Functional Models for the Mono- and Di-nitrosyl Intermediates of FNORs: Semireduction versus Superreduction of NO,Journal of the American Chemical Society

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Functional Models for the Mono- and Di-nitrosyl Intermediates of FNORs: Semireduction versus Superreduction of NO
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-03-13 , DOI: 10.1021/jacs.9b13795
Manish Jana ₁ , Corey J. White ₂ , Nabhendu Pal ₁ , Serhiy Demeshko ₃ , Claudia Cordes (née Kupper) ₃ , Franc Meyer ₃ , Nicolai Lehnert ₂ , Amit Majumdar ₁

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The reduction of NO to N2O by flavodiiron nitric oxide reductases (FNORs) is related to the disruption of the defense mechanism in mammals against invading pathogens. The proposed mechanism for this catalytic reaction involves both non-heme mono- and dinitrosyl diiron(II) species as the key intermediates. Recently, we have reported an initial account for NO reduction activity of an unprecedented mononitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)(DMF)3](BF4)3 (1) with [FeII{FeNO}7] formulation (Jana et al., J. Am. Chem. Soc. 2017, 139, 14380-14383). Here we report the full account for the selective synthesis, characterization and reactivity of FNOR model complexes, which include a dinitrosyl diiron(II) complex, [Fe2(N-Et-HPTB)(NO)2(DMF)2](BF4)3 (2) with [{FeNO}7]2 formulation and a related, mixed-valent diiron(II, III) complex, [Fe2(N-Et-HPTB)(OH)(DMF)3](BF4)3 (3). Importantly, whereas complex 2 is able to produce 89% of N2O via a semireduced mechanism (1 equiv. of CoCp2 per dimer = 50% of NO reduced), complex 1, under the same conditions (0.5 equiv. of CoCp2 per dimer = 50% of NO reduced), generates only ~50% of N2O. The mononitrosyl complex therefore requires superreduction for quantitative N2O generation, which constitutes an interesting dichotomy between 1 and 2. Reaction products obtained after N2O generation by 2 using 1 and 2 eq. of reductant have been characterized by molecular structure determination and EPR spectroscopy. Despite several available literature reports on N2O generation by diiron complexes, this is the first case where the end products from these reactions could be characterized unambiguously, which clarifies a number of tantalizing observations about the nature of these products in the literature.

中文翻译：

FNOR 的单和二亚硝酰基中间体的功能模型：NO 的半还原与超还原

黄酮二铁一氧化氮还原酶 (FNORs) 将 NO 还原为 N2O，这与哺乳动物对入侵病原体的防御机制的破坏有关。该催化反应的拟议机制涉及作为关键中间体的非血红素单和二亚硝基二铁 (II) 物种。最近，我们报道了一种前所未有的单亚硝酰二铁 (II) 复合物 [Fe2(N-Et-HPTB)(NO)(DMF)3](BF4)3 (1) 与 [FeII{ FeNO}7] 公式（Jana 等人，J. Am. Chem. Soc. 2017, 139, 14380-14383）。在这里，我们报告了 FNOR 模型复合物的选择性合成、表征和反应性的完整说明，其中包括二亚硝基二铁 (II) 复合物 [Fe2(N-Et-HPTB)(NO)2(DMF)2](BF4) 3 (2) 具有 [{FeNO}7]2 配方和相关的混合价二铁 (II, III) 络合物，[Fe2(N-Et-HPTB)(OH)(DMF)3](BF4)3 (3)。重要的是，复合物 2 能够通过半还原机制产生 89% 的 N2O（每二聚体 1 当量 CoCp2 = 50% 的 NO 还原），而复合物 1 在相同条件下（每二聚体 0.5 当量 CoCp2 = 50 % 的 NO 减少），仅产生约 50% 的 N2O。因此，单亚硝基复合物需要超还原以定量生成 N2O，这构成了 1 和 2 之间有趣的二分法。使用 1 和 2 eq. 2 生成 N2O 后获得的反应产物。已通过分子结构测定和 EPR 光谱对还原剂进行了表征。尽管有一些关于二铁络合物生成 N2O 的文献报道，但这是第一次可以明确表征这些反应的终产物，

更新日期：2020-03-13

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