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Organometallic reaction selectivity is governed by dynamic motion rather than transition states or spin crossover. 

A novel and highly diastereoselective NBS-mediated cyclization ofN-alkoxy α,β-unsaturated silyl imino ethers to furnish nearly three dozen α-bromoN-alkoxy β-lactams with dual functional handles is described. 

We have explored the ligand topology of high-valent Fe(iv)–oxo complexes for screening a large molecular database with machine learning. 

Abstract Activation of the dinitrogen triple bond is a crucial step in the overall fixation of atmospheric nitrogen into usable forms for industrial and biological applications. Current synthetic catalysts incorporate metal ions to facilitate the activation and cleavage of dinitrogen. The high price of metal‐based catalysts and the challenge of catalyst recovery during industrial catalytic processes has led to increasing interest in metal‐free catalysts. One step toward metal‐free catalysis is the use of frustrated Lewis pairs (FLPs). In this study, we have examined 18 functionalized carbenes as FLPs to elucidate the influence of steric and electronic effects on the activation of dinitrogen. To test the effects of functionalization on dinitrogen activation, we have performed density functional theory (DFT), multireference, non and extended transition state‐natural orbital for chemical valence (ETS‐NOCV) calculations. Our results suggest that functional groups which introduce strong electron‐withdrawing effects and/or engage in extended π/π* systems lead to the lowering of the dissociation energy of the dinitrogen bond, which further contributes to greater nitrogen activation. We conjecture that these effects are due to enhanced back‐bonding capability of the p orbital of the carbene carbon atoms to the adjacent nitrogen atoms (increasing Lewis basicity of the carbene carbon atom) and enhanced stability of dissociated products. Our concluding remarks include opportunities to extend this activation study to explore the entire catalytic cycle with promising functionalized carbenes for experimental evaluation. 

High-valent Fe( iv )-oxo species have been found to be key oxidizing intermediates in the mechanisms of mononuclear iron heme and non-heme enzymes that can functionalize strong C–H bonds. Biomimetic Fe( iv )-oxo molecular complexes have been successfully synthesized and characterized, but their catalytic reactivity is typically lower than that of the enzymatic analogues. The C–H activation step proceeds through two competitive mechanisms, named σ- and π-channels. We have performed high-level wave function theory calculations on bare FeO 2+ and a series of non-heme Fe( iv )-oxo model complexes in order to elucidate the electronic properties and the ligand field effects on those channels. Our results suggest that a coordination environment formed by a weak field gives access to both competitive channels, yielding more reactive Fe( iv )-oxo sites. In contrast, a strong ligand environment stabilizes only the σ-channel. Our concluding remarks will aid the derivation of new structure–reactivity descriptors that can contribute to the development of the next generation of functional catalysts.