A five-coordinate phosphino/acetate iron(II) scaffold that binds N2, N2H2, N2H4, and NH3 in the sixth site.

A family of iron(II) complexes that coordinate dinitrogen, diazene, hydrazine, and ammonia are presented. This series of complexes is unusual in that the complexes within it feature a common auxiliary ligand set and differ only by virtue of the nitrogenous N(x)H(y) ligand that occupies the sixth binding site. The ability of an iron center to bind N(2), N(2)H(2), N(2)H(4), and NH(3) is important to establish in the context of evaluating catalytic N(2) reduction schemes that invoke these nitrogenous species. Such a scenario has been proposed as an iron-mediated, alternating reduction scheme within the cofactor of nitrogenase enzymes.