基元反应(配体的反应)11.12.ppt

A = B为C = C、 RRC = O、C = N等。 :A B为一氧化碳:C O、异氰 :C N R、卡宾:CR2等。,插入反应和消除（反插入）反应,插入反应是指不饱和键插入到M - H键或M - C键中。,特点：金属的氧化态及配位数均没有变化。,Migratory insertion: The term “insertion” is somewhat misleading, in that the process actually proceeds by migration of the adjacent ligand to the metal bound unsaturated species, generating a vacant site. Insertions are usually reversible. If the migrating group has stereochemistry, it is usually retained in both the insertion step and the reverse.,烯烃的插入与 - H消除,1）必须有 - H；,配位,活化,2）M C 和 C H 顺式共平面；（如链状烷基金属有机化合物不稳定， 环状金属杂环化合物不容易发生该消除反应）,3）消除生成双键。,Nucleophilic attack on complexed p-unsaturated hydrocarbons is among the most useful of organometallic processes for organic synthesis, since it is exactly the opposite of “normal” reaction chemistry for these substrates. Nucleophilic attack on 18 electron, cationic complexes has been particularly well-studied. Order of reactivity for Kinetically controlled reactions is as follows. Note that Cp is among the least reactive, and as a consequence, is often used as a spectator ligand.,配位烯烃的反应,Wacker 过程 该反应中生成Pd(0)，用Cu(II)氧化再生Pd(II)， 所生成的Cu(I)再被氧气氧化成Cu(II)，从而完成催化循环。,烯烃本来只能接受亲电进攻，但和金属离子配位后，可以接受亲核进攻。该反应形式上与插入反应类似，但是立体化学是不同的。在此反应中，亲核试剂从金属的另一面进攻烯烃，是反式加成。,Cationic iron complexes of alkynes undergo clean nucleophilic attack from the face opposite the metal, to give stable s-vinyl iron complexes. This process has not been used in organic synthesis to any extent.,From a synthetic point of view, the most important reaction so far has been the Pd(0) catalyzed reaction of alllylic substrates, a process with overall retention (two inv.) of configuration at carbon. In certain rare cases, attack may occur at the center carbon to form metallacyclobutane.,Attack at the central carbon,Site Selectivity,Attack of h5-dienyl complexes,Metal-bound CO is generally reactive towards nucleophiles, providing a major route for the incorporation of carbonyl groups into organic substrates. Neutral metal carbonyls usually require strong nucleophiles such as RLi, and the reaction (a) produces anionic metal acyl complexes (acyl “ate” complexes). Many of these acyl ate complexes are quite stable and can be isolated and manipulated. (O- or C-alkylation of enolates).,Alkoxides and amines attack metal carbonyls, particularly the more reactive cationic ones, to produce alkoxycarbonyl or carbamoyl complexes. Hydroxide ion attacks metal carbonyls to produce (normally) unstable metal carboxylic acids, which usually decompose to anionic metal hydrides and carbon dioxide.,Electrophilic carbene complexes undergo nucleophilic attack at the carbene carbon, resulting in either heteroatom exchange or the formation of stable adduct.,Nucleophilic cleavage of metal carbon s-bonds is another process of interest in organic synthesis, since it is frequently involved in freeing an organic substrate from the metal. Many metal-acyl complexes undergo direct cleavage by alcohols or amines, a key step in many metal-catalyzed acylation reactions.,Although there is a profound reorganization of electrons about the metal, most of these processes result in no change in the formal oxidation states of the metal, differentiating them from the oxidative addition/reductive elimination family reactions. This is because in each case, a formally neutral ligand is converted to a formally mononegative ligand in the process - that is, nucleophilic attack reduces the ligand, not the metal. Only with few exceptions.,