AbstractDinitrogen 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‐N2)Lbis]− (2), where [Lbis]− 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 Fe2N2 unit with D=−5.23 cm−1 and consequent slow magnetic relaxation.