Asymmetrically coordinated Ru-O site facilitates H2 heterolytic cleavage for efficient green reductive amination of octanol to octylamine: A mechanistic investigation

The catalytic reductive amination of octanol exhibits a promising and environmentally friendly pathway for the synthesis of octylamine, a compound with significant applications in the bulk and fine chemical sectors. However, the complexity of this reaction lies in the necessity of a catalyst that can simultaneously facilitate both the dehydrogenation and hydrogenation steps, occurring during the reaction. Herein, we have addressed this issue by designing a Ru@TiOx/Mg9Al6Ti6Ox catalyst with Ru-Ru and Ru-O asymmetric coordination structure that leads to 100 % octanol conversion, 94.6 % octylamine selectivity and a turn over frequency of 73.41 h−1, while maintaining the same activity for 4 consecutive cycles. Those performances, firmly positioning our catalyst among the most advanced and efficient catalysts reported to date. Using EXAFS, in situ FTIR, kinetic isotope experiments, and DFT calculations, we proposed a mechanism where Ru-O coordination structure promote the heterolytic cleavage of H2, producing highly active H+/H- species that can achieve efficient hydrogenation without hindering the dehydrogenation process. This work not only provides a promising catalyst for industrial application, but presents a valuable catalyst design strategy that involves complex tandem dehydrogenation/hydrogenation reactions.