【作者】 王艳红；

【导师】 张天永；

【作者基本信息】 天津大学 ， 应用化学， 2015， 硕士

【摘要】 以（μ-dmedt）[Fe（CO）3]2（I,dmedt=2,3-丁二硫醇）为母体配合物,设计合成了一系列新的单齿、双齿氮杂环卡宾配体（NHC）取代的[Fe-Fe]氢化酶活性中心模型配合物（II,（μ-dmedt）[Fe（CO）2]2[IMe（CH₂）2IMe],IMe=1-甲基咪唑-2-亚甲基;III,{（μ-dmedt）[Fe2（CO）5]}2[IMe（CH₂）2IMe];IV,（μ-dmedt）[Fe2（CO）5]IMes,IMes=1,3-二（2,4,6-三甲基苯基）咪唑-2-亚甲基;V,（μ-dmedt）[Fe2（CO）5]IMe,IMe=1,3-二甲基咪唑-2-亚甲基;VI,（μ-dmedt）[Fe2（CO）5]IPr,IPr=1,3-二（2,6-二异丙基苯基）咪唑-2-亚甲基）。对于这六种配合物均采用红外光谱、核磁共振、元素分析和X-射线单晶衍射的方法进行结构表征。通过循环伏安法,测试了配合物I-VI的电化学性质及其在不同质子源（HOAc或H₂O）存在下电化学性质的变化。评价了配合物I-V催化苯羟基化的反应活性。并通过密度函数理论计算（DFT）,得到了配合物I、II和IV的理论优化结构及其氧化产物的吉普斯自由能。实验结果表明,配合物II具有基位/基位顺式取代的对称结构,目前为止,该构型在NHC取代的双铁配合物中首次发现。同时IPr配体也是首次应用于[2Fe2S]活性中心。配合物I-VI均具有催化质子制氢的能力,由于配合物II中的NHC具有较强的δ电子供应能力和电子定域效应,使得其还原电位电势最低。所合成的配合物对空气、水和弱酸性环境表现出较好的稳定性。同时拓展了[Fe-Fe]-NHC配合物的催化应用,将所合成的配合物I-V应用于直接催化苯羟基化制苯酚。在最优的实验条件下（即催化剂配合物II,0.01mmol;苯,0.1m L;CH3CN,2.0m L;H₂O2,6.0mmol;60°C;3h）,苯酚的收率为26.7%,并表现出较高的选择性。DFT计算结果表明,配合物I、II和IV的理论优化结构与通过X-射线单晶衍射手段所测得的晶体结构一致。羟基化反应过程中,从热力学角度和DFT计算结果来讲,基于铁铁键氧化的（FeII-（μ-O）-FeII）物种比基于S氧化的[2Fe2S（S=O）]物种的吉布斯自由能低,相对较稳定,更容易生成。更多还原

【Abstract】 A serious of novel biomimic hydrogenase complexes, diiron-hexacarbonyl-butanedithiol complex（μ-dmedt）[Fe（CO）3]2（I, dmedt = 2, 3-butanedithiol） and N-heterocyclic carbene（NHC） substituted（μ-dmedt）[Fe-Fe]-NHC（II,（μ-dmedt）[Fe（CO）2]2[IMe（CH₂）2IMe], IMe = 1-methylimidazol-2-ylidene; III, {（μ-dmedt）[Fe（CO）5]}2[IMe（CH₂）2IMe]; IV,（μ-dmedt）[Fe2（CO）5]IMes, IMes = 1, 3-bis（2, 4, 6-trimethylphenyl）imidazol-2-ylidene; V,（μ-dmedt）[Fe2（CO）5]IMe, IMe = 1, 3-dimethylimidazol-2-ylidene; VI,（μ-dmedt）[Fe2（CO）5]IPr, IPr = 1, 3- bis（2, 6-diisopropylphenyl） imidazol-2-ylidene） were synthesized and characterized by solution IR spectra, NMR spectra, elemental analysis and X-ray crystallography. The electrochemical properties of complexes I-VI and different proton sources（HOAc or H₂O） were investigated by cyclic voltammetry in coordinating solvent CH3 CN to evaluate the effects of different NHC ligands on the redox properties of the iron atoms of the series complexes. The catalytic reactivity for direct hydroxylation of benzene to phenol by [Fe-Fe]-NHC complexes was investigated. In addition, the optimized structures of I, II and IV, and the Gibbs free energy of their oxidation products were obtained by density functional theory calculation（DFT）.The symmetrically substituted cisoid basal/basal coordination complex II displays the lowest reduction potential own to its most δ-donating of NHC and the orientation of the NHC donor carbon as a result of the constraints of the bridging bidentate ligands. The kind of configuration of II is the first obtained in the field of [Fe-Fe]-NHC. And IPr as a ligand is first used to coordinate with [2Fe2S] active center. All the new complexes are catalysts for proton reduction to hydrogen. The redox potential is very close to the electron cloud density around Fe-Fe bond. All of the six complexes are relatively stable to air, water and weak acid.A new catalytic application for the [Fe-Fe]-NHC model complexes in the directly catalytic hydroxylation of benzene to phenol was also studied. Under the optimized experimental conditions（II, 0.01mmol; benzene, 0.1m L; CH3 CN, 2.0m L; H₂O2, 6.0mmol; 60°C, 3h）, the maximal phenol yield is 26.7%.The DFT calculation results indicated that DFT optimized structures of complexes I, II and IV are agree with the experimental results by X-ray crystallography. The Gibbs free energy of Fe-based oxygenated intermediate, FeII-（μ-O）-FeII, is lower than S-based oxygenated intermediate, [2Fe2S（S=O）]. So the former is thermodynamically favored and more stable than the latter.更多还原