Theoretical Investigation into Selective Benzene Hydroxylation by Ruthenium-Substituted Keggin-Type Polyoxometalates

Benzene hydroxylation catalyzed by ruthenium-substituted Keggin-type polyoxometalates [Ru-V (O)XW11 O-39](n-) (Ru-V OX; X = Al, Ga, Si, Ge, P, As, S; heteroatoms; 3 <= n <= 6) is investigated using the density functional theory approach. As a possible side reaction, the water oxidation reaction is also considered. We found that the rate-determining step for water oxidation by (RuOX)-O-V requires a higher activation free energy than the benzene hydroxylation reaction, suggesting that all of the (RuOX)-O-V catalysts show high chemoselectivity toward benzene hydroxylation. Additionally, the heteroatom effect in benzene hydroxylation by (RuOX)-O-V is discussed. The replacement of Si by X induces changes in the bond length of mu O-4-X, resulting in a change in the activation free energy for benzene hydroxylation by (RuOX)-O-V, Consequentially, (RuOS)-O-V is expected to be the most effective catalyst among the ((RuOX)-O-V) catalysts for the benzene hydroxylation reaction.

Automated summary

The benzene hydroxylation catalyzed by ruthenium-substituted Keggin-type polyoxometalates was investigated, showing high chemoselectivity and the heteroatom effect on the reaction's activation free energy. Replacing Si with other elements can significantly affect the efficiency of the catalyst for benzene hydroxylation.