Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Reduction of Nitrite in an Iron (II)-nitrito Compound by Thiols and Selenol Produces Dinitrosyl Iron Complexes via an {FeNO}7 Intermediate (#602)

SOUMIK KARMAKAR 1 , SUMAN PATRA 1 , RITAPRAVO HALDER 1 , SUCHISMITA KARMAKAR 1 , AMIT MAJUMDAR 1
  1. SCHOOL OF CHEMICAL SCIENCES, INDIAN ASSOCIATION FOR THE CULTIVATION OF SCIENCE, KOLKATA, WEST BENGAL, INDIA

Reaction of a Fe (II) complex, [Fe(6-COO⁻-tpa)]1+ (1) with PhE⁻ and NO2⁻ produced [Fe(6-COO⁻-tpa) (EPh)] (E = S, 2a; Se, 3) and [Fe(6-COO⁻-tpa) (κ2-O, O´-NO2)] (4), respectively (6-COOH-tpa is bis(2-pyridylmethyl) (6-carboxyl-2-pyridylmethyl) amine). Treatment of 4 with 2 equiv of PhEH (E = S, Se) produced NO in ~ 40% yields, respectively, along with 1 and the DNICs, [Fe(EPh)2(NO)2]1⁻ (E = S, Se). Treatment of 4 with excess PhEH produced NO in similar yields while 4 was converted to the same DNICs and 2a/3 (instead of 1). The DNICs have been proposed to generate via the reaction of PhE⁻ with an in situ generated, unstable {FeNO}7 intermediate, [Fe(6-COO⁻-tpa) (NO)]1+ (6), which has also been sythesized separately. Compound 6 reacts with PhS⁻ to generate [Fe(SPh)2(NO)2]1⁻, thus supporting the proposed reaction pathway. Finally, while the treatment of two unique compounds, featuring inbuilt proton sources, [Fe(6-COO⁻-tpa)(S-C6H4-p-COOH)] (7) and [Fe(6-COO⁻-tpa)(S-C6H4-o-OH)] (8), with 0.5 and 1 equiv of NO2⁻ could produce NO only in 8-26% yields, treatment of 4 with HS-C6H4-p-COOH and HS-C6H4-o-OH produced NO in much higher yields (65-77%). The combined results delineated the importance of the coordination of NO2⁻ for the proton-assisted reduction of NO2⁻ to generate NO. 

 

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