Heterolytic H_2 Activation Mediated by Low-Coordinate L_3Fe-(µ-N)-FeL_3 Complexes to Generate Fe(µ-NH)(µ-H)Fe Species

The diiron μ-nitride complexes, {L_3Fe^(II)(μ-N)Fe^(II)L_3}- and L_3Fe^(III)(μ-N)Fe^(II)L_3, heterolytically activate hydrogen (1 atm) at ambient temperature in solution (L_3 = [PhB(CH_2PPh_2)_3]-). These transformations lead to structurally unique {L_3Fe^(II)(μ-NH)(μ-H)Fe^(II)L^3}- and L_3Fe^(III)(μ-NH)(μ-H)Fe^(II)L_3 products. X-ray data establish a marked reduction in the Fe−Fe distance upon H_2 uptake, and spectroscopic data establish both Fe^(II)Fe^(II) species to be diamagnetic, whereas the Fe^(III)Fe^(II) species, L_3Fe^(III)(μ-N)Fe^(II)L_3 and L_3Fe^(III)(μ-NH)(μ-H)Fe^(II)L_3, populate doublet ground states with thermally accessible higher spin states