PII.144 A DFT investigation of the mechanism of quinoline hydrogenation catalyzed by a (1,5-cyclooctadiene)rhodium(I) complex

Resumo

A detailed catalytic cycle for the hydrogenation of quinoline (Q) to 1,2,3,4-tetrahydroquinoline (THQ) catalyzed by a cationic rhodium complex containing a 1,5-cyclooctadiene (COD) ligand was computationally investigated by using DFT. It was found that the catalytically active species was [Rh(COD)(kN-Q)]+ and that the addition of the two dihydrogen molecules occurs through the initial coordination of dihydrogen forming h²-H₂ intermediates, followed by the subsequent hydride transfer to Q and DHQ ligands (migratory insertion and reductive elimination, respectively). Except the reductive elimination of the THQ product, all of the elementary steps of the catalytic cycle were reversible, which is an important point in connection with the hydrogen storage models. Our theoretical DFT calculations are consistent with the experimental results previously reported.