008-基元反应(插入)PPT演示课件

1,氧化加成和还原消除反应,a）,b）,金属的氧化态及配位数均减少2；配位饱和的高价金属变为配位不饱和的低价金属。,氧化加成反应的特点：,A-B键发生断裂，同时加成到过渡金属上；金属的氧化态及配位数均增加2；配位不饱和的低价金属变为配位饱和的高价金属。,还原消除反应的特点：,2,A=B为C=C、RRC=O、C=N等。:AB为一氧化碳:CO、异氰:CNR、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。,3,Oxidativeaddition/reductiveeliminationprocessesarecentraltoavastarrayofsyntheticallyusefulorganometallicreactions(eg.“Heck”reaction),andoccurbecauseoftheabilityoftransitionmetalstoexistinseveraldifferentoxidationstates,incontrasttonontransitionmetalcompounds,whichusuallyhaveclosedshellconfigurations.Infact,itisthefacileshuttlingbetweenoxidationstatesthatmakestransitionmetalssousefulinorganicsynthesis.,4,5,6,7,氧化加成和还原消除是以Vaska(1968)配合物IrCl(CO)(PPh3)2和Wilkinson配合物RhCl(PPh3)3的发现及反应性研究开始的，对了解催化反应机理非常重要。,8,NotethatmanyoftheseresultintheformationofM-HandM-Cbonds,andinthe“activation”ofarangeoforganicsubstrates.,9,10,Concertedoxidativeadditionsarebestknownfornonpolarsubstrates,eg.H2,andC-Hbonds.,11,OxidativeadditionviaSN2-typeprocessesismostoftenobservedwithstronglynucleophilic,lowvalentmetalsandclassicSN2substratessuchasorganichalidesandtosylates.,12,Collmansreagent,Na2Fe(CO)4,averypotentnucleophile,reactswithRXviaSN2.,13,Competingradicalchainmechanismforoxidativeaddition.Tracesofairsometimespromotethereactionofcomplexeswhichnormallyrequirestrictexclusionofair,andservesasawarningthatthemechanismbywhichareactionproceedsmaybeafunctionofthecarewithwhichitiscarriedout.,14,Nicatalyzedcouplingofarylhalidestobiaryls,whichwasoriginallythoughttoproceedbytwosequentialtwo-electronoxidativeadditions.However,carefulstudiesshowedthiswasnotthecase.Rather,acomplicatedradicalchainprocessinvolvingNi(I)toNi(III)oxidativeadditionisthetruecourseofthereaction.,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,氧化加成和还原消除反应,a）,b）,金属的氧化态及配位数均减少2；配位饱和的高价金属变为配位不饱和的低价金属。,氧化加成反应的特点：,A-B键发生断裂，同时加成到过渡金属上；金属的氧化态及配位数均增加2；配位不饱和的低价金属变为配位饱和的高价金属。,还原消除反应的特点：,34,35,Reductiveeliminationisthereverseofoxidativeadditionandisusuallythelaststepofmanycatalyticprocesses.Itisexceptionallyimportantfororganicsyntheticapplicationsbecauseitisthemajorwayinwhichtransitionmetalsareusedtomakecarbon-carbonandcarbon-hydrogenbonds!,36,Thegroupstobeeliminatedmustoccupycispositionsonthemetal,ormustrearrangetocisiftheyaretrans.,37,Reductiveeliminationcanbepromoted.Anythingwhichreducestheelectrondensityatthemetalfacilitatesreductiveelimination.Thiscanbeassimpleasthedissociationofaligand,eitherspontaneouslyorbytheapplicationofheatorlight.Bothchemicalandelectrochemicaloxidationpromotesreductiveelimination.Additionofstrongp-acceptorligands,suchasCO,maleicanhydride,quinonesortetracyanoethylene,promotestrductiveelimination.,38,39,40,A=B为C=C、RRC=O、C=N等。:AB为一氧化碳:CO、异氰:CNR、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。,41,Migratoryinsertion:Theterm“insertion”issomewhatmisleading,inthattheprocessactuallyproceedsbymigrationoftheadjacentligandtothemetalboundunsaturatedspecies,generatingavacantsite.Insertionsareusuallyreversible.Ifthemigratinggrouphasstereochemistry,itisusuallyret