Immobilization of monomeric organometallic molybdenum oxo and carbonyl complexes and their application in epoxidation reactions

Abstract

Various oxomolybdenum complexes are efficient and selective homogeneous catalysts in the presence of organic hydroperoxides. The increasing interest in the heterogenisation of such catalysts has led to an increased interest in finding suitable support materials for the complexes. These supports include ionic liquids, mesoporous materials and zeolites to name a few. Several methods are used to anchor the catalyst depending on the nature of the carrier material. The supported catalysts combine properties of homogeneous catalysts such as reactivity, control and selectivity with those of heterogeneous catalysts such as enhanced stability and recyclability.

Dioxomolybdenum(VI) Epoxidation Catalyst Supported on Mesoporous Silica Containing Phosphane Oxide Groups

“…The epoxide yields at 24 h are comparable with those reported in the literature for several micelle-templated mesoporous silica-supported complexes of the type [MoO 2 Cl 2 L] or [CpMo(CO) 3 (X)] (Cp = cyclopentadienyl ligand; X = methyl, siloxane) possessing a -Si(OEt) 3 moiety on the L, Cp or X ligand. [7] The kinetic curve for LP-TEPPPO-Mo is comparable to that of MCM-41-supported [MoO(O) 2 L] complexes, used as a catalyst in the same reaction. [8,9] The LP-TEPPPO-Mo catalyst was further tested in the reactions of (R)-(+)-limonene, 1-octene and trans-2-octene with tBuOOH, at 55°C, without a co-solvent (Table 1).…”

Grafting of Molecularly Ordered Mesoporous Phenylene‐Silica with Molybdenum Carbonyl Complexes: Efficient Heterogeneous Catalysts for the Epoxidation of Olefins

“…[25] In particular, cyclopentadienylmolybdenum tricarbonyl complexes of the type Cp'Mo(CO) 3 X (X = Cl, alkyl) have been immobilized in ordered mesoporous silicas by either direct grafting or tethering via ligands, and examined as precursors to heterogeneous catalysts for the epoxidation of olefins with TBHP as the oxidant. [26] The tricarbonyl complexes undergo oxidative decarbonylation in situ with TBHP to give supported oxomolybdenum(VI) species such as Cp'MoO 2 X and/or Cp'MoO(O 2 )X.…”

“…) followed the order DCE (1075) > acetonitrile (820)ffitoluene (789) > n-decane (217) > ethanol (26). No clear relationship exists between the dielectric properties of these solvents and the catalytic activity, which may be at least partly because of the major differences in polarity between the olefin and the oxidant.…”

Effect of an Ionic Liquid on the Catalytic Performance of Thiocyanatodioxomolybdenum(VI) Complexes for the Oxidation of Cyclooctene and Benzyl Alcohol

“…This method provides a nonaqueous alternative for two-phase catalysis, in which the catalyst is ''immobilised'' and easily separated from the products [26][27][28]. Promising results have been reported for cyclooctene epoxidation using various room temperature ionic liquids (RTIL) as reaction solvents, TBHP [29,30] or urea-hydrogen peroxide adduct [31] as oxidants, and molybdenum(VI) complexes as catalysts.…”