Mixed-valence [FeIFeII] hydrogenase active site model complexes stabilized by a bidentate carborane bis-phosphine ligand
Mixed-valence [FeIFeII] hydrogenase active site model complexes stabilized by a bidentate carborane bis-phosphine ligand
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DOI：
10.1039/c2dt31192e
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发表时间：
2012-01-01
影响因子：
4
通讯作者：
Ott, Sascha
中科院分区：
文献类型：
--
作者：
Karnahl, Michael;Tschierlei, Stefanie;Ott, Sascha
一系列[FeFe]-氢化酶活性位点类似物，通式为[Fe-2(dt)(CO)(4)(BC)] 1-3（dt = 二硫醇盐，pdt = 丙基-1,3-dt (1)，bdt = 苯-1,2-dt (2)，edt = 乙基-1,2-dt (3)；BC = 1,2-双二苯基膦-1,2-邻碳硼烷）已被制备并进行了结构表征。虽然 1-3 的电化学还原在很大程度上不受其 dt 桥的不同性质影响，但系列之间的氧化差异超过 120 mV。值得注意的是，所有三种化合物均被可逆氧化，其中配合物 1 含有最多给电子的 pdt 配体，其电位相对于 Fc/Fc(+) 的最低电位为 -0.09 V。单电子氧化态 1(ox) 可稳定几分钟，并通过 FTIR 和 EPR 进行光谱表征。 EPR 光谱提供的证据表明，在混合价 [(FeFeII)-Fe-I] 状态下，大部分自旋密度位于具有 BC 配体的铁上。这是通过 BC 配体的苯基的强 P-31 超精细耦合来监测的，而进一步离域到邻碳硼烷单元中的情况可以忽略不计。
A series of [FeFe]-hydrogenase active site analogues, with the general formula [Fe-2(dt)(CO)(4)(BC)] 1-3 (dt = dithiolate, pdt = propyl-1,3-dt (1), bdt = benzene-1,2-dt (2), edt = ethyl-1,2-dt (3); BC = 1,2-bisdiphenylphosphine-1,2-o-carborane), has been prepared and structurally characterized. While the electrochemical reductions of 1-3 are largely invariant to the different nature of their dt bridges, the oxidations differ by more than 120 mV in between the series. Remarkably, all three compounds are reversibly oxidized, with complex 1 that contains the most electron-donating pdt ligand at the mildest potential of -0.09 V vs. Fc/Fc(+). The one-electron oxidized state 1(ox) is stable for several minutes and was spectroscopically characterized by FTIR and EPR. EPR spectroscopy provided evidence that in the mixed-valence [(FeFeII)-Fe-I] state most of the spin density is located on the iron with the BC-ligand. This is monitored through the strong P-31 hyperfine coupling of the phenyl groups of the BC ligand, while further delocalization into the o-carborane unit is negligible.