Aza- and oxadithiolates are probable proton relays in functional models for the [FeFe]-hydrogenases.
Aza- and oxadithiolates are probable proton relays in functional models for the [FeFe]-hydrogenases.
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DOI：
10.1021/ja8057666
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发表时间：
2008-12-17
影响因子：
15
通讯作者：
Rauchfuss, Thomas B.
中科院分区：
文献类型：
--
作者：
Barton, Bryan E.;Olsen, Matthew T.;Rauchfuss, Thomas B.
[FeFe]-氢化酶模型的二硫醇辅因子Fe 2（xdt）（CO）2（dppv）2（其中xdt = 1，3-丙二硫醇（pdt）、氮杂二硫醇（adt）、（SCH 2）2NH和恶二硫醇（odt）、（SCH 2）2 O; dppv = cis-1，2-bis-（diphenylphosphino）ethylene）已被探测到它们作为质子中继的功能，从而使末端二硫醇的形成和去质子化成为可能。与丙二硫醇盐衍生物相比，氮杂二硫醇盐和恶二硫醇盐显示出溶液与一个Fe中心上的末端位点之间的质子转移速率增强。结果与二硫醇盐的杂原子对于质子化和去质子化都起门控作用一致。瞬时形成的铵（pK CD 2Cl 2 5.7-8.2）或氧鎓（pK CD 2Cl 2 −4.7-1.6）的pKa调节质子转移。因此，只有氮杂二硫醇盐能够从弱酸产生末端氢化物。氮杂-和恶二硫醇盐表现出质子中继的优点：odt衍生物被证明是比pdt衍生物更快的析氢催化剂，如ic/ip对[H+]的循环伏安图所示。adt衍生物能够从弱酸[HPMe 2 Ph] BF 4（pK CD 2Cl 2 = 5.7）中进行质子还原。质子中继功能不适用于异构体桥连-[Fe 2（xdt）（μ-H）（CO）2（dppv）2]+，其中氢化物太远且太碱性而不能相互作用而不受杂原子中继位点的影响。这些μ-H物种都不能被去质子化。
The dithiolate cofactor for the [FeFe]-hydrogenase models, Fe2(xdt)(CO)2(dppv)2 (where xdt = 1,3-propanedithiolate (pdt), azadithiolate (adt), (SCH2)2NH, and oxadithiolate (odt), (SCH2)2O; dppv = cis-1,2-bis-(diphenylphosphino)ethylene) have been probed for their functionality as proton relays enabling formation and deprotonation of terminal hydrides. Compared to the propanedithiolate derivative, the azadithiolate and oxaditiholate show enhanced rates of proton transfer between solution and the terminal site on one Fe center. The results are consistent with the heteroatom of the dithiolate serving a gating role for both protonation and deprotonation. The pKa of the transiently formed ammonium (pK CD2Cl2 5.7–8.2) or oxonium (pK CD2Cl2 −4.7–1.6) regulates the proton transfer. As consequence, only the azadithiolate is capable of yielding the terminal hydride from weak acids. The aza- and oxadithiolates manifested the advantages of proton relays: the odt derivative proved to be a faster catalyst for hydrogen evolution than the pdt derivative as indicated from cyclic voltammetry plots of ic/ip vs. [H+]. The adt derivative was capable of proton reduction from the weak acid [HPMe2Ph]BF4 (pK CD2Cl2 = 5.7). The proton relay function does not apply to the isomeric bridged-hydrides [Fe2(xdt)(μ-H)(CO)2(dppv)2]+, where the hydride is too distant and too basic to interact to be affected by the heteroatomic relay site. None of these μ-H species can be deprotonated.
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影响因子：
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作者：
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作者：
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