High-Spin Iron Imido Complexes Competent for C-H Bond Amination

Reduction of previously reported (L-Ar)FeCl with potassium graphite furnished a low-spin (S = 1/2) iron complex (L-Ar)Fe which features an intramolecular eta(6)-arene interaction and can be utilized as an Fe-I synthon (L-Ar = 5-mesityl-1,9-(2,4,6-Ph3C6H2)dipyrrin). Treatment of (L-Ar)Fe with adamantyl azide or mesityl azide led to the formation of the high-spin (S = 5/2), three-coordinate imidos (L-Ar)Fe(NAd) and (L-Ar)Fe(NMes), respectively, as determined by EPR, zero-field Fe-57 Mossbauer, magnetometry, and single crystal X-ray diffraction. The high-spin iron imidos are reactive with a variety of substrates: (L-Ar)Fe(NAd) reacts with azide yielding a ferrous tetrazido (L-Ar)Fe(kappa(2)-N(4)Ad(2)), undergoes intermolecular nitrene transfer to phosphine, abstracts H atoms from weak C-H bonds (1,4-cyclohexadiene, 2,4,6-(Bu3C6H2OH)-Bu-t) to afford ferrous amido product (L-Ar)Fe(NHAd), and can mediate intermolecular C-H amination of toluene [PhCH3/PhCD3 k(H)/k(D): 15.5(3); PhCH2D k(H)/k(D): 11(1)] The C-H bond functionalization reactivity is rationalized from a two-step mechanism wherein each step occurs via maximal energy and orbital overlap between the imido fragment and the C-H bond containing substrate.