Design of Manganese Phenol Pi‐complexes as Shvo‐type Catalysts for Transfer Hydrogenation of Ketones.

Catalytic hydrogenation is one of the most important reactions both in academic research and industry. We explored ability of the manganese pi‐complexes to act as Shvo‐type catalysts for transfer hydrogenation of ketones. DFT calculations suggested that the transfer of hydrogen atoms from the hypothetical intermediate [(C6Me3H2OH)Mn(CO)2H] to acetone has low activation barrier of 10.9 kcal mol−1. Experimentally a number of ketones with various functional groups (OMe, NH2, Cl, CF3, pyridyl) were successfully reduced in isopropanol at 90 °C in the presence of the complex [(C6Me3H2OH)Mn(CO)3]BF4 (1 mol %) and tBuOK (75 mol %). However, further investigation revealed that the reduction was mainly promoted by base rather than the manganese complex. Isolobal analogy: Phenol manganese pi‐complexes were proposed as possible Shvo‐type catalysts for transfer hydrogenation of ketones. DFT calculations suggested the reaction can proceed via transfer of hydrogen atoms from the intermediate [(C6Me3H2OH)Mn(CO)2H] to a ketone. A number of ketones were reduced in isopropanol at 90 °C in the presence of the complex [(C6Me3H2OH)Mn(CO)3]BF4 (1 mol %) and tBuOK (75 mol %). However, further investigation revealed that the reduction was mainly promoted by base rather than the manganese complex. [ABSTRACT FROM AUTHOR]