In this study, the gold clusters Au 11 (PPh 3 ) 7 Cl 3 and Au 11 (PPh 2 Py) 7 Br 3 (PPh 2 Py = diphenyl-2-pyridylphosphine) are synthesized via a one-pot procedure based on the wet chemical reduction method. The Au 11 (PPh 3 ) 7 Cl 3 cluster is found to be active in the chemoselective hydrogenation of 4-nitrobenzaldehyde in the presence of hydrogen (H 2 ) and a base (e.g., pyridine). Interestingly, the cluster with the functional ligand PPh 2 Py shows similar activity without losing catalytic efficiency in the absence of the base. The structure of the gold clusters and reaction pathway of the catalytic hydrogenation are investigated at the atomic/molecular level via UV–vis spectroscopy, electrospray ionization (ESI) mass spectrometry, and density functional theory (DFT) calculations. It is found that one ligand (PPh 3 or PPh 2 Py) removal is the first step to expose the core of the gold clusters to reactants, providing an active site for the catalytic reaction. Then, the H–H bond of the H 2 molecule becomes activated with the aid of either free amine (base) or ligand PPh 2 Py which is attached to the gold clusters. This work demonstrates the promise of the functional ligand PPh 2 Py in the catalytic hydrogenation to reduce the amount of materials (free base: e.g., pyridine) that ultimately enter the waste stream, thereby providing a more environmentally friendly reaction medium.
No takes yet. Share an insight, caveat, or question.
Liu et al. (2015) studied this question.