Journal of the American Chemical Society, Vol.143, No.3, 1458-1465, 2021
Ligand Tailoring Toward an Air-Stable Iron(V) Nitrido Complex
A new supporting ligand, tris-[2-(3-mesityl-imidazol-2-ylidene)methyl]-amine (TIMMNMes), was developed and utilized to isolate an air-stable iron(V) complex bearing a terminal nitrido ligand, which was synthesized by one-electron oxidation from the iron(IV) precursor. Single-crystal X-ray diffraction analyses of both complexes reveal that the metal-centered oxidation is escorted by iron nitride (Fe N) bond elongation, which in turn is accompanied by the accommodation of the high-valence iron center closer to the equatorial plane of a trigonal bipyramid. This contrasts with the previous observation of the only other literature- known Fe(IV) N/ Fe(V).N redox pair, namely, [PhB-((tBu)Im)(3)FeN](0/+). On the basis of Fe-57 Mossbauer, EPR, and UV/vis electronic absorption spectroscopy as well as quantum chemical calculations, we identified the lesser degree of pyramidalization around the iron atom, the Jahn-Teller distortion, and the resulting nature of the SOMO to be the decisive factors at play.