Next, we sought to test 6 for the ability to bind N2 at low temperatures using variabletemperature UV-visible spectroscopy. Negligible spectral changes were observed between 25 and -100 °C in THF, Et2O, or toluene (Figure ). Addition of stoichiometric amounts of 18crown-6 slightly shifted the absorption maxima, but the resulting species also did not exhibit notable temperature-dependent spectral changes (Figure ). Thus, it does not appear that 6 undergoes speciation changes or N2 binding at these concentrations and temperatures. Further reduction of the iron(II) tetrameter 6 led to a silent NMR spectrum and a broad, featureless UV-Vis spectrum. The products formed in this reaction are unknown, and attempts to isolate or identify the species present were unsuccessful.