【作者】 陈越；

【导师】 李晓燕；

【作者基本信息】 山东大学 ， 有机化学， 2008， 博士

【摘要】 芳香卤化物在有机合成化学中占据重要地位。由于C-Cl、C-F键键能较强，氯代、氟代芳香化合物明显的缺乏反应活性。由此，越来越多的研究组织开始将注意力转移到C-Cl、C-F键的活化上来。而目前的研究显示，富电子的过渡金属配合物在C-Cl、C-F键的活化中表现出显著的优势。与其他过渡金属配合物相比，钴配合物具有价格低廉及对环境更加友好的优势，因此本课题对三甲基膦支持的富电子钴配合物在C-Cl、C-F键活化中的应用进行了探讨，具体内容如下：1．三甲基膦支持的低价态钴的配合物与邻位氯代苯甲醛亚胺的反应芳基氯化物由于其廉价易得，利用其取代昂贵的芳基溴化物、碘化物作为合成原料明显极具经济价值。同时有机氯化物在诸多工业如化工、医药、制革、电子、农药等方面得到广泛应用，导致大量含氯化合物及其合成过程中产生的中间产物被大量地排放到环境中，由于含氯有机物的长期残留性，生物蓄积性，高毒性以及强致癌性，含氯有机物对环境的污染己经引起了各国政府、学术界、工业界和公众的广泛关注，成为一个全球性环境问题。掌握活化C-Cl键的新手段将有助于我们寻找新的氯化、脱氯及C-Cl键功能化途径，有助于我们研究新的合成手段，有助于解决日益严重的含氯化合物对环境污染的问题，有助于环境保护和绿色化学的发展。从经济实用性和绿色化学的角度上看，对利用相对价廉且毒性较低的钴金属体系催化氯代芳烃的功能化的研究极具应用价值。而对氯代芳烃与钴金属配合物的氧化加成产物的研究将有助于为新的钴金属催化体系建立理论模型和提供理论依据。本课题利用CoMeL₄、CoL₄、CoL₃X（X=Cl，Br，I）与2,6-二氯苯甲醛、2-氯苯甲醛与不同的胺合成的一系列希夫碱式化合物发生反应，探索三甲基膦支持的低价态钴的配合物在C-Cl键活化中的反应活性，并合成一系列新的含有[C-Co-Cl]单元的配合物。甲基钴配合物CoMeL₄与邻位取代的希夫碱式化合物（1-5）发生了反应，分离得到了一系列含有五员螯合环的三价钴的配合物（6-10），并对反应产物进行了详细表征。同时发现该系列三价钴的配合物有继续发生偶联反应的趋势，当与空间位阻更大的配体19，20反应时，偶联反应成为主要反应，并通过LC-MS对偶联产物进行了初步的表征。卤化钴化合物CoL₃X（X=Cl，Br，I）与邻位氯代的希夫碱式化合物（2-5）反应，随着反应底物空间位阻大小的不同，得到不同的反应结果。当反应底物位阻较小时，可以得到六配位的三价钴产物11，12，15，16。当反应底物位阻较大时，可以得到五配位的二价钴产物13，14，17，18。CoIL₃无法与空间位阻较大的底物（3-5）发生反应。零价钴配合物CoL₄与N-苯基-2-氯苯甲醛式希夫碱21反应，得到五配位的二价钴产物22。2．对新型含有[C-Co-Cl]单元的配合物的功能化反应的尝试C-Cl键功能化反应的目的是将有机氯化物中的氯原子转化为其它有机官能团，从而使有机氯化物转变成有应用价值的有机化合物，对于环境保护，资源利用和可持续性的发展具有深刻的意义。本课题试图探索一系列含[C-Co-Cl]结构单元的化合物发生功能化反应的可能，研究其反应机理，为开发新的钴催化体系提供依据。配合物12与亲核性较差的三甲基硅乙炔不能发生反应，而与强亲核试剂正丁基锂反应得到的是正丁基锂与苯环上未被活化的C-Cl键发生偶联反应的产物23。在与亲核性适中的苯基格式试剂的反应中，推测配合物12和22都发生了亲核取代反应，其中配合物22的反应中分离出了取代产物24。3．新的含[C-Co-F]结构单元的钴配合物的合成对于C-F键活化的研究具有很大的意义和应用价值。掌握活化C-F键的新手段不仅有助于我们研究合成新的多功能性氟代有机物，而且有助于解决日益严重的含氟化合物对环境污染的问题。在目前进行的研究中，过渡金属有机化合物在碳氟键的活化中的应用取得了一些成果，大多是富电性（electron-rich）的过渡金属配合物活化C-F键的反应。到目前为止，该领域的研究在金属种类、反应条件、选择性和产率等方面仍具有局限性，更没有工业化的例子，同时对反应机理了解也较少。系统地开展芳香族氟化物中C-F键的活化和功能化研究，分离和捕捉可能的活性中间体，探索相关的反应机理可以为开发具有工业应用价值的（催化）反应体系提供理论模型和依据。本课题组曾经报道过甲基钴配合物CoL₄Me可以活化裂解邻位双氟代的芳香族醛联氮化合物的C-F键，通过氧化加成反应生成含有Co-F键的有机钴的配合物。在此研究基础上，本课题试图利用三甲基膦支持的低价态钴的配合物来活化裂解2，6-二氟苯甲醛与不同类型胺生成的一系列希夫碱式化合物的C-F键，并且希望通过反应生成新的有机钴氟配合物。甲基钴配合物CoMeL₄与邻位氟代的希夫碱式化合物（24-27）发生了反应，分离得到了一系列含有五员螯合环的三价钴的配合物（28-31），并对反应产物进行了详细表征。同时CoMeL₄与空间位阻更大的配体（32-34）无法发生反应。零价钴配合物CoL₄与邻位氟代的希夫碱式化合物（25-27）反应，不能够活化断裂C-F键而是生成了通过C=N键与钻进行π配位的仍为零价的钴配合物（35-37）。这是由于N原子的配位以及形成五员环所释放的能量不足以弥补C-F键断裂所需要的能量。4．CoL₄与全氟甲苯的反应由于氟的高电负性使得全氟不饱和化合物双键的亲电性增加，因此，借助富电子的低价过渡金属中心dⁿ（n≥6）可以实现C-F键的活化。本课题设计利用CoL₄与全氟甲苯反应，探索其活化全氟芳烃中C-F键的可能性，并期待生成含有[C-Co-F]单元的钴氟配合物。零价钴配合物CoL₄与全氟甲苯反应，实现了全氟甲苯中双C-F键的活化，并分离出产物配合物39，并获得了其单晶结构。在反应机理研究中，我们已分离出可能的中间物之一配合物38，并获得了其单晶结构。5．对全氟甲苯功能化反应的尝试在对化合物38的反应性质研究过程中，通过与溴苯反应得到了期望的C,C-偶联产物：对苯基氟代甲苯，实现了C-F键的功能化，同时合成了配合物41。虽然这是一个化学整数比的反应，但仍不失为一种合成对位被芳基取代的全氟甲苯衍生物的新方法。本课题对实验过程中获得的新配合物采用IR，¹H，¹³C和³¹PNMR等手段进行了表征，并对其中获得单晶的配合物进一步利用X-ray衍射分析证实结构。更多还原

【Abstract】 Aromatic halides （ArX） are of genuine importance in synthetic organic chemistry. However, the chloro- and fluoroarenes exhibit much lower reactivity due to the inertness of their C-X bonds. It is not surprising, therefore, that attention of numerous research groups has been focused for many years on activation of the C-Cl and C-F bond. A variety of C-Cl and C-F activation reactions that employ electron-rich transition-metal complexes, require comparatively mild conditions, are selective, and afford isolable products are nowknown and catalytic systems have been achieved.Cobalt show their attraction owing to the low prices and envirment friendly. In this doctoral dissertation, application of cobalt complexes supported by trimethylphosphine in C-X（X=F,Cl） bond activation are studied. The mail contents are described as follows:Reactions of cobalt complexes with ortho-chlorobenzaldehydesChloroarenes are certainly the most attractive aryl halides for synthetic applications on an industrialscale, because they are inexpensive and readily available in bulk quantities. Chlorinated organic compounds have been used on a large scale in the chemical, petrochemical, and electronic industries. The disposal of organic wastes containing halogen has become a major environmental and social problem, because most of them are toxic and thermally stable, accumulating in the surroundings for long time periods. The development of a highly efficient,safe alternative technology for activation of C-Cl bonds has been anticipated. The study of activation of C-Cl bond has important significance and value. Mastery of the activation of C-Cl bond will help us to find a new chlorination, dechlorination and C-Cl bond key functional way, and help us study the new chlorinated organic synthesis. Moreover, the chlorine compounds help solve the increasingly serious problem of environmental pollution.Reactions of CoMeL₄、CoL₄、CoL₃X （X=Cl, Br, I） with ortho-chlorinated substrates containing imine anchoring groups are selected to study the reactivity of cobalt complexes supported by trimethylphosphine,and the novel [C-Co-Cl] complexes are expected to be afforded.Reactions of CoMeL₄ with ortho-chlorinated substrates containing imine anchoring groups （1-5）, proceed by oxidative addition of the C-Cl bond to give rise to the mono-ortho-metalated diorgano cobalt（Ⅲ） chlorides 6-10, respectively. The new ortho-chelated cobalt complexes formed by oxidative addition of an aromatic C-Cl bond were isolated and characterized. C,C-coupling reactions have been observed in reactions of [CoMe（PMe₃）₄], LC-MS analysis verified the formation of the respective methyl arene derivatives via C, C-coupling through reductive elimination.Steric hindrance has a marked effect on reactions of CoL₃X （X=Cl, Br, I） with ortho-chlorinated substrates containing imine anchoring groups （2-5）. Reactions of reactants containing small groups afforded mono-ortho-metalated cobalt（Ⅲ） chlorides （11, 12, 15, 16）, while Co（Ⅱ） complexes （13, 14, 17, 18） were formed by reactions with reactants containing bulky groups. C0L3I does not carry out any reaction with 3-5.Reactions of C0L4 with N-phenyl-2-chlorobenzaldehydeamine 21, proceed by oxidative addition of the C-Cl bond to give rise to the mono-ortho-metalated diorgano cobalt（Ⅱ） chloride 22.Functionalizations of the novel complexes containing [C-Co-Cl] fragmentThe functionalization of carbon-chlorine bonds for converting organic chlorides intoindustrially useful materials, is an interesting area of research activity. Enhancementof the poor reactivity of aryl chlorides toward nucleophiles has been one of the most challenging problems and desirable goals for chemists. In this doctoral dissertation, we attempted to study functionalizations of the novel complexes containing [C-Co-Cl] fragment.The mono-ortho-metalated cobalt（Ⅲ） chloride 12 did not carry out any reaction with ethynyltrimethylsilane, while in the reaction with n-butyl lithium, the cholrine in the phenyl ring was replaced by butyl group and afforded the cobalt（Ⅲ） chloride 23. Through the reaction of 12 or 22 with phenylmagnesium, the chlorine was replaced by phenyl group toward nucleophilic substitution and in the reaction of 22, the phenyl cobalt comgplex 24 was isolated.Synthesis of the novel complexes containing [C-Co-F] fragmentThe activation of carbon-fluorine bonds is of great importance in organometallic chemistry and catalyst development because this type of reaction contributes to the fundamental understanding of the reactivity of stable bonds and the selective replacement of F atoms. The use of transition-metal complexes offers another means with which to activate C-F bonds. Reports on C-F activation by firstrow transition metals are rare, and only one example of organocobalt fluorides containing a C-M-F moiety has been described.We have recently reported a cyclometalation reaction involvingcarbon-fluorine bond activation at a cobalt（Ⅰ） center with azine as an anchoring group, which, for the first time, affordsan ortho-chelated cobalt（Ⅲ） complex containing a C-Co-F fragment.Reactions of CoMeL₄ and CoL₄ with ortho-fluorinated substrates containing imine anchoring groups are selected to study the reactivity of cobalt complexes supported by trimethylphosphine, and the novel [C-Co-F] complexes are expected to be afforded.Reactions of CoMeL₄ with ortho-fluorinated substrates containing imine anchoring groups （24-27）, proceed by oxidative addition of the C-F bond to give rise to the mono-ortho-metalated diorgano cobalt（Ⅲ） chlorides 28-31, respectively. The new ortho-chelated cobalt complexes formed by oxidative addition of an aromatic C-F bond were isolated and characterized. No reaction of with reactants containing bulky groups has been carried out. Under the experimental conditions, a C=N bondπ-coordinated Co（O） complexes were obtained when C0L4 was emplyed.Reactions of CoL₄ with octafluorotolueneMost of the reported C-F activation of reactions by transition metals occur at electron-rich dⁿ （n≥6） metal centers via an oxidative addition process. Therefore, reaction of CoL₄ with octafluorotoluene is selected to study the reactivity of cobalt complexes supported by trimethylphosphine with perfluorinated aromatics, and the novel [C-Co-F] complexes are expected to be afforded. Two kinds of products were isolated from the reaction of CoL₄ with octafluorotoluene. It generated one Co （Ⅱ） 39 formed by activation of two C-F bonds in the octafluorotoluene and one Co （Ⅰ） 38 which was obtained as a intermediate.Functionalizations of octafluorotolueneWhen we treated the Co （Ⅰ） 38 with bromobenzene, fluoro substituents in trans position of the CF₃ group was substituted with phenyl group and the expected C-C coupling product was isolated. At the same time the other product Co（Ⅱ） 41 was obtained. It was a stoichiometric reaction, however, it may be a synthetically useful route for the generation of fluoroorganics.All of the now complexes are characterized by IR, ¹H, ¹³C and ³¹P NMR. Structures of some single crystals have been confiemed by X-ray diffraction techniques.更多还原