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1、催化剂的结构(下),寇 元 北京大学 化学与分子工程学院,Laborotary of Green Catalysis, Peking University,就催化剂的催化本质而言，似可将催化剂分为三类：分子筛催化剂，纳米催化剂，和分子配合物催化剂 络合催化剂的结构特征就在于每一个金属原子/离子都发挥相同的催化效力 注意：三者各有神奇之处,6. 络合催化剂,Laborotary of Green Catalysis, Peking University,Wilkinson开创了络合催化的新时代。 Wilkinson的贡献不仅在于建立了高效的均相催化体系，发现了络合催化剂设计的结构规律，Wilki
2、nson所创立的研究方法，所采用的有机膦配体等都直接影响了其后几十年的研究与工业开发。,6. 络合催化剂,Laborotary of Green Catalysis, Peking University,6.1 Wilkinson Catalyst,1965年，Wilkinson在制取RhCl3(PPh3)3时,得到了 RhCl(PPh3)3 ,后人一直称其为Wilkinson催化剂，一个烯烃加氢制烷烃的催化剂：, 14-16e规则,Laborotary of Green Catalysis, Peking University,其后，人们发现了一个优秀的氢甲酰化催化剂：,6.1 Wilkin
3、son Catalyst,Laborotary of Green Catalysis, Peking University,CH3,M :,1971,在络合催化获得蓬勃发展之初，人们就想到了以手性膦中心实现不对称催化，但进展甚微。,6.2 Asymmetric Catalysis,Laborotary of Green Catalysis, Peking University,Sedative,Teratogen,Asymmetric Catalysis,Laborotary of Green Catalysis, Peking University,Ten of the top 20 pha
4、rmaceutical products prescribed in 1994 are molecules possessing at least one chiral center, and strict enantiopurity is required in eight out of these ten molecules.,Indinavir, a protease inhibitor currently marketed by Merck and Co., Inc., as CRIXIVAN, an anti-HIV drug,Asymmetric Catalysis,Laborot
5、ary of Green Catalysis, Peking University,获得手性物质的途径,Laborotary of Green Catalysis, Peking University,“source” of chirality in products,process,product,Racemic product mixture,Chiral building blocks,Chiral catalyst,resolution,transformation,Chirality multiplication: Asymmetric catalysis,获得手性物质的途径,Lab
6、orotary of Green Catalysis, Peking University,手性选择性,常用对映体过量百分数表示 %e.e. = 100%,R S,R + S,Laborotary of Green Catalysis, Peking University,Kagan的贡献,1970年代，Kagan创造性地提出： A: 双齿螯合膦配体 B: C2对称性 C: 手性膦中心并非必须 这直接导致了手性催化在80年代成为独立的学科并迅速在工业化上取得进展。,Wolf Foundation 2019 Price,由天然酒石酸出发，1972,Laborotary of Green Cata
7、lysis, Peking University,Kagan的贡献,Laborotary of Green Catalysis, Peking University,Knowles的同期贡献,LDopa，Monsando 80年代初,Laborotary of Green Catalysis, Peking University,寻找BINAP,Laborotary of Green Catalysis, Peking University,NOYORI的贡献,Laborotary of Green Catalysis, Peking University,Sharpless环氧化似乎证明，严
8、格C2对称性的配体也不是必需的，起码对于加氢和氢甲酰化以外的反应来说。,Sharpless环氧化,Laborotary of Green Catalysis, Peking University,注：Jacobsen的工作,Laborotary of Green Catalysis, Peking University,6.3 Ziegler-Natta Catalyst,Ziegler: TiCl4-AlEt3可以催化乙烯齐聚 Natta：丙烯齐聚，会导致聚合物的特异结构 50年代中期实现了聚丙烯工业化,Laborotary of Green Catalysis, Peking Univer
9、sity,6.3 Ziegler-Natta Catalyst,Laborotary of Green Catalysis, Peking University,6.3 Ziegler-Natta Catalyst,Laborotary of Green Catalysis, Peking University,Ziegler-Natta Catalyst,Laborotary of Green Catalysis, Peking University,Ziegler-Natta Catalyst,Laborotary of Green Catalysis, Peking University
10、,6.4 Olefin Metathesis,烯烃的双键断裂重新组成新的烯烃 早期的反应是在Ziegler-Natta催化剂上实现的,Laborotary of Green Catalysis, Peking University,6.4 Olefin Metathesis,由降冰片烯制合成橡胶,Laborotary of Green Catalysis, Peking University,6.4 Olefin Metathesis,Macromol. Chem. 141(1970)161,其后，各种金属中心（V, Ta, Mo, W, Ru, Os)被广泛试探过(R H Schrock),
11、Laborotary of Green Catalysis, Peking University,6.4 Olefin Metathesis,Laborotary of Green Catalysis, Peking University,Olefin Metathesis,最成功的是Grubbs的Ru卡宾络合物系列,JACS, 119(2019)3891,Laborotary of Green Catalysis, Peking University,6.5 络合催化剂概论,络合催化剂的金属中心一般是单核的, 少部分有双核的, 没有多核的. 值得注意的是, 尽管双核异核络合物并不少见, 但用
12、作催化剂却不见报道, 这与担载催化剂相比有明显差别. 络合催化剂金属中心的三维立体-多位络合决定了络合催化剂不仅会有chemo-和stereo-selectivity, 而且会有enantio-selectivity, 因此络合催化体系专一性高, 是高选择性催化体系. 络合催化剂的主要缺点是分离繁琐, 不易为工业采用. 改进的办法: 1. 两相化 (bi-phase); 2. 固相化(immobilization);,Laborotary of Green Catalysis, Peking University,两相化原理,Laborotary of Green Catalysis, Peking University,水溶性膦配体:,Laborotary of Green Catalysis, Peking University,水溶性氮配体,Science 287, 1636, 2000,水溶性配体的昂贵价格制约了其应用,Laborotary of Green Catalysis, Peking University,固相化示意,Laborotary of Green Catalysis, Peking University,固相化使金属中心部分地失去了其三维自由旋转的结构特征, 导致的活性下降是必然的. 这可能是这种方法不可克服的局限性.,固相化示意,
