Effects of Secondary Sphere Hydrogen Bonds on Non-heme Iron Mediated Nitrite Reduction and Fe(III)2(μ-O)2 cores

A non-heme iron complex bearing a ligand with secondary sphere hydrogen bond (H-bond) donors, (tris(6-phenylaminopyridylmethyl)amine, TPANHPhFe(II), reduces nitrite (NO2-) to nitric oxide (NO) in the absence of H+donors, pro-ducing a dimeric Fe(III)2(μ-O)2 diamond core. The electronically analogous complex without H-bonds (tris(6-methylpyridylmethylamine), TPAMeFe(II) provides identical reactivity to also reduce NO2- to NO and produce an Fe(III)2(μ-O)2 core, but it is approximately four orders of magnitude slower than TPANHPhFe(II). This highlights the key roles of H-bonds to promote NO2- reduction. Further, we detail the structural and spectroscopic differences of the two Fe(III)2(μ-O)2 complexes to provide insight into the effects that H-bonding interactions have on Fe2O2 cores.