A Nonheme Mononuclear {FeNO}⁷ Complex that Produces N₂O in the Absence of an Exogenous Reductant

Abstract

A new nonheme iron(II) complex, FeII(Me3TACN)((OSiPh2)2O) (1), is reported. Reaction of 1 with NO(g) gives a stable mononitrosyl complex Fe(NO)(Me3TACN)((OSiPh2)2O) (2), which was characterized by Mössbauer (δ=0.52 mm s−1, |ΔEQ|=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 (λexc=458 nm) of 2 combined with isotopic labeling (15N, 18O) 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 H2O in THF to produce the N‐N coupled product N2O, providing the first example of a mononuclear nonheme iron complex that is capable of converting NO to N2O in the absence of an exogenous reductant.

Reversible C–C Bond Formation, Halide Abstraction, and Electromers in Complexes of Iron Containing Redox-Noninnocent Pyridine-imine Ligands

“…On the basis of bond lengths, 46 the S T = 1/2 complex calculated for Fe2 (Table 1) is assigned to the δ = 0.477(3) mm/s doublet with ΔE Q = 1.077(6) mm/s (Γ = 0.295(8) mm/s). A broader 47,48 which is likely to be revealed in the higher-spin electromer with its longer bond distances. The relative areas of the S = 1/2 to S = 3/2 signals are roughly 60:40, and the data have been reproduced with an independently prepared sample, whose parameters are given in Table 2.…”