Recent advances in the chemistry of nitrogen fixation

Nitrogenase-mimic iron-containing chalcogels for photochemical reduction of dinitrogen to ammonia

“…Our DRIFTS results demonstrate that N 2 can bind to the chalcogel under light illumination. Upon initial formation of the M-N=N intermediates, electron and proton transfer can occur followed by additional light-induced electron reduction and protonation until the N≡N bond cleavage to NH 3 in the final step (5,39,40). The fact that NH 2 NH 2 is a far more active substrate than N 2 in yielding NH 3 explains why it is not detected as a product in our NMR spectra and suggests that NH 2 NH 2 is a likely intermediate similar to the mechanism postulated for nitrogenase itself (8,41).…”

On the feasibility of N 2 fixation via a single-site Fe I /Fe IV cycle: Spectroscopic studies of Fe I (N 2 )Fe I , Fe IV N, and related species

“…Among the various inorganic mechanisms for N 2 fixation that have been broadly considered, one interesting scenario is a Chatt-type N 2 reduction cycle (7) mediated by a single iron center. Indeed, such a scenario using a single metal center was proposed originally for the Mo site in the cofactor (7) and recently has been demonstrated for a Tris(amido)amine molybdenum system by Schrock and coworkers (8)(9)(10)(11)(12). For a related iron-mediated scheme (Fig.…”

Inner-sphere two-electron reduction leads to cleavage and functionalization of coordinated dinitrogen

“…Unfortunately, this problem is still unsolved. While much has been learned about how to synthesize dinitrogen complexes (hundreds are now known) (3)(4)(5)(6)(7) and how N 2 binds to one or more metal complexes (7)(8)(9), there are only a few reports of homogeneous systems that involve turnover of molecular nitrogen, and these systems are not efficient or broadly applicable (10,11).…”

“…By far the most well studied reaction for dinitrogen complexes is protonation (14), in an effort to try to model the nitrogenase enzymes (15)(16)(17)(18), which convert N 2 to ammonia (NH 3 ) catalytically. Surprisingly, what has been discovered is that the observed products, which can include NH 3 , hydrazine (H 2 NNH 2 ), or even liberated dinitrogen, depend on a number of factors: the choice of the central metal, the choice of the ancillary ligands, and the choice of the acid (3,11,14,19). Another extremely common, but unproductive, reactivity pattern for coordinated N 2 is displacement by other donors or reactants, which is particularly prevalent for late metal dinitrogen complexes.…”