The study investigates the mechanism of oxidative cobalt(salen) catalyzed hydrofunctionalization of alkenes, focusing on the role of cobalt(III) complexes and their reactions with silanes, oxidants, and solvents. Key findings include the identification of cobalt(III) aquo complexes as more active than cobalt(III) fluoride complexes in catalytic reactions. Water addition significantly enhances the catalytic reaction, enabling product formation in 2 hours at -50°C in acetone. Kinetic studies reveal that the turnover-limiting step involves cobalt(III) hydride formation, which is followed by hydrogen atom transfer (HAT) to the alkene. The cobalt(III) hydride degrades to release H+ through a bimetallic pathway, explaining the [Co]²+ dependence of the off-cycle reaction. The catalytic reaction follows a power law k_obs[Co][silane], with lower catalyst loading improving yield by reducing unproductive silane/oxidant consumption. The study highlights the importance of understanding cobalt-hydride and cobalt-alkyl complex mechanisms in oxidative MHAT reactions. The reaction mechanism involves the formation of a cobalt(III) alkyl intermediate, which is oxidized to cobalt(IV) and then attacked by a nucleophile to form the product. Kinetic studies show that the rate of the catalytic reaction is first-order in [Co] and [silane], with the turnover-limiting step being the formation of the cobalt(III) hydride. The study also demonstrates that the cobalt(III) aquo complex is the resting state of the catalyst, which is more stable than the cobalt(III) fluoride complex. The presence of water is crucial for the catalytic reaction, as it facilitates the formation of the cobalt(III) aquo complex and enhances the reaction rate. The study provides insights into the mechanistic details of oxidative MHAT reactions and lays the groundwork for understanding other catalytic reactions mediated by cobalt-hydride and cobalt-alkyl complexes.The study investigates the mechanism of oxidative cobalt(salen) catalyzed hydrofunctionalization of alkenes, focusing on the role of cobalt(III) complexes and their reactions with silanes, oxidants, and solvents. Key findings include the identification of cobalt(III) aquo complexes as more active than cobalt(III) fluoride complexes in catalytic reactions. Water addition significantly enhances the catalytic reaction, enabling product formation in 2 hours at -50°C in acetone. Kinetic studies reveal that the turnover-limiting step involves cobalt(III) hydride formation, which is followed by hydrogen atom transfer (HAT) to the alkene. The cobalt(III) hydride degrades to release H+ through a bimetallic pathway, explaining the [Co]²+ dependence of the off-cycle reaction. The catalytic reaction follows a power law k_obs[Co][silane], with lower catalyst loading improving yield by reducing unproductive silane/oxidant consumption. The study highlights the importance of understanding cobalt-hydride and cobalt-alkyl complex mechanisms in oxidative MHAT reactions. The reaction mechanism involves the formation of a cobalt(III) alkyl intermediate, which is oxidized to cobalt(IV) and then attacked by a nucleophile to form the product. Kinetic studies show that the rate of the catalytic reaction is first-order in [Co] and [silane], with the turnover-limiting step being the formation of the cobalt(III) hydride. The study also demonstrates that the cobalt(III) aquo complex is the resting state of the catalyst, which is more stable than the cobalt(III) fluoride complex. The presence of water is crucial for the catalytic reaction, as it facilitates the formation of the cobalt(III) aquo complex and enhances the reaction rate. The study provides insights into the mechanistic details of oxidative MHAT reactions and lays the groundwork for understanding other catalytic reactions mediated by cobalt-hydride and cobalt-alkyl complexes.