金属有机化合物的基元反应

金属有机化合物的基元反应,一般有四类基元反应1配体的配位和解离反应2氧化加成反应和还原消除反应3插入反应和消除反应（反插入反应）4和金属络合的配体被进攻的反应,插入反应与反插入反应,插入反应为不饱和键插入到M-H,M-C之间的反应。它主要有两种类型：1AB分子插入后分别与金属和R基团相连。2AB分子插入后A同时与金属和R基团相连,Definitions;MigratoryInsertion-MI,NumberingdescribeswhichatomsoftheinsertedligandarebondedtoMandXaftertheinsertionOppositeofinsertioniselimination(or“deinsertion”inUSA),A=BisoftenCO,A=Bisoftenanalkene,Definitions;Elimination-E,ThisisthesameasthelastslidewitharrowsgoingbackwardsNamedbywhichatomcontainsthemigratinggroupUnfortunatelytheterm“1,1-elimination”etc.israrelyused,eventhoughitstheoppositeofa1,1-insertion!,1,1-MigratoryInsertionanda-EliminationStereochemistryatcarbon,ConfigurationatastereogeniccarbonisretainedSameappliestothereverse,i.e.a-elimination,CO的插入反应:,由于CO和金属配位，金属的d电子向CO的反键轨道反馈，导致M-R键的削弱，同时CO中的碳-氧键也被削弱。插入反应这一过程有两种可能的途径1CO插入到M-R键中2与金属相连的R基团迁移到CO上,1,1-MigratoryInsertionanda-EliminationMechanisticquestions,Theabovereactionhasbeenstudiedindetail,andmuchisknownaboutthemechanism,研究表明是按R基团迁移的的途径进行的R基团迁移不可能得到4，研究表明产物1：2：3的比率为1：2：1，而且没有4生成。,1,1-MigratoryInsertionanda-EliminationWheredoestheCOcomefrom?,COthatisinsertedintoMn-Mebondis“unlabelled”,soitmusthavecomefromwithinthecomplex(i.e.mechanismisintramolecular)The13COintheproducthasremainedcistoacylandhasnotmovedatalltothetranssite.Inotherwords,thereactionisunderkineticcontrol(I.e.thefirst-formedproductisobserved).,1,1-MigratoryInsertionanda-EliminationIsthisacisprocess?,The13Clabelledacylproductwassynthesisedbyanalternativerouteshownabove,andwasthenheatedtopromoteeliminationOnlythecisisomerwasobserved,thereforeinthereversereaction(the1,1-MI)themethylgroupmustbereactingwithaCOthatiscistoit.ThislogicreliesonthePrincipleofMicroscopicReversibilityInasinglestepreversiblereaction,themechanismoftheforwardreactionisthesameasthatofthereversereaction,1,1-MigratoryInsertionanda-EliminationWhichMoves?TheCOortheMe?,Thetwoproductsarethesame,sohowdowetellwhichmechanismishappening?,Considerthetwopossibilities,1,1-MigratoryInsertionanda-EliminationInsertionorMigration?,ExpectedproductofCO“deinsertion”(anon-13Cproductisalsoformed),Expectedproductsofmethyl(de)migration(anon-13Cproductisalsoformed),Experimentshowsmixtureofcisandtransinratio2:1soALKYLMIGRATIONisthemechanism,Studyreversereaction,thenapplyPrincipleofMicroscopicReversibility,ThereactiononSlide15isalsoconsistentwithalkylmigration,notCOinsertion,“COmoves”,“Memoves”,脱羧反应：CO插入的逆反应,烯烃的插入和-H消去,烯烃的插入反应的前提条件是烯烃与金属中心离子配位反馈，导致烯烃的活化和M-R键的削弱，结果生成C-R键和新的C-M键，这种加成一般是顺式加成,1,2-MigratoryInsertionandb-EliminationDefinitionsandconditions,ChangeinCN=-1for1,2-MI,butnochangeinOSFreecoordinationsiteneededforb-eliminationBothforwardandreversereactionsgothroughaplanartransitionstate,CN=n+2,1,2-migratoryinsertion,1,2-orb-elimination,CN=n+1,coplanar,-H消去一般有以下4步1，有空配位-配体解离2，M-C和C-H共平面3，消除生成双键4，生成的双键解络,1,2-MigratoryInsertionandb-EliminationPreventingb-elimination,Althoughb-eliminationisslightlyendothermic,itisacommondecompositionpathwayforalkylsCanbepreventedbynothavinganyb-hydrogens(averyeffectivestrategy!)saturatingthecoordinationsphere(i.e.nofreecoordinationsiteavailable)preventingplanarisationmetallacycle,orunstablealkeneproductSometimes,the“transitionstate”isanintermediate;givingtheagosticinteraction(see“organometallichypertextbook”),和金属络合的配体被进攻的反应,具有不饱和键的化合物通过不饱和键和金属配位后被活化。过渡金属与烯烃、N2、CO、CO2等小分子形成配位键后，弱化氮氮三键或碳氧三键，这是小分子活化的基础。,烯烃，炔烃与过渡金属配位后，由于金属原子对烯烃，炔烃反键轨道的电子反馈，使双或三键活化，可接受外来亲核试剂的