In spite of the comprehensive study of the metal-mediated conversion of NO to N 2 O disclosing the conceivable processes/mechanism in biological and biomimetic studies, in this study, the synthesis cycles and mechanism of NO reduction to N 2 O triggered by the electronically localized dinuclear {Fe(NO) 2 } 10 −{Fe(NO) 2 } 9 dinitrosyl iron complex (DNIC) [Fe(NO) 2 (μbdmap)Fe(NO) 2 (THF)] (1) (bdmap = 1,3-bis(dimethylamino)-2-propanolate) were investigated in detail. Reductive conversion of NO to N 2 O triggered by complex 1 in the presence of exogenous •NO occurs via the simultaneous formation of hyponitritebound {[Fe 2 (NO) 4 (μ-bdmap)] 2 (κ 4 -N 2 O 2 )} (2) and [NO 2 ] − -bridged [Fe 2 (NO) 4 (μ-bdmap)(μ-NO 2 )] (3) (NO disproportionation yielding N 2 O and complex 3). EPR/IR spectra, single-crystal X-ray diffraction, and the electrochemical study uncover the reversible redox transformation of {Fe(NO) 2 } 9 -{Fe(NO) 2 } 9 [Fe 2 (NO) 4 (μ-bdmap)(μ-OC 4 H 8 )] + (7) ↔ {Fe(NO) 2 } 10 -{Fe(NO) 2 } 9 1 ↔ {Fe(NO) 2 } 10 -{Fe(NO) 2 } 10 [Fe(NO) 2 (μ-bdmap)Fe(NO) 2 ] − (6) and characterize the formation of complex 1. Also, the synthesis study and DFT computation feature the detailed mechanism of electronically localized {Fe(NO) 2 } 10 −{Fe(NO) 2 } 9 DNIC 1 reducing NO to N 2 O via the associated hyponitrite-formation and NO-disproportionation pathways. Presumably, the THF-bound {Fe(NO) 2 } 9 unit of electronically localized {Fe(NO) 2 } 10 -{Fe(NO) 2 } 9 complex 1 served as an electron buffering reservoir for accommodating electron redistribution, and the {Fe(NO) 2 } 10 unit of complex 1 acted as an electron-transfer channel to drive exogeneous •NO coordination to yield proposed relay intermediate κ 2 -N,O-[NO] − -bridged [Fe 2 (NO) 4 (μ-bdmap)(μ-NO)] (A) for NO reduction to N 2 O.

Flavodiiron nitric oxide reductases (FNORs) evolved in some pathogens are known to detoxify NO via two-electron reduction to N2O to mitigate nitrosative stress. In this study, we describe how the electronically localized {Fe­(NO)2}10-{Fe­(NO)2}9 dinuclear dinitrosyl iron complex (dinuclear DNIC) [(NO)2Fe­(μ-bdmap)­Fe­(NO)2(THF)] (2) (bdmap = 1,3-bis­(dimethylamino)-2-propanolate) can induce a reductive coupling of NO to form hyponitrite-coordinated tetranuclear DNIC, which then converts to N2O. Upon the addition of 1 equiv of NO into the dinuclear {Fe­(NO)2}10-{Fe­(NO)2}9 DNIC 2, the proposed side-on-bound [NO]−-bridged [(NO)2Fe­(μ-bdmap)­(κ2-NO) Fe­(NO)2] intermediate may facilitate intermolecular (O)­N–N­(O) bond coupling to yield the paramagnetic tetranuclear quadridentate trans-hyponitrite-bound {[(NO)2Fe­(μ-bdmap)­Fe­(NO)2]2(κ4-N2O2)} that transforms to [Fe­(NO)2(μ-bdmap)]2, along with the release of N2O upon Hbdmap (1,3-bis­(dimethylamino)-2-propanol) added.

A thiolate-bridged binuclear complex [PPN][(Mn(PS3))] (1, PPN = bis(triphenylphosphine)iminium and PS3H = (2,2',2″-trimercapto-3,3',3″-tris(trimethylsilyl)triphenylphosphine)), prepared from the reaction of MnCl/[PPN]Cl and Li[PS3], converts into a mononuclear complex [PPN][Mn(PS3)(DABCO)] (2) in the presence of excess amounts of DABCO (DABCO = 1,4-diazabicyclo[2.2.2]octane). Variable temperature studies of solution containing 1 and DABCO by UV-vis spectroscopy indicate that 1 and 2 exist in significant amounts in equilibrium and mononuclear 2 is favored at low temperature. Treatment of 1 or 2 with the monomeric O-side-on-bound [PPN][Mn(O)(PS3)] (3) produces the mono-oxo-bridged dimer [PPN][(Mn(PS3))(μ-O)] (4). The electrochemistry of 1 and 2 reveals anodic peak(s) for a MnMn redox couple at shifted potentials against Fc/Fc, indicating that both complexes can be oxidized by dioxygen. The O activation mediated by 1 and 2 is investigated in both solution and the solid state. Microcrystals of 2 rapidly react with air or dry O to generate the Mn(IV)-peroxo 3 in high yield, revealing a solid-to-solid transformation and two-electron reduction of O. Oxygenation of 1 or 2 in solution, however, is affected by diffusion and transient concentration of dioxygen in the two different substrates, leading to generation of 3 and 4 in variable ratios.