Characterization of Structurally Unusual Diiron NxHy Complexes

Abstract

A series of fascinating diiron complexes featuring bridging N(x)H(y) ligands stabilized by tris(phosphine)borate ([PhB(CH(2)PR(2))(3)] = [PhBP(R)(3)]) ligands have been characterized. Hydrazine activation by [PhBP(R)(3)]Fe-Me (R = Ph or cyclohexylmethyl) leads to diiron Fe(2)(mu-eta(1):eta(1)-N(2)H(4))(mu-eta(2):eta(2)-N(2)H(2)) complexes featuring both bridging hydrazine and hydrazido ligands. Thermolysis of {[PhBP(CH(2))(Cy)(3)]Fe}(2)(mu-eta(1):eta(1)-N(2)H(4))(mu-eta(2):eta(2)-N(2)H(2)) at 22 degrees C leads to a structurally unusual {[PhBP(CH(2))(Cy)]Fe}(2)(mu-eta(1):eta(1)-N(2)H(2))(mu-NH(2))(2) complex featuring bridging HN horizontal lineNH and NH(2)(-) ligands. This contrasts with {[PhBP(Ph)(3)]Fe}(2)(mu-eta(1):eta(1)-N(2)H(4))(mu-eta(2):eta(2)-N(2)H(2)), which can be chemically oxidized to produce either {[PhBP(Ph)(3)]Fe}(2)(mu-eta(1):eta(1)-N(2)H(2))(mu-eta(2):eta(2)-N(2)H(2)) or {[PhBP(Ph)(3)]Fe}(2)(mu-NH)(2), depending on the conditions. The former product is the only known complex to contain bridging N(2)H(2) ligands in each of their limiting states of oxidation (HN horizontal lineNH vs HN-NH(2-)). The latter product constitutes the first example of a diiron Fe(2)(mu-NH)(2) diamond-shaped core.