Highly Active and Sulfur-Tolerant Ruthenium Phosphide Catalyst for Efficient Reductive Amination of Carbonyl Compounds
Hiroya Ishikawa, Sho Yamaguchi, Tomoo Mizugaki, Takato Mitsudome
Abstract
The catalysis of precious metal phosphides in liquid-phase molecular transformations has rarely been explored. Herein, we reveal the remarkable performance of ruthenium phosphide nanoparticles supported on activated carbon (Ru 2 P/C) as a highly efficient heterogeneous catalyst for reductive amination of carbonyl compounds. Typically, Ru 2 P/C exhibited high activity for amination even under 1 bar of H 2 /NH 3 mixed gas, in sharp contrast to the conventional Ru catalysts that require high H 2 pressure (H 2 2.5–40 bar). Furthermore, Ru 2 P/C demonstrated versatility across aliphatic, aromatic, and heteroaromatic carbonyl compounds, providing the corresponding amines in high yields. Notably, Ru 2 P/C exhibited high tolerance toward sulfur-containing carbonyl compounds, known for their potential to strongly coordinate with metal active species, leading to deactivation. Comprehensive studies based on control experiments, kinetic studies, spectroscopic analyses, temperature-programmed desorption measurements, and evaluations of H 2 –D 2 exchange rates revealed that the multiple properties of Ru 2 P/C significantly contribute to its high catalytic efficiency. These properties encompassed its high H 2 -activation ability, the acidic property for the efficient formation of imine intermediates, and sulfur tolerance derived from the ensemble effect of the Ru–P bond formation.