Preparation And Characterization Of Bidentate Schiff Base Dioxomolybdenum(Ⅵ) Complex Immobilized On CPS Microspheres And Study On Catalytic Property

Immobilized Schiff base dioxomolybdenum (VI) complex, which possessedfavorable selectivity in oxidizing reaction, hydrogenation and aldol condensation, canachieve hydrocarbon’s selective catalytic oxidation, can transform alcohols intoaldehydes or ketone. This paper designs and sets up a new way of crosslinkedpolystyrene microspheres as carrier to manufacture grafted schiff base 2 oxygenmolybdenum catalyst. Firstly, Schiff base adsorbed on the surface of crosslinkedpolystyrene microspheres by chemosetting methods and taken place complexingreaction to manufacture efficiently immobilized Schiff base dioxomolybdenum (VI)complex. The product was provided with efficient catalytic activity and selectivity inreaction process of cyclohexene and phenylcarbinol. On Currently Existing Foundationof prepared immobilized Schiff base dioxomolybdenum (VI) complex, this paperresearched the relation of catalytic activity and major factor. The research of this paper isof importance in organic catalysis area.The nucleophilic substitution reaction between the chloromethyl groups of theswelled CMCPS microspheres and p-hydroxybenzaldehyde (HBA) was first allowed tobe carried out in the presence of acid-acceptor Na2CO3, obtaining aldehydegroup-modified CPS microspheres, BACPS, and then the Schiff base reaction betweenBACPS microspheres and glycine (GL) was conducted, resulting in Schiff base-typechelating resin, BAGL-CPS, in whose structure Schiff base ligand and carboxyl groupare exist at the same time. Its chemical structure was characterized by infrared spectrum.The aldehyde group-modification reaction of CMCPS was mainly investigated, the effects of main factors on the substitution reaction were examined, and the reactionmechanism was speculated and explored. The experimental results show that the rate ofthe nucleophilic substitution reaction is independent of the concentration of thenucleophile HBA, indicating that this is a typical unimolecular nucleophilic substitutionreaction i.e. SN1. The solvent polarity is favourable for the fracture of C-Cl bond of thebenzyl chloride group, and can accelerate the substitution reaction. The increase of thereaction temperature is also advantageous to the substitution reaction. DMF is a suitablesolvent and 90℃is a appropriate temperature.The coordination reaction between BAGL-CPS microspheres and molybdenylacetylacetonate (MoO2(acac)2)) was conducted, obtaining Schiff base dioxomolybdenum (VI) complex-immobilized microspheres CPS-[MoO2(BAGL)2], namely preparingthe heterogeneous dioxomolybdenum (VI) complex catalyst. The micro spheresCPS-[MoO2(BAGL)2] were fully characterized by many means such as FYIR, SEM,TGA and AAS. They were used in the epoxidation of cyclohexene with tert-butylhydroperoxide (TBHP) as oxidant, and their catalytic activity was examined. Theexperimental results show that through the coordination reaction between BAGL-CPSmicrospheres and MoO2(acac)2, the immobilized Schiff base dioxomolybdenum (VI)complex can be successfully prepared.In the epoxidation of cyclohexene, theheterogeneous dioxomolybdenum (VI) complex catalyst CPS- [MoO2(BAGL)2] havevery high catalytic activity and excellent catalytic selectivity, and can effectivelytransform cyclohexene into cyclohexene oxide as a single product. All of the reactiontemperature, solvent polarity and the ratio of substrate to oxidant have great effect on thecatalytic epoxidation reaction of cyclohexene. The weaker the polarity of the solvent, thehigher the activity of the catalyst CPS-[MoO2(BAGL)2] is and the higher the yield ofcyclohexene oxide is. Under the suitable reaction conditions (at the temperature of 80℃,with n-heptane as solvent and in 4:1 ratio of cyclohexene to TBHP), the yield ofcyclohexene oxide in 12 h can get up to 65%.At last, in the oxidation reaction of benzyl alcohol by molecular oxygen, the heterogeneous dioxomolybdenum (VI) complex catalyst CPS-[MoO2(BAGL)2] havevery high catalytic activity and excellent catalytic selectivity. Under the mild conditionssuch as at ordinary pressure of dioxygen and at a lower temperature of 90℃, benzylalcohol can be transformed to benzaldehyde as a single product with a yield of 62%. Thesolvent porlarity effects on the catalytic activity of the catalyst CPS-[MoO2(BAGL)2]greatly. The stronger the polarity of the solvent, the higher the activity of the catalystCPS-[MoO2(BAGL)2] is and the higher the yield of benzaldehyde is. The catalystCPS-[MoO2(BAGL)2] has excellent cycle and reuse property.