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 η6 -arene interaction and can be utilized as an FeI synthon (Ar L = 5-mesityl-1,9-(2,4,6-Ph3 C6 H2 )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(κ2 -N4 Ad2 ), undergoes intermolecular nitrene transfer to phosphine, abstracts H atoms from weak C-H bonds (1,4-cyclohexadiene, 2,4,6-t Bu3 C6 H2 OH) to afford ferrous amido product (Ar L)Fe(NHAd), and can mediate intermolecular C-H amination of toluene [PhCH3 /PhCD3 kH /kD : 15.5(3); PhCH2 D kH /kD : 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.