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

Reduction of previously reported ( Ar L)FeCl with potassium graphite furnished a low-spin ( S = 1/2) iron complex ( Ar L)Fe which features an intramolecular η 6 -arene interaction and can be utilized as an Fe I synthon ( Ar L = 5-mesityl-1,9-(2,4,6-Ph 3 C 6 H 2 )dipyrrin). Treatment of ( Ar L)Fe with adamantyl azide or mesityl azide led to the formation of the high-spin ( S = 5/2), three-coordinate imidos ( Ar L)Fe(NAd) and ( Ar L)Fe(NMes), respectively, as determined by EPR, zero-field 57 Fe Mössbauer, magnetometry, and single crystal X-ray diffraction. The high-spin iron imidos are reactive with a variety of substrates: ( Ar L)Fe(NAd) reacts with azide yielding a ferrous tetrazido ( Ar L)Fe(κ 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- t Bu 3 C 6 H 2 O H ) to afford ferrous amido product ( Ar L)Fe(NHAd), and can mediate intermolecular C–H amination of toluene [PhCH 3 /PhCD 3 k H / k D: 15.5(3); PhCH 2 D 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.