Two transition-metal-modified Nb/W mixed-addendum polyoxometalates for visible-light-mediated aerobic benzylic C-H oxidations

The visible-light-induced selective oxidation of ubiquitous C-H bonds into valuable C=O bonds under aerobic conditions is one of the most attractive approaches for the construction of carbonyl-containing molecules. In this work, two transition metal-containing Nb/W mixed-addendum POMs dimers with the formula of K2Na2H5[(Fe(H2O)(4))(3)(P2W15Nb3O62)(2)]center dot 24H(2)O (POM[Fe]) and K2Na3H4[(Cr(H2O)(4))(3)(P2W15Nb3O62)(2)]center dot 32H(2)O (POM[Cr]) have been synthesized and characterized by various analytical and spectral techniques. POM[Fe] was proved to be an efficient photocatalyst for benzylic C-H oxidation under visible light and using oxygen as an oxidant to produce the corresponding carbonyl complex in good yields. A plausible mechanism involving superoxide radical was proposed for the catalytic reaction. POM[Fe] showed good reusability in the recycling experiments. IR spectroscopy and XRD analysis indicate that POM[Fe] can retain its integrity after catalysis. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

In this work, two transition metal-containing Nb/W mixed-addendum POM dimers were synthesized and characterized. POM[Fe] was proven to be an efficient photocatalyst for benzylic C-H oxidation under visible light and using oxygen as an oxidant. The results provide insights into the mechanism and effectiveness of POM[Fe] in the oxidation reaction.