Characterization of Structurally Unusual Diiron NxHy Complexes
摘要:
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.
Transformation of an [Fe(η2-N2H3)]+ Species to π-Delocalized [Fe2(μ-N2H2)]2+/+ Complexes
作者:Caroline T. Saouma、R. Adam Kinney、Brian M. Hoffman、Jonas C. Peters
DOI:10.1002/anie.201006299
日期:2011.4.4
monomeric Fe(η2‐N2H3) species has been prepared, and exposure to oxygen yields a diiron complex that features five‐coordinate iron centers and an activated bridging diazene ligand (see picture; C gray, N blue, Fe black, P red, O green). Structural, theoretical, and spectroscopic data for the redox pair [Fe2(μ‐N2H2)]2+/+ are consistent with 4‐center, 4‐electron π‐delocalized bonding across the Fe‐NH‐NH‐Fe