Study On Catalytic Oxidation Of Styrene By Cobalt Corroles

As catalysts,cobalt corroles complexes bearing different electronic features were mainly applied to the catalytic reduction of oxygen.It is well-known that Co(Ⅱ)porphyrins are an efficient catalysts for the oxidation of alkene,however,reports on cobalt corrole catalyzed oxidation reactions are rare,and the reaction mechanisms are ambiguous.In catalytic oxidation reaction,tert-butyl hydroperoxide(TBHP),m-chloroperbenzoic acid(m-CPBA),and iodosylbenzene(PhIO)are commemly employed as oxygen sources and various organic compounds as substrates.It has been reported that solvents and oxidants have great influence on catalytic oxidation.In this thesis,four cobalt(Ⅲ)corroles that differ in their electronic environments based on meso-substitution by pentafluorophenyl and phenyl groups were synthesized and characterized.The effect of solvents and oxidants on the activity of catalysts in the catalytic oxidation of styrene was investigated.The reaction mechanism has been discussed.The main content of this thesis is as follows:1.Four cobalt(Ⅲ)corroles bearing different number of pentafluorophenyl and phenyl groups were synthesized and characterized by elemental analysis,HR-MS,UV-Vis,NMR,XPS as well as cyclic voltammetry.The first investigation of cobalt corrles catalyzed oxidation of alkene was carried by using these synthesized cobalt complexes as catalysts and styrene as substrate.UV-Vis spectrum experimental results indicated that the cobalt corroles maintain trivalent in DMF,DMAc,DCM and CH3CN.2.Catalytic oxidation activity by these cobalt corroles using different oxidants were studied in CH3CN/PhI(OAc)2,respectively;Thus,the effect on the oxidation product distribution was investigated.The result shows that when using PhI(oAc)2 as oxidant and CH3CN as solvent,benzaldehyde was found to be the main product;the most electron deficient cobalt corroles exhibit the highest catalytic activity,namely,the most desirable catalyst.In the system F15C-Co/PhI(OAc)2,with different solvent viz.DMF,DMAc,DCM,CH3CN,the catalytic efficiency is the most ideal in CH3CN system.3.It turned out cobalt corroles exhibited good catalytic oxidation activity in acetonitrile.Benzaldehyde was detected as the main product when using PhI(OAc)2,TBHP,PhIO KHSO5,as oxidants.In contrast,styrene oxide was found to be the major product when using m-CPBA oxidant.Nearly no products could be found by using H2O2 oxidant.Among all tested oxidtants,The first investigation of cobthalt corrole catalyzed oxidation of alkene was conducted by using styrene as substrate.The best yield was obtained in acetonitrile solvent in the air with TBHP oxidant(96%yield based on oxidant,up to 96 TON).The difference for catalytic activity in different reactive systems suggests the catalytic mechanism depend on the reactive system.Possible catalytic oxidation pathway was also discussed based on the observations of UV-Vis and situ HR-MS as well as EPR changes of the catalytic system in the absence of substrate.