Computational Study of Formic Acid Dehydrogenation Catalyzed by AlIII-Bis(imino)pyridine

The mechanism of formic acid dehydrogenation catalyzed by the bis(imino)pyridine‐ligated aluminum hydride complex (PDI2−)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,HPDI)Al(OOCH)3 is the active catalyst for formic acid dehydrogenation. Given this, the catalytic cycle includes β‐hydride elimination of (H,HPDI)Al(OOCH)3 to produce CO2, and the formed (H,HPDI)Al(OOCH)2H mediates HCOOH to release H2. Aluminum–ligand cooperation: A DFT study of formic acid dehydrogenation by AlIII–bis(imino)pyridine complexes has been conducted to demonstrate the detailed mechanism.