Origin and Regioselectivity of Direct Hydrogen Atom Transfer Mechanism of C(sp3)-H Arylation by [W10O32]4-/Ni Metallaphotoredox Catalysis

Polyoxometalates (POMs) have a broad array of applied platforms with well-characterized catalysis including photocatalysis to achieve aliphatic C(sp(3))-H bond functionalization. However, the reaction mechanism of POMs in organic transformation remains unknown due to the complexity of POM structures. Here, a challenging [W10O32](4-)/Ni metallaphotoredox-catalyzed C(sp(3))-H arylation of alkane has been investigated by density functional theory (DFT) calculations. The calculation revealed that the superficial active center located in bridged oxygen of *[W10O32](4-) is responsible for the abstraction of a foreign hydrogen atom and the activation of a C(sp(3))-H bond. Furthermore, we discussed this activated process using the direct activation model of the C(sp(3))-H sigma-bond to deepen our mechanistic understanding of POM mediated C-H bond activation via the hydrogen atom transfer (HAT) pathway. Specifically, comparing three common mechanisms for nickel catalysis inducing by Ni-0, Ni-I, and Ni-II to construct a C-C bond, the nickel catalytic cycle induced by the Ni-I active catalyst is profitable in kinetics and thermodynamics. Finally, a radical mechanism merging the ([W10O32]4--*[W10O32](4-)- [HW10O32](4-)-[W10O32](4-)) decatungstate reductive quenching cycle, ([HW10O32](4-)-[H2W10O32](4-)-[HW10O32](4-)) electron relay, and (Ni-I-Ni-II-Ni-I-Ni-III-Ni-I) nickel catalytic cycle is proposed to be favorable. We hope that this work would provide a better understanding of the unique catalytic activity of decatungstate anions for the direct functionalization of the C(sp(3))-H bond.