Monomeric Bis(anilido)iron(II) Complexes with N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Redox Reactivity toward Aryl Halides

Abstract

Using monodentate N-heterocyclic carbenes as the ancillary ligands, seven monomeric bis(anilido)iron(II) complexes [(IPr(2)Me(2))(2)Fe(NHAr)(2)] (IPr(2)Me(2) = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene; Ar = Ph, C(6)H(4)-2-Pr(i), Mes, C(6)H(3)-2,6-Cl(2), Dipp) and [(IPr)Fe(NHAr)(2)] (IPr = 2,5-di(2,6-diisopropylphenyl)imidazol-1-ylidene; Ar = C(6)H(3)-2,6-Cl(2), Dipp) have been prepared by the one-pot reactions of [Fe(Mes)(2)](2) with the corresponding N-heterocyclic carbenes, and anilines. These high-spin diamido complexes have been fully characterized by (1)H NMR, solution magnetic susceptibility, UV-vis, IR, X-ray diffraction, cyclic voltammetry, as well as elemental analysis. The strong affinity of the N-heterocyclic carbene ligands toward ferrous centers, and the steric protection exerted by the NHC ligands are the key factors to stabilize these bis(anilido)iron complexes in a monomeric manner. Reactivity studies revealed the four-coordinate complex [(IPr(2)Me(2))(2)Fe(NHMes)(2)] can react with 1 equiv of 1-iodo-3,5-dimethylbenzene or 1-bromo-3,5-dimethylbenzene in C(6)D(6) and THF-d(8) to furnish 1-C(6)D(5)-3,5-Me(2)C(6)H(3), and 5-D-1,3-Me(2)C(6)H(3), respectively. Under similar conditions, the three-coordinate compound [(IPr)Fe(NHDipp)(2)] is inert toward these halides.