Ligand Tailoring Toward an Air-Stable Iron(Ⅴ) Nitrido Complex

摘要

A new supporting ligand, tris-[2-(3-mesityl-imidazol-2-ylidene)methyl]-amine (TIMMN~(Mes)), 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)_3FeN]~(0/+). On the basis of~(57)Fe Moessbauer, 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.