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 Fe 2 VC(C 6 H 6 ) - with respect to naked Fe 2 VC - is identified. Structural characterization suggests that C 6 H 6 is molecularly bound to the dual metal site in Fe 2 VC(C 6 H 6 ) - . Mechanistic details reveal that the cleavage of N≡N is feasible in Fe 2 VC(C 6 H 6 ) - /N 2 but hindered by an overall positive barrier in the Fe 2 VC - /N 2 system. Further analysis discloses that the ligated C 6 H 6 regulates the compositions and energy levels of the active orbitals of the metal clusters. More importantly, C 6 H 6 serves as an electron reservoir for the reduction of N 2 to lower the crucial energy barrier of N≡N splitting. This work demonstrates that the flexibility of C 6 H 6 in terms of withdrawing and donating electrons is crucial to regulating the electronic structures of the metal cluster and enhancing the reactivity.