Synergetic oxidation of ethylbenzene to acetophenone catalyzed by manganese(II) complexes bearing pendant iodophenyl groups

摘要

AbstractFive tetradentate ligands,L1–5, bearing the moiety of bis(pyridin-2-ylmethyl)amine (1) and their complexes with Mn(II) were prepared. All the compounds and metal complexes were appropriately characterized. The five manganese(II) complexes (3a–e) are of the formula, [Mn(II)LxCl2] (x?=?1-5), as suggested by the crystal structure of complexes3band3c. All the ligands except forL3possess two iodobenzene groupsviaan ether linkage (except forL1) with various lengths. By using oxone as an oxidant, the catalytic activity of these complexes on the oxidation of ethylbenzene to acetophenone in acetonitrile/water at room temperature was studied. Our results showed that the pendant iodophenyl groups play a synergetic role with the metal center in the catalysis, and complex3bpossesses the most appropriate length of the linkage between the iodobenzene group and the metal center. EPR and FTIR data suggest that the metal center of the active species should be Mn(IV) after the oxidation of oxone under the reaction conditions. A catalytic mechanism was also proposed based on the experimental observations.展开▼