Testing the Push–Pull Hypothesis: Lewis Acid Augmented N2 Activation at Iron

摘要

We present a systematic investigation of the structural and electronic changes that occur in an Fe(0)–N2 unit (Fe(depe)2(N2); depe = 1,2-bis(diethylphosphino)-ethane) upon the addition of exogenous Lewis acids. Addition of neutral boranes, alkali metal cations, and an Fe²⁺ complex increases the N–N bond activation (Δ νNN up to 172 cm⁻¹), decreases the Fe(0)–N2 redox potential, polarizes the N–N bond, and enables −N protonation at uncommonly anodic potentials. These effects were rationalized using combined experimental and theoretical studies.