Dicopper Dioxygenase Model Immobilized In Mesoporous Silica Nanoparticles For Toluene Oxidation: A Mechanism To Harness Both O Atoms Of O-2 For Catalysis

Recently, we have reported on a dicopper system (Cu-III(mu-O)(2)Cu-III complex immobilized in mesoporous silica nanoparticles) that can mediate the catalytic conversion of toluene into benzaldehyde by O-2, in which the oxidizing power of both O atoms is harnessed for catalytic turnover. This is the first example of a (Cu-III(mu-O)(2)Cu-III complex capable of functioning like a "dioxygenase" in hydrocarbon oxidation. We have undertaken a mechanistic study to clarify how this catalytic conversion is accomplished without the input of sacrificial reductants. While the first O atom in the (Cu-III(mu-O)(2)Cu-III complex can actively insert into a C-H bond, the second O atom left in the (Cu-III(mu-O)(2)Cu-III complex is inert. We show that a second molecule of O-2 is involved in activating the dicopper catalyst, forming an O-2 complex with the (Cu-III(mu-O)(2)Cu-III intermediate to give a species with the [Cu2O3](2+) core, which then mediates the transfer of the remaining O atom of the original O-2 molecule to the organic substrate to complete the catalytic turnover. The study offers a mechanistically characterized analogue of the heterogeneous mechanism at metal oxide catalyst that oxidizes organic substrates with the lattice oxygens by the Mars-van-Krevelen (MvK) significantly higher temperatures.