Radical Mechanism of Ir ^III /Ni ^II -Metallaphotoredox-Catalyzed C(sp ³ )–H Functionalization Triggered by Proton-Coupled Electron Transfer: Theoretical Insight

Abstract

Photoredox catalysis can be induced to activate organic substrates or to modulate the oxidation state of transition-metal catalysts via unique single-electron transfer processes, so as to achieve challenging C(sp 3 )−H functionalization under mild conditions. However, the specific reaction mechanism and relevant electron transfer process still need to be clarified. Here, a highly regioselective Ir III /Ni II -metallaphotoredox catalyzed hydroalkylation of unsymmetrical internal alkyne with ether α-hetero C(sp 3 )−H bond has been investigated by density functional theory (DFT) calculations. A novel radical mechanism was predicted to merge oxidative quenching (Ir III −*Ir III −Ir IV −Ir III ) and nickel catalytic cycles (Ni II −Ni III −Ni I −Ni III −Ni II ) for this C(sp 3 )−H functionalization to construct C(sp 3 )−C(sp 2 ) bond. It consists of seven major steps: the singleelectron transfer involved in the photoredox cycle for generating active Ni(I)−chloride complex,

Theoretical insight into decatungstate photocatalyzed alkylation ofN-tosylimineviahydrogen atom transfer and proton-coupled electron transfer

“…In recent years, the reaction mechanism of photo-redox catalysis has been systematically studied through experimental and theoretical methods. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Nonetheless, two important issues involved in the reaction remain obscure: (i) Is the C(sp 3 )-H activation of 1 by excited decatungstate realized by a general stepwise PCET or direct HAT process? (ii) What is the origin of regioselectivity of radical addition?…”

Theoretical Insight into the Multiple Roles of LiHMDS in Pd-Catalyzed Borylation of Fluorobenzene

“…The Stuttgart–Dresden–Bonn basis sets were employed for valence electrons of Pd atoms with corresponding effective core potentials representing their core electrons, and 6-31G­(d) basis sets were employed for other atoms. The solvation effect (toluene) was evaluated with the polarizable continuum model (PCM). − We also compared the PCM model with the solvation model based on density (SMD), as described in page S6 and Table S6 of the SI and found that the barrier of Ph–F bond activation in the SMD model differs little with that in the PCM model. We also made benchmark calculations on basis set as shown in SI.…”

Halide Non-Innocence and Direct Photo-Reduction of Ni(II) Enables Coupling of Aryl Chlorides in Dual Catalytic, Carbon-Heteroatom Bond Forming Reactions

“…In contrast, while oxidative quenching cycles (Fig. 1D) have been proposed in the literature occasionally with regards to Ni/PC dual catalytic C─C, C─O, C─N, or C─S bond forming systems, sometimes with computational support, [17][18][19][20][21] experiments capable of distinguishing between oxidative quenching, reductive quenching, and energy transfer (see reviews for relevant spectroscopic and electrochemical methods) [22][23][24] have not been performed in the study of these systems.…”