One-Electron Reduction of Constrained and Unsymmetric Diiron Dinitrogen Complexes

Iron sites in both nitrogenase enzymes and chemical catalysts for N2 fixation are typically at constrained distances and angles. Herein, we report a one -electron reduction reaction realized by constrained diiron dinitrogen cores. Using the semicircular bis (& beta;-diketiminate) ligand, a series of diiron dinitrogen complexes were synthesized, in which the N2 groups were allowed to bind with Fe-CtN2-Fe angles ranging from 154 & DEG; to 158 & DEG; (CtN2 = centroid of N2). One -electron reduction of complex 2a [LFe(& mu;-N2)Fe(Et2O)] gave dimer product 3a [LFe(& mu;-N2)FeK]2(& mu;-N2) or monomer 3b [LFe(& mu;-N2)Fe(DMAP)K]. Based on superconducting quantum interference device measurements and density functional theory calculations, 2a, 3a, and 3b exhibited ground spin states of S = 3, S = 5, and S = 5/2, respectively. In addition, complex 3 underwent N2 derivatization via a silylation pathway followed by an acidic cleavage to yield N2H4 as the product.