A Nonheme Mononuclear {FeNO}

A new nonheme iron(II) complex, Fe(II)(Me(3)TACN)((OSi(Ph2))(2)O) (1), is reported. Reaction of 1 with NO((g)) gives a stable mononitrosyl complex Fe(NO)(Me(3)TACN)((OSi(Ph2))(2)O) (2), which was characterized by Mössbauer (δ = 0.52 mm s(−1), |ΔE(Q)| = 0.80 mm s(−1)), EPR (S = 3/2), resonance Raman (RR) and Fe K-edge X-ray absorption spectroscopies. The data show that 2 is an {FeNO}(7) complex with an S = 3/2 spin ground state. The RR spectrum (λ(exc) = 458 nm) of 2 combined with isotopic labeling ((15)N, (18)O) reveals ν(N-O) = 1680 cm(−1), which is highly activated, and is a nearly identical match to that seen for the reactive mononitrosyl intermediate in the nonheme iron enzyme FDPnor (ν(NO) = 1681 cm(−1)). Complex 2 reacts rapidly with H(2)O in THF to produce the N-N coupled product N(2)O, providing the first example of a mononuclear nonheme iron complex that is capable of converting NO to N(2)O in the absence of an exogenous reductant.