N-heterocyclic carbene ligands in nonsymmetric diiron models of hydrogenase active sites
N-heterocyclic carbene ligands in nonsymmetric diiron models of hydrogenase active sites
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DOI：
10.1021/om061173l
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发表时间：
2007-04-09
期刊：
影响因子：
2.8
通讯作者：
Kervarec, Nelly
中科院分区：
文献类型：
--
作者：
Morvan, Didier;Capon, Jean-Francois;Kervarec, Nelly
[Fe-2{mu-S(CH2)(3)S}(CO)(6)](1)在室温下与n -杂环碳烯I-Me-(CH2)(2)-L （I-Me = 1-甲基咪唑-2-基烯，L = NMe2, SMe）反应得到五羰基碳烯衍生物[Fe-2{mu-S(CH2)(3)S}(CO)(5){I-Me-(CH2)(2)-NMe2}] （2a）和[Fe-2{mu-S(CH2)(3)S}(CO)(5){I-Me-(CH2)(2)-SMe}] （2b）。1与I-Me-CH2-I-Me在室温下反应得到二聚体[{Fe-2(mu-S(CH2)(3)S)(CO)(5)}(2){mu-(I-Me-CH2-I-Me)}](3)和螯合的双nhc配合物[Fe-2{mu-S(CH2)(3)S}(CO)(4){I-Me-CH2-I-Me}] （4a）为主要产物。1与I-Me-(CH2)(2)-I-Me的类似反应生成了螯合的双nhc配合物[Fe-2(mu-S(CH2)(3)S)(CO)(4){I-Me-(CH2)(2)-I-Me}] （4b）。在化合物4a中加入HBF4，可与NHC配体形成稳定的桥接氢化物配合物[Fe-2(mu-H){mu-S(CH2)(3)S}(CO)(4){I-Me-CH2-I-Me}](BF4) (5a, b)，分别在5a， b中以基/基和基/尖配位模式进行配位。通过x射线衍射研究证实了2a、3、4a、b和5a的分子结构。对4a质子化的低温核磁共振研究显示了非常不稳定的末端氢化物和通过C-4(5)键与NHC配体具有非经典配位模式的桥接氢化物的形成的光谱证据。循环伏安法表明，4a是一种质子还原催化剂。
Reaction of [Fe-2{mu-S(CH2)(3)S}(CO)(6)] (1) at room temperature with the N-heterocyclic carbenes I-Me-(CH2)(2)-L (I-Me = 1-methylimidazol-2-ylidene, L = NMe2, SMe) afforded the pentacarbonyl carbene derivatives [Fe-2{mu-S(CH2)(3)S}(CO)(5){I-Me-(CH2)(2)-NMe2}] (2a) and [Fe-2{mu-S(CH2)(3)S}(CO)(5){I-Me-(CH2)(2)-SMe}] (2b). Reaction of 1 with I-Me-CH2-I-Me at room temperature provided the dimer [{Fe-2(mu-S(CH2)(3)S)(CO)(5)}(2){mu-(I-Me-CH2-I-Me)}] (3) together with the chelated bis-NHC complex [Fe-2{mu-S(CH2)(3)S}(CO)(4){I-Me-CH2-I-Me}] (4a) as the major product. The analogous reaction of 1 with I-Me-(CH2)(2)-I-Me yielded the chelated bis-NHC complex [Fe-2(mu-S(CH2)(3)S)(CO)(4){I-Me-(CH2)(2)-I-Me}] (4b). Addition of HBF4 to compound 4a afforded the stable bridging hydride complexes [Fe-2(mu-H){mu-S(CH2)(3)S}(CO)(4){I-Me-CH2-I-Me}](BF4) (5a, b) with NHC ligands in a basal/basal and basal/apical mode of coordination in 5a, b, respectively. The molecular structures of 2a, 3, 4a, b, and 5a were confirmed by X-ray diffraction studies. Low-temperature NMR studies on the protonation of 4a showed spectroscopic evidence for the formation of a very unstable terminal hydride and a bridging hydride species with a NHC ligand having a non classical mode of coordination via a C-4(5) bond. Cyclic voltammetry revealed that 4a is a catalyst for proton reduction.