[Fe2(SR)2(μ-CO)(CNMe)6]2+ and analogues:: A new class of diiron dithiolates as structural models for the HoxAir air state of the Fe-only hydrogenase
[Fe2(SR)2(μ-CO)(CNMe)6]2+ and analogues:: A new class of diiron dithiolates as structural models for the HoxAir air state of the Fe-only hydrogenase
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DOI：
10.1021/ja049050k
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发表时间：
2004-11-24
影响因子：
15
通讯作者：
Bénard, M
中科院分区：
文献类型：
--
作者：
Boyke, CA;Rauchfuss, TB;Bénard, M
Fe-2（S_2CnH_2n）（CNMe）（6-x）（CO）（x）（n = 2，3; x = 2，3）的低温氧化得到一族[Fe-2（S_2CnH_2n）（CO）（x）CNMe）（7-2）]（2+）型混合羰基异腈。取代度由RNC/Fe比以及铁的初始取代度控制，其中三羰基衍生物有利于更高度羰基化的产物。单羰基衍生物[Fe-2（S_2CnH_2n）-（μ-CO）（CNMe）（6）]（PF_6）（2）（n = 2，3）的晶体学和光谱学结构非常相似，Fe-Fe距离约为2.5埃，尽管μ-CO在丙二硫醇衍生物中是不对称的。[Fe-2（S2 C3 H6）（CO）（CNMe）（6）]（PF 6）（2）的异构体形式被表征，其中CO是桥接的或末端的，最大的结构差异是当MeNC（相对于CO）是桥接的时，Fe-Fe距离的0.1埃伸长。在二羰基化合物[Fe-2（S2 C2 H4）（mu-CO）（CO）（CNMe）（5）]（PF 6）（2）中，末端CO配体位于其中一个碱基位点，而不是反式的Fe-Fe载体。Fe-2（S2 C2 H4）（CNMe）（3）（CO）（3）在1 atm CO下氧化得到深粉红色三羰基[Fe-2（S2 C2 H4）（CO）（3）（CNMe）（4）]（PF 6）（2）。DFT计算表明，一个桥接CO或MeNC建立一个3-中心，2-电子键内的两个Fe（II）中心，否则将是非键合。
Low-temperature oxidation of Fe-2(S2CnH2n)(CNMe)(6-x)(CO)(x) (n = 2, 3; x = 2, 3) affords a family of mixed carbonyl-isocyanides of the type [Fe-2(S2CnH2n)(CO)(x)CNMe)(7-2)](2+). The degree of substitution is controlled by the RNC/Fe ratio, as well as the degree of initial substitution at iron, with tricarbonyl derivatives favoring more highly carbonylated products. The structures of the monocarbonyl derivatives [Fe-2(S2CnH2n)-(mu-CO)(CNMe)(6)](PF6)(2) (n = 2,3) established crystallographically and spectroscopically, are quite similar, with Fe---Fe distances of ca.2.5 Angstrom, although the mu-CO is unsymmetrical in the propanedithiolate derivative. Isomeric forms of [Fe-2(S2C3H6)(CO)(CNMe)(6)](PF6)(2) were characterized where the CO is bridging or terminal, the greatest structural difference being the 0.1 Angstrom elongation of the Fe---Fe distance when MeNC (vs CO) is bridging. In the dicarbonyl species, [Fe-2(S2C2H4)(mu-CO)(CO)(CNMe)(5)](PF6)(2), the terminal CO ligand is situated at one of the basal sites, not trans to the Fe---Fe vector. Oxidation of Fe-2(S2C2H4)(CNMe)(3)(CO)(3) under 1 atm CO gives the deep pink tricarbonyl [Fe-2(S2C2H4)(CO)(3)(CNMe)(4)](PF6)(2). DFT calculations show that a bridging CO or MeNC establishes a 3-center, 2-electron bond within the two Fe(II) centers, which would otherwise be nonbonding.