Toward Designing Reactive Metal Clusters for Dinitrogen Activation: A Guideline Based on N Initial Adsorption.

Gas-phase metal clusters are ideal models to explore transition-metal-mediated N activation mechanism. However, the effective design and search of reactive clusters in N activation are currently hindered by the lack of clear guidelines. Inspired by the Sabatier principle, we discovered in this work that N initial adsorption energy (Δ) is an important parameter to control the N activation reactivity of metal clusters in the gas phase. This mechanistic insight obtained from high-level calculations rationalizes the N activation reactivity of many previously reported metal clusters when combined with the known factor determining the N≡N cleavage process. Furthermore, based on this guideline of Δ, we successfully designed several new reactive clusters for cleaving N≡N triple bond under mild conditions, including FeVS, TaVC, and TaVC, the high N activation reactivity of which has been fully corroborated in our gas phase experiments employing mass spectrometry with collision-induced dissociation. The importance of Δ revealed in this work not only reshapes our understanding of N activation reactions in the gas phase but also could have implication for other N activation processes in the condensed phase. The more general establishment of this new perspective on N activation reactivity warrants future experimental and computational studies.