posted on 2021-09-17, 18:37authored byGui-Duo Jiang, Zi-Yu Li, Li-Hui Mou, Sheng-Gui He
Inspired
by the fact that the active centers of natural nitrogenases
are polynuclear iron–sulfur clusters, the reactivity of isolated
iron–sulfur clusters toward N2 has received considerable
attention to gain fundamental insights into the activation of the
NN triple bond. Herein, a series of gas-phase iron–sulfur
cluster anions FexSy– (x = 1–8, y = 0–x) were prepared and their
reactivities toward N2 were investigated systematically
by mass spectrometry. Among the 44 investigated clusters, only Fe5S2– and Fe5S3– showed superior reactivity toward N2. Theoretical results revealed that N2 binds molecularly
to the iron sites of Fe5S2,3– in a common end-on coordination mode with an unprecedented back-donation
interaction from the localized d–d bonding orbitals of Fe–Fe sites to the π* antibonding
orbitals of N2. This is the first example to disclose the
significant contribution of the dual metal sites rather than the single
metal atom to N2 adsorption in the prevalent end-on binding
mode.