Biomimetic hydrogen evolution catalyzed by an iron carbonyl thiolate
Biomimetic hydrogen evolution catalyzed by an iron carbonyl thiolate
复制标题
DOI：
10.1021/ja016516f
复制
发表时间：
2001-09-26
影响因子：
15
通讯作者：
Rauchfuss, TB
中科院分区：
文献类型：
--
作者：
Gloaguen, F;Lawrence, JD;Rauchfuss, TB
用于质子还原的均相催化剂引起了人们的兴趣，因为它们易于系统操作，并且它们代表了定制的非均相催化剂的可行前体，包括那些使用更具经济吸引力的贱金属（如铁）的催化剂。氢化酶是一种结构不寻常但高效的氢处理催化剂，它依赖于贱金属（Ni, Fe）。2氢化酶的两个主要家族，Fe-only和NiFe氢化酶的结构，在高分辨率上是已知的。3的活性部位Fe-only铁氢化酶由一个(μSR) 2 (CN) 2 (CO) 3 ln核心(L) H2O / H2和thiolate-linked Fe4S4 (SR) 4集群,方案1)。4这个核心关键结构特点与有机金属配合物的铁(μSR) 2 (CO) 6,自1920年代以来已经知道。5所以稳定价(μSR) 2 (CO) 6衍生品这类化合物形式在严酷的条件下(例如,50 - 200 MPa在250 C)从原始的试剂(菲斯,RSH, HCO2H)。我们已经报道了模型配合物{Fe2 [μ-S2 (CH2) 3](CN) 2-(CO) 4} 2-（1，方案1）与质子反应生成亚化学计量量的二氢。不幸的是，酸也会将1（和相关的碘离子）转化为不溶性和催化活性的未知结构的聚合物衍生物。1不适合作为催化剂是由于它的高度还原特性，由前面提到的直接还原质子的能力以及电化学测量支持。这个逻辑使我们研究了络合物{Fe2 [μ-S2 (CH2) 3](CN)(CO) 4 (PMe3)}-(2)，它的还原性小于1。如下所述，2是质子还原的活性催化剂，因此在有机金属模型和纯铁氢化酶之间提供了第一个功能联系。在评价催化作用时，我们首先考察了2的质子化。在加入过量H2SO4的MeCN溶液中，以分析纯度析出深红色的HFe2 [μ-S2 (CH2) 3](CN)(CO) 4 (PMe4)(3)（见方案2）。该物质的1H NMR谱在δ)-17 (JH-P) 23 Hz处显示一个31p耦合的双重态信号，与Fe-Fe键的质子化相一致。胺基不能把3变成2，可能反映了
Homogeneous catalysts for proton reduction1 are of interest because they are amenable to systematic manipulation, and they represent viable precursors to tailored heterogeneous catalysts, including those using more economically attractive base metals such as Fe. Hydrogenase enzymes represent a structurally unusual but highly efficient hydrogen-processing catalysts that rely on base metals (Ni, Fe). 2 The structures of both major families of hydrogenase enzymes, the Fe-only and the NiFe hydrogenases, are known at high resolution. 3 The active site of the Fe-only hydrogenases consists of an Fe2 (μ-SR) 2 (CN) 2 (CO) 3Ln core (L) H2O/H2 and a thiolate-linked Fe4S4 (SR) 4 cluster, Scheme 1). 4 This core shares key structural features with organometallic complexes Fe2 (μ-SR) 2 (CO) 6 that have been known since the 1920s. 5 So stable are the Fe2 (μ-SR) 2 (CO) 6 derivatives that such compounds form under harsh conditions (eg, 50-200 MPa at 250 C) from primitive reagents (FeS, RSH, HCO2H). 6 We have reported that model complex {Fe2 [μ-S2 (CH2) 3](CN) 2-(CO) 4} 2-(1, Scheme 1) reacts with protons to give substoichiometric amounts of dihydrogen. 7 Unfortunately acid also converts 1 (and related dianions) into insoluble and catalytically inactive polymeric derivatives of unknown structure. The unsuitability of 1 as a catalyst is attributable to its highly reducing character, supported by the aforementioned ability to reduce protons directly as well as by electrochemical measurements. 8 This logic led us to investigate the complex {Fe2 [μ-S2 (CH2) 3](CN)(CO) 4 (PMe3)}-(2) which is less reducing than 1. As described below, 2 is an active catalyst for proton reduction, and as such provides the first functional link between organometallic models and the Fe-only hydrogenases.In evaluating the catalysis, we first examined the protonation of 2. Dark red HFe2 [μ-S2 (CH2) 3](CN)(CO) 4 (PMe4)(3) precipitates in analytical purity from MeCN solutions of 2 upon addition of excess aqueous H2SO4 (see Scheme 2). The 1H NMR spectrum of this species shows a 31P-coupled doublet signal at δ)-17 (JH-P) 23 Hz), consistent with protonation of the Fe-Fe bond. Amine bases do not convert 3 into 2, probably reflecting the