<i>d</i>–<i>d</i> Orbital\nCoupling in RuCo Alloy Enhances the Ammonolysis of a Schiff Base in\nReductive Amination

The selective production of primary amines through reductive\namination\nhas received increasing attention due to their extensive applications,\nwhile efficient reductive amination is still challenging. Herein,\na novel strategy was developed to realize the efficient reductive\namination of carbonyl compounds with NH<sub>3</sub> via <i>d</i>–<i>d</i> orbital coupling strategies in RuCo alloys.\nThe designed series of RuCo alloy catalysts not only exhibited excellent\nperformance in conversion of various substrates but also demonstrated\nuniversal applicability across different supports. The key role of\nRuCo alloy is its unique ability to effectively catalyze the ammonolysis\nof a Schiff base, the rate-determining step in reductive amination.\nTheoretical studies reveal that the <i>d</i>–<i>d</i> orbital coupling strategies break the five <i>d</i> orbital equivalent contributions of metal (Co or Ru) atoms, and\nthe <i>d</i> orbitals primarily contribute through the <i>d</i><sub><i>z</i>2</sub> and <i>d</i><sub><i>x</i>2<i>‑y</i>2</sub> orbitals of\nRu and the <i>d</i><sub><i>z</i>2</sub> orbital\nof Co on the RuCo(001) surface, which significantly driving the homolytic\nNH<sub>3</sub> dissociation during the ammonolysis of the Schiff base.\nFurthermore, stable Co–H covalent bond species and RuCo-NH<sub>2</sub> half-ionic and half-covalent bond species on the RuCo(001)\nsurface were generated with lower energy levels. This work not only\nachieves efficient reductive amination but also provides an atomic\norbital-level understanding of the <i>d</i>–<i>d</i> orbital coupling strategies for heterogeneous catalysis.