Computational Study of Formic Acid Dehydrogenation Catalyzed by Al III –Bis(imino)pyridine

The mechanism of formic acid dehydrogenation catalyzed by the bis(imino)pyridine‐ligated aluminum hydride complex (PDI 2− )Al(THF)H (PDI=bis(imino)pyridine) was studied by density functional theory calculations. The overall transformation is composed of two stages: catalyst activation and the catalytic cycle. The catalyst activation begins with O−H bond cleavage of HCOOH promoted by aluminum–ligand cooperation, followed by HCOOH‐assisted Al−H bond cleavage, and protonation of the imine carbon atom of the bis(imino)pyridine ligand. The resultant doubly protonated complex ( H,H PDI)Al(OOCH) 3 is the active catalyst for formic acid dehydrogenation. Given this, the catalytic cycle includes β‐hydride elimination of ( H,H PDI)Al(OOCH) 3 to produce CO 2 , and the formed ( H,H PDI)Al(OOCH) 2 H mediates HCOOH to release H 2 .