Reaction Mechanism and Kinetics study on Addition of CCl4 to 1-hexene Catalyzed by Mo-Mo Quintuply-bond

Transition metal-catalyzed atom transfer radical addition (ATRA) reactions are an effective and versatile strategy for constructing carbon-carbon bonds in organic synthesis. Typically, the metal center in this metal-assisted radical transformation undergoes a reversible redox process. In this work, a quintuply-bonded dinuclear complex, Mo-2((NN)-N-perpendicular to)(2) {(NN)-N-perpendicular to = mu-kappa(2)-CH[N(2,6-iPr(2)C(6)H(3))](2)}, has been investigated as potential catalyst for radical addition of CCl4 to 1-hexene by performing density functional theory (DFT) calculations. The study shows that the Mo-2((NN)-N-perpendicular to)(2)-mediated radical addition reaction is computationally predicted to occur with acceptable activation energies, indicating that the Mo-Mo quintuple bond can be applied as an effective catalyst for this transformation under mild conditions. The whole reaction involves 3 steps, two of which are metal-mediated. Firstly, the C-Cl bond activiation catalyzed by Mo-2((NN)-N-perpendicular to)(2) to obtain Mo-2((NN)-N-perpendicular to)(2)Cl and center dot CCl3 radical; Then the center dot CCl3 radical interacts with 1-hexene to get an addition, the addition product reacts with the Mo-2((NN)-N-perpendicular to)(2)Cl to get the last product and regenerate the catalyst Mo-2((NN)-N-perpendicular to)(2). Both the thermodynamic and kinetic study show that the second step is the rate-determine step. When coordinating solvent pyridine is added to the catalytic reaction, the reaction is suppressed due to their high energies barriers, which is consistent with experimental results.