homogeneous complexes. [61][62][63][64] Metal complexes are stabilized upon immobilization on solid supports because of the support environment. Also, the formation of inactive dimer, the major drawback of homogeneous catalyst, is prevented by site isolation on the surface.…”

Oxido‐peroxido W(VI)‐histidine–MgAl‐layered double hydroxide composite as an efficient catalyst in sulfide oxidation

“…All chemicals and solvents were obtained from Merck and Fluka Inc. and were used without further purification. Layered double hydroxide (LDH) with Mg 1‐ x Al x (OH) 2 (Cl) x .zH 2 O composition and WO 3 were synthesized described in previous reported procedures …”