The molecular structure of a catalytically active key intermediate is determined in solution by employing 2D IR spectroscopy measuring vibrational cross-angles. The formate intermediate (2) in the formic acid dehydrogenation reaction catalyzed by a phosphorus-nitrogen PN3P-Ru catalyst is elucidated. Our spectroscopic studies show that the complex features a formate ion directly attached to the Ru center as a ligand, and a proton added to the imine arm of the dearomatized PN3P* ligand. During the catalytic process, the imine arms are not only reversibly protonated and deprotonated, but also interacting with the protic substrate molecules, effectively serving as the local proton buffer to offer remarkable stability with a turnover number (TON) over one million.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Y.Z. acknowledges a Schlumberger future faculty award. This work is supported by National Natural Science Foundation of China (NSFC) (NSFC-21627805, 21673004, and 21821004), NSF (CHE-1503865), and Ministry of Science and Technology of the People’s Republic of China (2017YFA0204702) (to J.Z.), and by King Abdullah University of Science and Technology (to K.-W.H.).