A series of fascinating diiron complexes featuring bridging NxHy ligands stabilized by tris(phosphine)borate ([PhB(CH2PR2)(3)] = [PhBP3R]) ligands have been characterized. Hydrazine activation by [PhBP3R]Fe-Me (R = Ph or cyclohexylmethyl) leads to diiron Fe-2(mu-eta(1):eta(1)-N2H4) (mu-eta(2):eta(2)-N2H2) complexes featuring both bridging hydrazine and hydrazido ligands. Thermolysis of {[PhBP23CHCy]Fe}(2)(mu-eta(1):eta(1)-N2H4) (mu-eta(2):eta(2)-N2H2) at 22 degrees C leads to a structurally unusual {[PhBP2CHCy]Fe}(2)(mu-eta(1):eta(1)-N2H2)(mu-NH2)(2) complex featuring bridging HN=NH and NH2- ligands. This contrasts with {[PhBP3Ph]Fe}(2)(mu-eta(1):eta(1)-N2H2)(mu-eta(2):eta(2)-N2H2), which can be chemically oxidized to produce either {[PhBP3Ph]Fe}(2)(mu-eta(1):eta(1)-N2H2)(mu-eta(2):eta(2)-N2H2) or {[PhBP3Ph]Fe}(2)(mu-NH)(2), depending on the conditions. The former product is the only known complex to contain bridging N2H2 ligands in each of their limiting states of oxidation (HN=NH vs HN-NH2-). The latter product constitutes the first example of a diiron Fe-2(mu-NH)(2) diamond-shaped core.