【作者】 李彬；

【导师】 冯亚青； Marcetta Y.Darensbourg；

【作者基本信息】 天津大学 ， 应用化学， 2010， 博士

【摘要】 氢化酶仿生化学是当前生物有机金属化学研究领域的前沿课题,其核心内容是活性中心的结构和功能模拟研究。本论文研究了双铁氢化酶以及单铁氢化酶活性中心模型化合物的合成,表征,反应性以及相关的理论探索。对模型配合物（μ-pdt）[Fe₂（CO）₃]₂及其有机膦配体取代衍生物进行了氧化研究,合成了用于模拟双铁氢化酶活性中心氧气敏感性的模型化合物,并利用1H NMR、31P NMR、IR和MS,EA对所合成的新化合物进行了结构表征,通过X-射线单晶分析,测定了其中五个配合物的晶体结构。DFT理论计算发现基于Fe-Fe键的氧化产物是热力学稳定产物,而氧化实验分离得到了基于硫原子氧化的动力学控制产物。通过化学还原以及电化学还原方法对相应的氧化模型配合物进行了脱氧研究,讨论了氧化与脱氧与氢化酶氧气敏感性的潜在联系。通过对模型配合物（μ-pdt）[Fe₂（CO）₃]₂（1）及其氧化产物（μ-pst）[Fe₂（CO）₃]₂（1-O）的羰基/膦配体取代反应动力学研究,考察了基于硫原子的氧化对配体取代反应能垒的影响。发现该反应能垒包括两部分:分子内结构重排的能垒和取代配体亲核进攻的能垒。配合物1的两步CO/PMe₃取代反应均遵循协同作用机理;其中,第二步取代反应能垒大于第一步反应,是速率控制步骤。配合物1-O与PMe₃反应较慢,动力学研究在较高温度下进行,发现第一步取代反应为协同作用机理与解离作用机理并行。配合物1-O中CO/CN-取代反应动力学研究发现,两步取代反应均为协同作用机理,并且配合物1-O的取代反应能垒大于配合物1中CO/CN-取代反应能垒。理论计算与相应的变温核磁研究考察了配合物中Fe（CO）₃中心翻转能垒的变化;研究发现,由于基于硫原子的氧化影响,配合物1-O中Fe（CO）₃中心翻转能垒较大。通过前体配合物FeI₂（CO）₄与相应氮杂环卡宾配体、有机膦配体和二齿氮配体的取代反应,合成了一系列分子式为FeI₂（CO）_xL_4-x,（x=2或3）的单铁氢化酶活性中心前体模型配合物。并利用¹H NMR、³¹P NMR、IR和MS,EA对所合成的新化合物进行了结构表征,通过X-射线单晶分析,测定其中六个配合物的晶体结构。通过红外吸收光谱和穆斯保尔谱（Mossbauer）,研究了所合成模型化合物与单铁氢化酶活性中心的相关联系。通过该系列模型化合物与氮硫二齿配体的取代反应,合成了五个性能更好的模型配合物,通过X-射线单晶分析,测定其中三个配合物的晶体结构,并研究了其相关反应性。更多还原

【Abstract】 Hydrogenase active site bio-mimetic chemistry is one of the important and hot area in bio-organometallic chemistry. This dissertation describes synthesis, characterization, reactivities and theoretical investigations of binuclear or mononuclear Fe carbonyl complexes that model the active site of the [FeFe]- and [Fe]-H2ases.Sulfur oxygenation of （μ-pdt）[Fe₂（CO）₃]₂ and its phosphine derivatives provides synthetic model complexes relevant to the oxygen sensitivity of the [FeFe]-H2ase. All the new synthesized complexes are characterized by 1H NMR、31P NMR、IR、MS and EA. Five of them has been determined by X-ray diffraction measurement. DFT computations find the Fe-Fe bond in the FeIFeI diiron models is thermodynamically favored to produce oxidative addition product, nevertheless the sulfur-based oxidized products are isolated as the kinetic products by synthesis experiment. Deoxygenation of theμ-pst complexes are conducted by chemical reduction and electrochemical reduction method. The possible biological relevance of oxygenation and deoxygenation studies is discussed.Kinetic studies of CO/L substitution reactions of the well-known organometallic complex （μ-pdt）[Fe（CO）₃]2, complex 1, and its sulfur-oxygenated derivative （μ-pst）[Fe（CO）₃]2, 1-O, have been carried out with the goal of understanding the influence of the sulfenato ligand on the activation barrier to ligand substitution in such diiron carbonyl complexes which consists of two components: intramolecular structural rearrangement （or fluxionality） and nucleophilic attack by the incoming ligand. The CO/PMe3 substitution reactions of complex 1 follow associative mechanisms in both the first and second substitutions; the second substitution is found to have a higher activation barrier for the overall reaction that yields 1-（PMe₃）₂. Complex 1-O reacts more sluggishly with PMe₃, where practical kinetic measurements are at such high temperatures that CO dissociation parallels the associative path. Kinetic studies have established that in complex 1-O both the first and second CO/CN- substitutions proceed via associative paths with higher Eact barriers than the analogous reactions with complex 1. Theoretical calculations （DFT） have been used in conjunction with variable temperature ¹³C NMR spectral studies to examine the energy barriers associated with rotation of the Fe（CO）₃ unit. The activation energy required for rotation is higher in the sulfenato than in the analogous thiolato complexes.A series of mono- and di-substituted complexes, FeI₂（CO）_xL_4-x, x = 2 or 3, is conveniently accessed from simple mixing of N-heterocyclic carbenes, phosphines and aromatic amines with FeI₂（CO）₄. All the new complexes are characterized by 1H NMR、³¹P NMR、IR、MS and EA. Six of them has been determined by X-ray diffraction measurement. Diatomic ligand （ν（CO）） vibrational and Mossbauer spectroscopies are related to those reported for the Hmd active site. Interesting results on structures and reactivities of better [Fe]-H2ases active site complexes, （NS）Fe（CO）₂P will also be discussed.更多还原