Selective oxidation of ethylbenzene by dioxygen. The effect of chelate center on catalysis by bicyclic nickel complexes

Abstract

The effect of the nature of the chelate center in Ni n complexes on their catalytic activity in the selective oxidation of ethylbenzene by dioxygen to a-phenylethyl hydroperoxide in the presence of nickel bis(acetylacetonate) (chelate center Ni(O,O)2 ) and nickel bis(eaaminoacetonate) (chelate center Ni(O,NH)2 ) was studied. The efficiency of selective oxidation of ethylbenzene increases substantially in the presence of the chelate with the Ni(O,NH)2 active center as a catalyst, which is mainly due to the transformation of the catalyst into more active species during the oxidation process. The mechanism of transformation of nickel bis(enaminoacetonate) under the action of dioxygen was suggested. The sequence of formation of the reaction products at different stages of the catalytic process was determined. The activity of the nickel complex with the Ni(O,NH)2 chelate center and the products of its transformation in the elementary stages of chain oxidation of ethylben,zene is discussed.

Engineering Aspects of Industrial Liquid-Phase Air Oxidation of Hydrocarbons

“…The use of phase-transfer catalysis in enhancing air oxidation of hydrocarbons has received attention. Matienko and co-workers [172][173][174][175] have studied a number of related issues, in connection with the oxidation of ethylbenzene. These authors carried out the liquidphase oxidation of ethyl benzene with Ni(acac) 2 as a catalyst.…”

Alkane Oxygenation with Hydrogen Peroxide Catalysed by Soluble Derivatives of Nickel and Platinum

“…1 Recently we have described alkane oxidations by systems based on derivatives of manganese, 2 vanadium, 3 osmium, 4 chromium 5 and gold. 6 Although nickel complexes were used as catalysts in oxidations of olefins, 7 ketones, 8 ethers, 9 dye amaranth 10 and ethylbenzene 11 only a few examples of alkane oxidations catalysed by nickel-containing systems 12 as well as aliphatic hydroxylation by a bis(µ-oxo)dinickel(III) complex 13 have been published. Epoxidation of alkenes was promoted by various nickel(II) complexes of macrocyclic ligands (e.g., cyclam).…”