The reaction of 2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NITpPy) with sodium bis(cis-1,2-dicyano-1,2-ethylenedithiolato)iron(III) (Fe(mmt)(2)) in the presence of sulfuric acid leads to the deoxygenation of the nitronyl nitroxide and the formation of the corresponding imidazolinium zwitterionic coordination compound bis(cis-1,2-dicyano-1,2-ethylenedithiolato)[2-(p-pyridyl)-4,4,5,5-tetramethylimidazolinium]iron-(III). The iron coordination is quasi-square pyramidal. Mossbauer measurements show a splitting below 4 K of the high-temperature doublet to a system of two doublets reminiscent of a spin transition between a quartet and a doublet state.