Dinitrogen Coordination to a High‐Spin Diiron(I/II) Species

Source abstract

Abstract Dinitrogen coordination to iron centers underpins industrial and biological fixation in the Haber–Bosch process and by the FeM cofactors in the nitrogenase enzymes. The latter employ local high‐spin metal centers; however, iron–dinitrogen coordination chemistry remains dominated by low‐valent states, contrasting the enzyme systems. Here, we report a high‐spin mixed‐valent cis ‐( μ ‐1,2‐dinitrogen)diiron(I/II) complex [(FeBr) 2 ( μ ‐N 2 ) L bis ] − ( 2 ), where [ L bis ] − is a bis(β‐diketiminate) cyclophane. Field‐applied Mössbauer spectra, dc and ac magnetic susceptibility measurements, and computational methods support a delocalized S = 7 / 2 Fe 2 N 2 unit with D =−5.23 cm −1 and consequent slow magnetic relaxation.