Reduction of Nitrite in an Iron(II)-Nitrito Compound by Thiols and Selenol Produces Dinitrosyl Iron Complexes via an {FeNO} Intermediate.

Reaction of an Fe(II) complex, [Fe(6-COO-tpa)] (), with PhE and NO produced [Fe(6-COO-tpa)(EPh)] (E = S, ; Se, ) and [Fe(6-COO-tpa)κO,O'-NO)] (), respectively (6-COOH-tpa is bis(2-pyridylmethyl)(6-carboxyl-2-pyridylmethyl)amine). Treatment of with 2 equiv of PhEH (E = S, Se) produced NO in ∼40% yields, respectively, along with and the DNICs, [Fe(EPh)(NO)] (E = S, Se). Treatment of with excess PhEH produced NO in similar yields, while was converted to the same DNICs and / (instead of ). The DNICs have been proposed to be generated via the reaction of PhE with an in situ generated, unstable {FeNO} intermediate, [Fe(6-COO-tpa)(NO)] (), which has also been synthesized separately. Compound reacts with PhS to generate [Fe(SPh)(NO)], thus supporting the proposed reaction pathway. Finally, while the treatment of two unique compounds, featuring inbuilt proton sources, [Fe(6-COO-tpa)(S-CH--COOH)] () and [Fe(6-COO-tpa)(S-CH--OH)] (), with 0.5 and 1 equiv of NO could produce NO only in 8-26% yields, treatment of with HS-CH--COOH and HS-CH--OH produced NO in much higher yields (65-77%). The combined results delineated the importance of coordination of NO for the proton-assisted reduction of NO to generate NO.