Activation of Dinitrogen Promoted by Adsorption of C 6 H 6 on Fe 2 VC - Cluster Anions.

The introduction of organic ligands is one of the effective strategies to improve the stability and reactivity of metal clusters. Herein, the enhanced reactivity of benzene-ligated cluster anions FeVC(CH) with respect to naked FeVC is identified. Structural characterization suggests that CH is molecularly bound to the dual metal site in FeVC(CH). Mechanistic details reveal that the cleavage of N≡N is feasible in FeVC(CH)/N but hindered by an overall positive barrier in the FeVC/N system. Further analysis discloses that the ligated CH regulates the compositions and energy levels of the active orbitals of the metal clusters. More importantly, CH serves as an electron reservoir for the reduction of N to lower the crucial energy barrier of N≡N splitting. This work demonstrates that the flexibility of CH in terms of withdrawing and donating electrons is crucial to regulating the electronic structures of the metal cluster and enhancing the reactivity.