Title

Light-Initiated C-H Activation via Net Hydrogen Atom Transfer to a Molybdenum(VI) Dioxo

Document Type

Article

Publication Date

11-9-2022

Abstract

MoOCl(bpy-Bu) () is shown to be a potent one-electron oxidant upon irradiation with 365 nm light in various solvents, while being a weak two-electron oxidant in the dark. Complex is characterized to activate various types of C-H bonds photochemically, including allylic and benzylic positions as well as alkanes and aldehydes. In all of these oxidations, ultimately forms a bimetallic Mo(V)/Mo(V) species with a μ-oxo ligand (). Depending on the substrate, the major organic product is identified as either an oxygenated or a C-C coupled (homodimerized) compound along with a minor chlorinated species. The product selectivity is proposed to be dependent upon the relative values between the bond dissociation enthalpy (BDE) of a potentially new C-OH bond within the product versus the BDE of a Mo-OH motif within a Mo(V)O(OH) intermediate. Based on this, we can estimate the BDE for Mo-OH to be 83-93 kcal/mol. Mechanistic studies suggest that the C-H activation occurs via a net hydrogen atom transfer (HAT) from occurring either asynchronously or via a stepwise electron-proton transfer (ET-PT) process. Complex is further demonstrated to reform dioxo in the presence of chemical oxidants.

Publication Source (Journal or Book title)

Journal of the American Chemical Society

First Page

20472

Last Page

20483

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