配位化學課件Coordination-Compound3

STEREOCHEMISTRYOFCOMPLEXESPARTTHREESTEREOCHEMISTRYOFCOMPLEXESIntroduction3-1.GeometryofCoordinationCompounds3-2.IsomerisminMetalComplexesPARTTHREESTEREOCHEMISTRYOFCOMPLEXESSTEREOCHEMISTRYOFCOMPLEXES3-4.OpticalIsomerism3-5.OtherTypesofIsomerism3-3.GeometricalIsomerismPARTTHREESTEREOCHEMISTRYOFCOMPLEXESINTRODUCTIONIntroductionStereochemistryisthemostimportantbranchofchemistryconcernedwiththestructuresofcompounds.Sometimes,itisausefulvisualaidtouseasimplestickmodelstohelpyoustudythethree-dimensionalstructures,especiallythecomplicatedones.Somepeoplewouldthinkthatthissubjectbelongsinthescopeoforganicchemistry.INTRODUCTIONInfact,theattentionoforganicchemistryismainlyfocusedonthecarbonatomanditssurroundingfourgroups,andonlys,p,

orbitalsareusedfortheformationofbonds.However,ininorganicchemistry,especiallyincoordinationcompound,itisoftennecessarytoconsidernotonlythes,porbitals

butalsod,evenforbitals.Therefore,thestructuresarerelativelysimple.

INTRODUCTION

Manymetalsarefromthefourthtotheseventhrowelements,oftenthecoordinationnumbersbeingfromfourtotwelve.Sothestructureofcoordinatecomplexesaremorecomplicated.

3-1.GeometryofCoordinationCompounds

一.Typesofgeometry3-1.GeometryofCoordinationCompoundsManyobservedmetalcomplexeshaveagreatvarietyofstructures.

Forexamples(seeFigure3-1):Silvercomplexes——areoftenlinear一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsBerylliumcomplexes——areusually

tetrahedralIroncarbonylcompounds——havetrigonalbipyramidCobalt(Ⅲ)complexes——areinvariablyoctahedral;Tantalum(鉭－tan)formsaneight-coordinatedcomplex

一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds

二.ThecommongeometryAlthoughavarietyofcoordinationnumbersandstructureshavebeenobservedinmetalcomplexes,theonlycommoncoordinationnumbersare

fourandsix；

thecommonstructurescorrespondingtothesecoordinationnumbersare

tetrahedral，squareplanarandoctahedral,respectively.

Inastudyofmetalcomplexesitsoonbecomesclearthattheoctahedralstructureisbyfarthemostcommonoftheseconfigurations.一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds

Aninterestingandusefulapproachtothepredictionofstructureofcompoundsinwhichthecoordinationnumberofthecentralatomisknownisgivenbythe

VSEPR

(valenceshellelectron-pairrepulsion)theoryofGillespieandNyholm.

Oneconclusionfromthistheoryisthatingeneral,four-andsix-coordinatedcomplexeswillbetetrahedralandoctahedral,respectively.

一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds

三.

Jahn-Tellerdistortion(briefly)Complexesoftransitionmetalssometimesdeviatefromthisrule,andthedeviationcanbeattributedtothepresenceofdelectrons.Crystalfieldtheory(CFT)providesperhapsthesimplestexplanationoftheeffectofdelectronsonthestructureofcomplexes.一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsTheCFTclaimsthatdorbitalshaveaspecificgeometryandorientationinspaceandthatdelectronswillresideintheorbitalsthatarefarthestfromneighboringatomsormolecules.

Thepresenceofdelectronsinsix-orfour-coordinatedcomplexestendstocausedistortionoftheexpectedoctahedralortetrahedralconfiguration.

Thedistortionarisesbecauseligandswillavoidthoseareasaroundametalioninwhichthedelectronsreside.一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsForexample,in[Ti(H2O)6]3+;[Cr(H2O)6]2+;[MnF6]3-;…etc.Theiroctahedralshapesarelikethefollowingshapes(Figure3-2),whicharecalledJahn-Tellerdistortions.Wehavelearneditbefore.

Thedistortionsthatresultfromthepresenceofdelectronsin"octahedral"complexesaresummarizedinTable3-1一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsWehaveconsideredthedistortionstooctahedralstructurethatresultfromthepresenceofdelectrons.

Tetrahedralstructuresarealsoobservedinmetalcomplexes,however,theyarelesscommonthanoctahedralanddistortedoctahedralconfigurations.Iffourligandssurroundametalatom,atetrahedralstructureisexpected.

Thepresenceofdelectronsmaythenresultindistortionofthetetrahadron.一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsTwoexceptionsmustbenoted:(i)Aswehaveseen,four-coordinatedlow-spind8complexesaresquareplanar,asarefour-coordinatedd9andhigh-spind4complexes.

(ii)Metalcomplexescontaining0,5unpaired,and10delectronsareundistorted,aswasnotedpreviously.

一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsAsinoctahedralcomplexestheplacementofelectronsinorbitalspointingbetweenligandsprovidesnoobservabledistortion.

Theremainingtetrahedralsystems,d3,d4,d8,andd9,...，shouldexhibitmarkedJahn-Tellerdistortions.Thustetrahedraldl,d2,d6,andd7complexesappeartobeundistorted.一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsVeryfewexamplesofcompoundsofthistypeexist,however.

Low-spintetrahedralcomplexesneednotbediscussed,sincetherearenoexamplesofsuchcomplexes.

ThetetrahedralCFsplitting(Δt)isapparentlytoosmalltocausespinpairing.一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds

四.ThepredictionofgeometryAlthoughitispossibletopredictfairlyaccuratelythestereochemistryofcomplexionsinwhichthecoordinationnumberofthecentralatomisknown,itismuchmoredifficulttopredictthecoordinationnumberofthecentralatom.

Largecoordinationnumbersarefavoredbytheelectrostaticattractionofnegativelychargedligands(orpolarmolecules)forapositivemetalion.

一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompounds

Covalentbondingtheories

predictingeneralthat

thegreaterthenumberofbondsformedtoanelement;thegreateristhestabilityoftheresultingcompound.Thetendencyforlargecoordinationnumbersisopposedby

steric（空間）andelectrostatic(orPauli)repulsionbetweenligands.

Nosimpleschemehasbeenpresentedtomakepredictionsfromthesecriteria.

一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-1.GeometryofCoordinationCompoundsItmightbenoted,however,that:(i)

Thefirst-rowtransitionelementsarefrequentlysix-coordinated.(ii)

Four-coordinationisobservedprimarilyincomplexescontainingseverallargeanions,suchasClˉ,Brˉ,Iˉ,andO=,orbulkyneutralmolecules.

(iii)

Thesecond-andthird-rowtransitionelementsexhibitcoordinationnumbersaslargeaseight.

一.Typesofgeometry二.Thecommongeometry三.

Jahn-Tellerdistortion(briefly)四.Thepredictionofgeometry3-2.ISOMERISMINMETALCOMPLEXES3-2.ISOMERISMINMETALCOMPLEXES

Moleculesorionshavingthesamechemicalcompositionbutdifferentstructuresarecalled

isomers.

Thedifferenceinstructureisusuallymaintainedinsolution.

3-2.ISOMERISMINMETALCOMPLEXES3-2.ISOMERISMINMETALCOMPLEXES

Isomersare,therefore,notmerelydifferentcrystallineformsofthesamesubstance;forexample,therhombic(斜方的)andmonoclinic（單斜的）formsofsulfurarenotisomers.

Metalcomplexesexhibitseveraldifferenttypesofisomerism;thetwomostimportantaregeometricalandoptical.Othertypesalsowillbedescribed,andspecificexamplesforeachwillbegiven.3-2.ISOMERISMINMETALCOMPLEXES3-2.ISOMERISMIN…

Onefacttonoteisthat,ingeneral,onlycomplexeswhichreactslowlyarefoundtoexhibitisomerism.Thisisbecausecomplexesthatreactrapidlyoftenrearrangetoyieldonlythemoststableisomer(ChapterⅥ).3-2.ISOMERISMINMETALCOMPLEXES3-3GEOMETRICALISOMERISM

一.introductionInmetalcomplexestheligandsmayoccupydifferenttypesofpositionsaroundthecentralatom.

Sincetheligandsinquestionareusually

either

nexttooneanother(cis)

or

oppositeeachother(trans),thistypeofisomerismisoftenalsoreferredtoas

cis-transisomerism.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISM

SuchisomerismisnotpossibleforcomplexesofCN=2or3orfortetrahedralcomplexes.BecauseInthosesystems,allcoordinationpositionsareadjacenttooneanother.

However,

cis-transisomerismisverycommonforsquareplanarandoctahedralcomplexes,theonlytwotypestobediscussedhere.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMMethodsofpreparationandreactionswillbediscussedlater.

二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.Platinum(Ⅱ)complexesareverystableandslowtoreact;amongthemarenumerousexamplesofsquareplanargeometricalisomers.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMNodoubtthebestknownofthesearecis-andtrans-[Pt(NH3)2Cl2],IandlI.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMThechemistryofplatinum(II)complexeshasbeenstudiedextensively,particularlybyRussianchemists.

Manycompoundsofthetypescis-andtrans-[PtA2X2],[PtABX2],and[PtA2XY]areknown.(AandBareneutralligandssuchasNH3,py,P(CH3)3,andS(CH3)2；XandYareanionicligandssuchasCIˉ,Brˉ,Iˉ,NO2ˉ,andSCNˉ.)

Isomerscanbereadilydistinguishedbyx-raydiffractiontechniques.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISM

Othermethodsofdeterminingthestructuresofgeometricalisomersarediscussedlater.Afewcompoundsofplatinum(Ⅱ)containingfourdifferentligands,[PtABCD],areknown.RealizingthateitherB,C,orDgroupsmaybetranstoA,itisapparentthattherearethreeisomericformsforsuchacompound.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMThefirstcomplexofthistypetobeobtainedinthreeformswasthecation[PtNH3(NH2OH)pyNO2]+,whichhasstructuresIII,Ⅳ,andV.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISM

Inordertodesignatethestructureofaparticularisomer,itisconvenientto

placethetwosetsoftransligandsinseparateangularbrackets(<>).

Forexample,[M<AB><CD>]signifiesthatAandBareintranspositions,asmustbeCandD.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISM

Individualisomerscanbenamedby

thenumbersystemorbyusingthetransprefix,whichimpliesthatthefirsttwoligandsinthenameareintranspositions.Itfollowsthatthelasttwoligandsnamedarealsoinpositionstranstoeachother.Geometricalisomerismisalsofoundinsquareplanarsystemscontainingunsymmetricalbidentate(雙齒)ligands,[M(AB)2].

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISM

Glycinate(甘氨酸根)ion,NH2CH3COOˉ,issuchaligand；itcoordinateswithplatinum(Ⅱ)toformcis-andtrans-[Pt(gly)2]havingstructuresVIandVII.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMItisnotnecessarythattheattachedligandatomsdiffer；allthatisrequiredis

that

thetwohalvesofthechelatering（螯合環(huán)）bedifferent.

三.

GeometricalisomerisminoctaheclralcompoundsGeometricalisomerisminoctaheclralcompoundsisverycloselyrelatedtothatinsquareplanarcomplexes.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMAmongthemostfamiliarexamplesofoctahedralgeometricalisomersare:theviolet(cis)andgreen(trans)formsofthedichlorotetraamminechromium(III)cations,whichhavestructuresⅧandIX.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMHundredsofisomericcompoundsofthetypes[MA2X2],[M(AA)2X2],[MA4XY],and[M(AA)2XY],whereM——Co(III),Cr(Ⅲ),Rh(Ⅲ),Ir(Ⅲ),Pt(Ⅳ),Ru(II),andOs(II),havebeenpreparedandcharacterized.

Afewisomersofthetype[MA3X3]areknown；thesecompoundscanformonlytwogeometricalisomers.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMForexample，theisomersof[Rh(py)3Cl3]havethestructuresXandⅪ.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMEitherthelikegroups

occupythecornersofoneoftheoctahedralfaces(cisisomer)ortheydonot(transisomer).

Thelargestnumberofgeometricalisomerswouldexistforacomplexofthetype[MABCDEF],whereineachligandisdifferent.

Suchaspeciescanexistin15differentgeometricalforms(eachformwouldalsohaveanopticalisomer,seelater).

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMThestudentmaywishtodrawallofthepossiblestructures.Theonlycompoundofthistypethathasbeenpreparedis——

[Pt(py)(NH3)(NO2)(Cl)(Br)(I)].

Itwasobtainedinthreedifferentformsbutnoattemptwasmadetoisolateallfifteenisomers.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISM

Unsymmetricalbidentateligands

giverisetogeometricalisomersinmuchthesamewayaswasdescribedearlierforsquareplanarcomplexes.Forexample,thecis-transisomersoftriglycinato-chromium(Ⅲ)havethestructuresXIIandXIII.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-3GEOMETRICALISOMERISMEachofthesecomplexesisopticallyactive,asisdiscussedinthefollowingsection.

一.introduction二.cis-transisomerisminsquareplanarsystemsofPt(Ⅱ)complexes.三.

Geometricalisomerisminoctaheclralcompounds3-4.OPTICALISOMERISM

一.IntroductionIthasalreadybeennecessarytomakesomereferencesorremarkstothephenomenonofopticalisomerism.

Abriefdiscussionisprovidedhere,alongwithafewadditionalexamplesofopticallyactivemetalcomplexes.

3-4.OPTICALISOMERISM一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMTheclassicalexperimentsin1848ofLouisPasteur,oneofthemostillustrious(杰出的)andhumaneofallmenofscience,showedthatsodium

ammoniumtartrate（酒石酸）existsintwodifferentforms.Opticalisomerismhasbeenrecognizedformanyyears.

Crystalsofthetwoformsdiffer,andPasteurwasabletoseparatethem

bythelaborioustaskof

handpicking.一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMAqueoussolutionsofthetwoisomershadthepropertyofrotatingaplaneof

polarizedlight(abeamoflightvibratinginonlyoneplane)eithertotherightortotheleft.

Becauseofthispropertytheisomersaresaidtobeopticallyactiveandarecalledopticalisomers;oneisdesignatedasthedextro(d)isomerandtheotherasthe

levo(l)isomer.一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMTheextentofrotationoftheplaneofpolarizedlightbythetwoisomersisexactlythesame;however,thedextro

isomerrotatestheplaneoflighttotheright,thelevo

isomertotheleft.

Itfollowsthat

therotationscanceleachotherinsolutionscontainingequalconcentrationsofthetwoisomers.Suchad,lmixtureiscalleda

racemicmixture(外消旋混合物).Sinceitssolutiondoesnotrotateaplaneofpolarizedlight,itisoptically

inactive.一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISM

二.Judgmentofaopticallyactivecomplex

Whatpropertyofamoleculeorionrenders

it

opticallyactive?

Theanswerisasymmetry(lackofsymmetry).Thesymmetryrelationshipofopticalisomersissimilartothatoftherightandlefthands,orfeet,orgloves,orshoes.

一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMThereisarathersubtledifferencebetweenthestructures;therelativepositionsofthethumbandfingersoneachhandarethesame,yetthetwohandsaredifferent.Oneisthemirrorimageoftheother.

Ananalogoussituationmustexistifamoleculeorionistobeopticallyactive.一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMInorderforamoleculeoriontobeopticallyactive,itmustnothaveaplaneofsymmetry,i.e.,

itshouldnotbepossibletodividetheparticleintotwoidenticalhalves.

Anothertestthatcanbeappliedinattemptingtodecidewhetheragivenstructurewillbeopticallyactiveisto

compareitwithitsmirrorimage.

Ifthestructureanditsmirrorimagearedifferent,

thestructurewillexhibitopticalactivity.一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISM

三.Enantiomersand

raeemization

Thedandlisomersofagivencompoundarecalledenantiomorphsorenantiomers

(對映體)，whichmeanoppositeforms.

Ingeneral,theyhaveidentical

chemicalandphysicalproperties.一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMTheydifferonlyinthedirectioninwhichtheyrotateaplaneofpolarizedlight.Arathersimpleinstrumentknownasa

polarimeter（旋光儀）isusedforthispurpose.

Thispropertypermitsthemtobereadilydetectedandtobedistinguished.

一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMItisinterestingtonotethatsometimesthephysiologicaleffectsofenantiomersareprofoundlydifferent.

Thusthel-nicotinethatoccursnaturallyintobaccoismuchmoretoxicthanthe

d-nicotinethatismadeinthelaboratory.Specificeffectssuchastheseareattributedtoasymmetricreactionsitesinbiologiealsystems.

一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMSinceenantiomersaresosimilar,andsinceinchemicalreactionsthetwoformsarealwaysproducedinequalamounts,specialtechniquesarerequiredtoseparatethetwo.

Thisseparationprocessiscalledresolution(拆分).

一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandraeemization四.Examples3-4.OPTICALISOMERISMSomeresolutionmethodswillbedescribedlater.

Often,asingleopticalisomerwillrearrangetogivea

racemicmixture.

Theprocessiscalled

racemization(外消旋作用).一.Introduction二.Judgmentofaopticallyactivecomplex三.Enantiomersandracemization四.Examples3-4.OPTICALISOMERISM

四.ExamplesThesimplestpossibleexampleofanasymmetricmoleculeisone

withatetrahedralstructurewhereinthecentralatomissurroundedbyfourdifferentatomsorgroups.Therearemanyexamplesofsuchmolecul