Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States.
Inorg Chem. 2021 Nov 1;60(21):15910-15917. doi: 10.1021/acs.inorgchem.1c01328. Epub 2021 Jun 28.
Iron-sulfur clusters (Fe-S) have been well established as a target for nitric oxide (NO) in biological systems. Complementary to protein-bound studies, synthetic models have provided a platform to study what iron nitrosylated products and byproducts are produced depending on a controlled reaction environment. We have previously shown a model [2Fe-2S] system that produced a dinitrosyl iron complex (DNIC) upon nitrosylation along with hydrogen sulfide (HS), another important gasotransmitter, in the presence of thiol, and hypothesized a similar reactivity pattern with [4Fe-4S] clusters which have largely produced inconsistent reaction products across biological and synthetic systems. Roussin's black anion (RBA), [Fe(μ-S)(NO)], is a previously established reaction product from synthetic [4Fe-4S] clusters with NO. Here, we present a new reactivity for the nitrosylation of a synthetic [4Fe-4S] cluster in the presence of thiol and thiolate. [EtN][FeS(SPh)] () was nitrosylated in the presence of excess PhSH to generate HS and an "RBA-like" intermediate that when further reacted with [NEt][SPh] produced a {Fe(NO)} DNIC, [EtN][Fe(NO)(SPh)] (). This "RBA-like" intermediate proved difficult to isolate but shares striking similarities to RBA in the presence of thiol based on IR υ stretching frequencies. Surprisingly, the same reaction products were produced when the reaction started with RBA and thiol. Similar to /NO, RBA in the presence of thiol and thiolate generates stoichiometric amounts of DNIC while releasing its bridging sulfides as HS. These results suggest not only that RBA may not be the final product of [4Fe-4S] + NO but also that RBA has unprecedented reactivity with thiols and thiolates which may explain current challenges around identifying biological nitrosylated Fe-S clusters.
铁硫簇 (Fe-S) 已被证实是生物系统中一氧化氮 (NO) 的靶标。与蛋白质结合研究相辅相成的是，合成模型为研究在受控反应环境下会产生哪些铁亚硝酰化产物和副产物提供了一个平台。我们之前展示了一个模型 [2Fe-2S] 系统，在存在巯基的情况下，该系统在亚硝酰化时会产生二亚硝酰铁配合物 (DNIC) 和另一种重要的气体递质硫化氢 (HS)，并假设 [4Fe-4S] 簇具有类似的反应性模式，而 [4Fe-4S] 簇在生物和合成系统中产生的反应产物则大相径庭。Roussin 黑阴离子 (RBA)，[Fe(μ-S)(NO)]，是以前在存在 NO 的情况下从合成 [4Fe-4S] 簇中产生的反应产物。在这里，我们提出了一种在存在巯基和硫醇盐的情况下对合成 [4Fe-4S] 簇进行亚硝酰化的新反应性。在过量 PhSH 的存在下，[EtN][FeS(SPh)] () 被亚硝酰化，生成 HS 和一个“RBA 样”中间体，当进一步与 [NEt][SPh] 反应时，生成 {Fe(NO)} DNIC，[EtN][Fe(NO)(SPh)] ()。该“RBA 样”中间体难以分离，但基于 IR υ 伸缩频率，在存在巯基的情况下与 RBA 具有惊人的相似性。令人惊讶的是，当反应从 RBA 和巯基开始时，会产生相同的反应产物。与 /NO 类似，在存在巯基和硫醇盐的情况下，RBA 生成等摩尔量的 DNIC，同时释放其桥接硫作为 HS。这些结果不仅表明 RBA 可能不是 [4Fe-4S] + NO 的最终产物，而且表明 RBA 与巯基和硫醇盐具有前所未有的反应性，这可能解释了当前在鉴定生物亚硝酰化 Fe-S 簇方面面临的挑战。
