【作者】 冀汝南；

【导师】 刘双喜；

【作者基本信息】 南开大学 ， 物理化学， 2013， 博士

【摘要】 Salen是一种常见的多齿配体,它的两个N,两个O原子处于同一平面内,可以与多种金属形成配合物,由于中心金属原子在垂直于salen配体平面的轴向存在空轨道,可以十分方便地与其他物质配位,所以金属salen配合物在催化领域有着广泛的应用。随着近些年手性化合物需求量的迅速增长,手性Mn(Ⅲ)salen配合物开始被用于手性催化领域,而且由于其高的反应活性和对映选择性,它成为了最重要的手性催化剂之一。然而由于均相的手性Mn(Ⅲ) salen催化剂不易于产物分离,不易回收。所以,近十年来,对于非均相手性Mn(Ⅲ) salen催化剂的研究成为催化界的热点,它可以用于催化烯烃的不对称环氧化、外消旋二级醇的氧化动力学拆分和硫醚的不对称氧化等反应。首先,本文考察了载体孔径精细调变对于不对称结构的Mn(Ⅲ) salen非均相催化剂的催化性能的影响,将不对称结构的Mn(Ⅲ) salen配合物固载到一系列孔径精细调变的MCM-41和MCM-48上,采用红外光谱、固体紫外光谱、N2吸附脱附、X-射线衍射等手段对催化剂进行了表征,表明催化剂被成功固载且载体结构未发生变化。通过烯烃不对称环氧化反应,考察了3-巯丙基三甲氧基硅烷对催化剂性能的影响,并确定了最佳用量。在此基础上,本文研究了孔径的精细调变对于催化剂性能的影响,发现固载到孔径较大的介孔材料上的Mn(Ⅲ) salen非均相催化剂获得了较高的催化活性和对映选择性。其次,本文考察了不对称结构的Mn(Ⅲ) salen均相和非均相催化剂在不同氧化体系下的催化性能,将不对称结构的Mn(Ⅲ) salen配合物固载到MCM-41、MCM-48和SBA-15上,通过各种表征证明了活性组分固载到了载体上,且载体原有结构得到了很好的保持。n-CPBA和NaCIO丙种氧化剂用于烯烃的不对称环氧化反应,当使用非均相Mn(Ⅲ) salen催化剂时,两种氧化剂在反应中获得的底物转化率有显著的差异,而在使用均相Mn(Ⅲ) salen催化剂时,两种氧化剂获得的转化率基本一致,换句话说,Mn(Ⅲ) salen配合物的非均相化对于m-CPBA和NaClO有不同的影响。为了研究这一现象,文中采用紫外-可见光谱及反应动力学研究了两个反应体系,发现由于NaClO是一种温和的氧化剂,在反应过程中无明显的催化剂中间体[salen-Mn(V)=O]+累积失活的现象,这是NaClO在非均相条件下取得较好的转化率的原因。此外,与以MCM-41为载体的非均相Mn(Ⅲ) salen催化剂相比,固载到MCM-48和SBA-15上的非均相催化剂获得了较好的催化活性和对映选择性,这与MCM-48拥有三维孔道结构及SBA-15拥有大的孔径有利于底物分子扩散有关。再次,本文采用废轮胎热解炭黑作为载体,不加入任何有机硅烷,没有采用氧化方式改变炭黑表面含氧基团的数量,十分经济的将手性Mn(Ⅲ) salen配合物直接共价固载到了炭黑表面,制备的非均相Mn(Ⅲ) salen催化剂在烯烃不对称环氧化反应中取得了很好的催化结果,特别是在1-苯基环己烯的不对称环氧化反应中,获得了高于均相催化剂的ee值。此外,该类非均相催化剂可以循环使用三次。最后,本文分别利用1,2-乙硫醇、1,3-丙二硫醇和1,6-己二硫醇与Mn(Ⅲ)salen配合物构建了一系列环状硫醚手性Mn(Ⅲ) salen配合物。通过核磁共振、质谱和红外光谱表明环状硫醚结构的成功合成。该类催化剂在反应体系中保持了很高的催化活性,在加入正己烷的情况下,极容易从反应体系中分离出来。本文确定了最佳的反应体系,即NaCIO与PPNO的氧化体系,采用的最佳溶剂为二氯甲烷。在烯烃的不对称环氧化反应中,取得了与环状硫醚手性Mn(Ⅲ)salen配合物结构相似的Mn(Ⅲ) salen配合物可比的催化性能,而且该类催化剂可以循环使用六次。更多还原

【Abstract】 Salen is a common chelating ligand, in which two N atoms and O atoms were on the same plane, and it can coordinate with many kinds of transit metal. As a result of the existence of unoccupied orbital in metal salen complexes axially, which can coordinate with many functionalized groups, metal salen complexes are widely applied in catalysis field. With the increased demand of chiral compounds, enantioselective metal salen complexes are used in chiral catalysis area, and because of their high activity and enatioselectivity, they have become privileged chiral catalysts. Among metal salen complexes, Mn(Ⅲ) salen complex proves to be an important complex, which can catalyzed many reactions, such asymmetric epoxidation of olefins, oxidation kinetics resolution of racemic secondary alcohols and asymmetric oxidation of sulfide. However, due to the difficulty in product separation and catalyst recycling for homogeneous Mn(Ⅲ) salen complex, heterogeneous Mn(Ⅲ) salen catalysts have attracted much attention in last decade.First, it was investigated that the effect of fine tuning pore size for the catalytic performance of unsymmetric Mn(Ⅲ) salen heterogeneous catalysts, and an unsymmetric Mn(Ⅲ) salen complex was immobilized on a series of MCM-41and MCM-48with fine-tuning pore size. These heterogeneous catalysts were characterized by FT-IR, DR UV-vis, N2sorption and XRD, and these characterizations indicated that the active specie was grafted successfully and the structures of supports were kept well. The dosage of3-Mercaptopropyltrimethoxysilane was studied in epoxidation of olefins, which could influence the catalytic performance of heterogeneous catalysts. The optimum organosilane was determined, and on the basis of this, the effect of fine-tuning pore size for catalytic performance of catalysts was investigated. It was found that the heterogeneous catalysts immobilized on mesoporous silica with larger pore size showed higher catalytic activity and enantioselectivity.Second, it was studied that the comparison of catalytic performace of homogeneous and heterogeneous Mn(Ⅲ) salen catalysts using different oxidants, and two kinds of unsymmetric Mn(Ⅲ) salen complexes were grafted on mesoporous silica MCM-41, MCM-48and SBA-15. Several characterizations were employed and they indicated that Mn(Ⅲ) salen complexes were immobilized on the support successfully and the mesoporous structures of supports were retained very well. Two oxidants, m-CPBA and NaCIO, were applied in asymmetric epoxidation of unfunctionalized olefins. As the heterogeneous catalysts Mn(Ⅲ) salen catalysts were chosen, the conversions obtained by two oxidants showed remarkable different (NaCIO obtained great higher conversions), while the conversions obtained by two oxidants presented no obvious difference using homogeneous catalysts. In other words, the heterogenization of Mn(Ⅲ) salen complexes gave different influence for two oxidation system of m-CPBA and NaCIO. In order to research this phenomenon, UV-vis spectra and reaction kinetics were employed to study two oxidation system mentioned above, and it was found that as a result of the mildness of NaClO, no obvious accumulation of intermediate [Mn(Ⅴ)=O salen]+was observed. This was the reason that NaClO gave higher conversions in heterogeneous condition. In addition, compared with the heterogeneous catalysts immobilized MCM-41, the heterogeneous catalysts immobilized on MCM-48and SBA-15showed better catalytic activity and enantioselectivity, and this was due to3D pore structure of MCM-48and larger pore size of SBA-15, which improved molecular diffusion.Third, in this paper, pyrolytic waste tire char (PWTC) was chosen as support, and without any organosilane and oxidation process, Mn(Ⅲ) salen complexes were immobilized on PWTC directly. The prepared heterogeneous Mn(Ⅲ) salen catalysts obtained good catalytic results in asymmetric epoxidation of olefins, and especially in the epoxidation of1-phenylcyclohexene, they obtained higher ee values than their homogeneous counterparts. Moreover, the heterogeneous catalyst could be recycled three times.Fourth, with the employment of1,2-ethanedithiol,1,3-propanedithiol and1,6-hexanedithiol, a series of cyclic sulfide Mn(Ⅲ) salen complexes were synthesized. Though the characterizations of NMR, MS and FT-IR, it was confirmed that the cyclic sulfide structure was synthesized successfully. In asymmetric epoxidation of olefins, the oxidation system of NaClO/PPNO was chosen, and dichloromethane was employed as solvent. These cyclic sulfide Mn(Ⅲ) salen complexes presented good catalytic performance in asymmetric epoxidation of unfunctionalized olefins. With the addition of hexane, these Mn(Ⅲ) salen complexes were separated easily and they could be recycled six times.更多还原