Formation of a Nitrogenase P-cluster [Fe_8S_7] Core via Reductive Fusion of Two All-Fenic [Fe_4S_4] Clusters
Formation of a Nitrogenase P-cluster [Fe_8S_7] Core via Reductive Fusion of Two All-Fenic [Fe_4S_4] Clusters
复制标题
通过两个全 Fenic [Fe_4S_4] 簇的还原融合形成固氮酶 P 簇 [Fe_8S_7] 核心
DOI：
10.1002/asia.201200568
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
K. Tatsumi
中科院分区：
文献类型：
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作者：
Y. Ohki;K. Tanifuji;N. Yamada;K. Tatsumi
铁硫团簇在电子转移蛋白中普遍存在，[1]和立方[Fe4S4]核心具有热力学稳定性，表现出多种氧化态，仅发生微小的几何变化。虽然从[Fe4S4]核中去除铁原子或硫原子在化学上是困难的，[2-4][Fe4S4]簇和[Fe3S4]簇之间的可逆转变被认为是在生理条件下发生的此外，在大气中二氮还原为氨的电子传递序列中起重要作用的氮酶p簇核心[Fe8S7]（图1）[6]被认为是通过两个[Fe4S4]簇的融合而组装的由于p -簇核心比两个[Fe4S4]簇少一个硫原子，它的生物合成可能需要[Fe4S4]核心的脱硫。我们利用Fe {NACHTUNGTRENNUNG (SiMe3) 2} 2、S8和2,4,6 -三异丙基苯硫醇（HSTip）的自组装反应，合成了p -簇[Fe8S7]核[Fe4S3 {NACHTUNGTRENNUNG (SiMe3) 2}{SCACHTUNGTRENNUNG (NMe2) 2}] 2ACHTUNGTRENNUNG (μ6-S) ACHTUNGTRENNUNG {μ-NACHTUNGTRENNUNG (SiMe3) 2} 2 (A)本文报道了在PR3 （R= Me, Et）存在下，[Fe4S4 {NACHTUNGTRENNUNG (SiMe3) 2} 4](1)[9, 10]的两个全铁[Fe4S4]团簇可以还原融合形成[Fe8S7]团簇，[Fe4S3 {NACHTUNGTRENNUNG (SiMe3) 2} ACHTUNGTRENNUNG (SPR3)] 2ACHTUNGTRENNUNG (μ6-S) ACHTUNGTRENNUNG {μ-NACHTUNGTRENNUNG (SiMe3) 2} 2 （2a， R= Et; 2b， R= Me）。由于立方体[Fe4S4]核是坚固的，启动聚变过程的关键是从[Fe4S4]核中去除硫原子。这种脱硫的一个例子是NO结合簇[Fe4S4 (NO) 4]与PEt3反应，生成[Fe4S3 (NO) 4ACHTUNGTRENNUNG (PEt3) 3]和SPEt3.[4]全铁[Fe4S4]团簇1的氧化态比更常见的[Fe4S4X4] 2À （X=硫化物，卤化物）团簇的2FeII2FeIII氧化态高两个单位，更适合于脱硫过程，将硫离子转化为SPR3硫原子，留下2eÀ。已知1的全铁[Fe4S4]核在适当的还原剂处理下可以很容易地被一个或两个电子还原。[10,11] 1与PEt3在室温下在甲苯中反应得到黑色溶液，从中分离出[Fe8S7]簇[Fe4S3 {NACHTUNGTRENNUNG (SiMe3) 2} ACHTUNGTRENNUNG (SPEt3)] 2ACHTUNGTRENNUNG (μ6-S) ACHTUNGTRENNUNG {μ-NACHTUNGTRENNUNG (SiMe3) 2} 2 (2a)，产率为29%（方案1）。analo -
Iron–sulfur clusters are ubiquitous in electron-transfer proteins,[1] and the cuboidal [Fe4S4] core is thermodynamically robust, exhibiting multiple oxidation states with only minor geometry change. Although the removal of an iron or sulfur atom from an [Fe4S4] core is chemically difficult,[2–4] the reversible transformation between [Fe4S4] and [Fe3S4] clusters has been suggested to occur under physiological conditions.[5] Further, the nitrogenase P-cluster core [Fe8S7](Figure 1),[6] which plays an important role in the electrontransfer sequence for the reduction of atmospheric dinitrogen to ammonia, has been suggested to assemble by fusion of two [Fe4S4] clusters.[7] Since the P-cluster core has one less sulfur atom than two [Fe4S4] clusters, its biosynthesis may require desulfurization of an [Fe4S4] core. We have previously synthesized the P-cluster [Fe8S7] core,[Fe4S3 {NACHTUNGTRENNUNG (SiMe3) 2}{SCACHTUNGTRENNUNG (NMe2) 2}] 2ACHTUNGTRENNUNG (μ6-S) ACHTUNGTRENNUNG {μ-NACHTUNGTRENNUNG (SiMe3) 2} 2 (A), by a selfassembly reaction of Fe {NACHTUNGTRENNUNG (SiMe3) 2} 2, SCACHTUNGTRENNUNG (NMe2) 2, S8, and 2, 4, 6-triisopropylbenzenethiol (HSTip).[8] Herein we report that in the presence of PR3 (R= Me, Et), two of the allferric [Fe4S4] clusters of [Fe4S4 {NACHTUNGTRENNUNG (SiMe3) 2} 4](1)[9, 10] can be reductively fused to form the [Fe8S7] cluster,[Fe4S3 {NACHTUNGTRENNUNG (SiMe3) 2} ACHTUNGTRENNUNG (SPR3)] 2ACHTUNGTRENNUNG (μ6-S) ACHTUNGTRENNUNG {μ-NACHTUNGTRENNUNG (SiMe3) 2} 2 (2a, R= Et; 2b, R= Me).As the cuboidal [Fe4S4] core is robust, a key to initiate the fusion process is the removal of a sulfur atom from the [Fe4S4] core. An example for such desulfurization is the reaction of the NO-bound cluster [Fe4S4 (NO) 4] with PEt3, which results in the formation of [Fe4S3 (NO) 4ACHTUNGTRENNUNG (PEt3) 3] and SPEt3.[4] The all-ferric [Fe4S4] cluster 1, with an oxidation state two units higher than the 2FeII2FeIII oxidation state of the more common [Fe4S4X4] 2À (X= thiolate, halide) clusters, would be better suited for the desulfurization process, which converts a sulfide ion into an SPR3 sulfur atom leaving 2eÀ behind. It is known that the all-ferric [Fe4S4] core of 1 can be readily reduced by one or two electrons upon treatment with appropriate reductants.[10, 11] The reaction of 1 with PEt3 in toluene at room temperature gave a black solution, from which the [Fe8S7] cluster [Fe4S3 {NACHTUNGTRENNUNG (SiMe3) 2} ACHTUNGTRENNUNG (SPEt3)] 2ACHTUNGTRENNUNG (μ6-S) ACHTUNGTRENNUNG {μ-NACHTUNGTRENNUNG (SiMe3) 2} 2 (2a) was isolated as black crystals in 29% yield (Scheme 1). An analo-