Class Presentations - full.pptx
eli.zysman-colman@st-andrews.ac.uk can be seen below in terms of the respective pKa values ... hydrolyse at pH 7 and passes through specific.
CH3514 – Physical Inorganic Chemistry Page 1 of 43
There are three types of orbital interactions between ligands and metals which define the The pKa can be derived from the pH of the water and the.
TECHNIQUE: Extraction liquide-liquide
chargés sont plus solubles dans l'eau que dans les solvants organiques d'où l'intérêt de connaître le pKa des produits et le pH des solutions.
FACULTÉ DES SCIENCES DÉPARTEMENT DE CHIMIE CHM 302
L'examen est noté sur 80 et compte pour 40% de la note finale. 1 pt pour le pKa 1 pt pour les 2 réactions et 1 pt par proposition de pH.
BRNO UNIVERSITY OF TECHNOLOGY
Ing. Jozef Kraj?ovi? Ph.D. for his guidance
New derivatives of 12
https://core.ac.uk/download/pdf/215531285.pdf
Multifaceted aspects of charge transfer
Jul 4 2020 Espinoza
Untitled
1.30-1.45 L3 Welcome and Introduction: David Cole-Hamilton reactions of Rh and Ir NHC complexes: attenuation and ... Dr. Eli Zysman-Colman.
rsc.li/pccp
Jan 7 2017 Royal Society of Chemistry peer review process and has been ... proton transport and pH gradients are conserved for energy.
Session of Inorganic Chemistry
and conditions such as temperature solvent
pH et pKa - Zysman-Colman
Définition La définition que nous utiliserons : Brønsted-Lowry (1923) Un acide est une espèce qui a tendance à perdre un proton [H2O] est très grand et ~constant Constante d’acidité Plus la valeur de pKa est faible plus le Ka est grand plus l’acide est fort 3 pKa = -log Ka Table de pKa http://evans harvard edu/ pdf /evans_pKa_table pdf 4
CH3514-PhysicalInorganicChemistryPage2of431.INTRODUCTION:CoordinationChemistryofComplexesThismodulefollowsfromthetransitionmetalschemistrymoduleofCH2501.Here,therewillbeafocusonunderstandingthethermodynamicsandkineticsofreactionsinvolvingmetalaquacomplexes.Inparticular,conceptsrelatingtostepwiseandglobalequilibriumconstantsandtheirrelationshiptothefreeenergyofformationwillbediscussed.Thechelateeffectwillbeexploredasitpertainstothethermodynamicstabilityofthecomplexes.Kineticlabilityanditslinktothermodynamicstabilitywillalsobeinvestigated.Finally,therewillbeamoredetailedexplorationofbothmolecularorbitaltheoryandligandfieldtheory.2.MOTheoryBeforewecanunderstandMOdiagramsandbondingincomplexes,wemustunderstandthenatureofthefrontierMOsofligands.Therearethreetypesoforbitalinteractionsbetweenligandsandmetals,whichdefinetheligandtype:• s-donors• p-donors• p-acceptors2.1MOTheory:s-DonorLigandsTheseligandsdonatetwoe-sfromanorbitalofσ-symmetry.Examplesinclude:H-,CH3-,NR3,PR3,OH2.2.1.1MOTheory:s-DonorLigands:NH3Let'slookmorecloselyattheMOdiagramofNH3asaprototypics-donor.ThismoleculeisC3-symmetric.Thesymmetryadaptedlinearcombinations(SALCs)ofatomicorbitalsareshownbelow.HOMOLUMO[Ru(bpy)3]2+
CH3514-PhysicalInorganicChemistryPage3of43Recallthatonlyorbitalsofthesamesymmetrycancombinetoformnewmolecularorbitals(MOs),inwhatisalsotermedlinearcombinationsofatomicorbitals(LCAOs).Sotheallin-phaseSALCofa1symmetrycanformtwocombinations,onewiththeN2pzandonewiththeN2sorbitals.EachofthetwoSALCsofesymmetry(bothcontainingonenodeandsohigherinenergythantheSALCofa1symmetry)cancombinewithoneoftheothertwoN2porbitals,asshownbelow.Noticethatineachcase,thephasingoftheorbitalsaligns(lightwithlightanddarkwithdark).Withthesecombinationsinhand,wenextneedtoconstructtheMOdiagram.Rememberthat:• Thegreatertheoverlap,thegreaterthesplitting• Thecloserinenergybetweenthetwosetsoforbitals,thegreaterthesplittingRecallalsothattheHOMOisusedforbondingtothemetalanditisinthiscaserelatedtothelonepaironNinas-orbital.TheMOdiagrampredictsoccupiedMOsofthreedifferentenergies,whichisborneoutexperimentallybyphotoemissionspectra(PES).Nonodes1node3H'sNa1e
CH3514-PhysicalInorganicChemistryPage6of43WhenanalyzingNH2-,oneofthethreehydrogenatomsisreplacedwithalonepair.TheresulthereisastrongdestabilizationoftheMOofformallyexsymmetryaswehaveremovedabondinginteractionbetweentheN2pxorbitalandoneofthethreehydrogenatoms.TheMOthatformallywasofa2symmetrydoesn'tchangeenergywiththereplacementofoneofthethreehydrogenatomswiththelonepairasthe2pzorbitalisorthogonaltotheplaneoccupiedbythelonepair.2.3MOTheory:p-AcceptorLigandsThisclassofligandsdonatese-sfromaσorbitalandtheseligandsaccepte-sfromthemetalintoanemptyπ*orbital.COisthearchetypeofthisligandclass.Otherπ-acceptorsareNO+,CN-,CNR,H2,C2H4,N2,O2,PR3,BR2.WeanalyzedtheMOdiagramofCOindetailinCH2501.TheHOMOofCOisthelonepaironcarbonandthisiswhatbindstothemetal.TheLUMOofCOisoneofthetwodegeneratep*orbitals.Itisintothisorbitalthatthemetalback-donatesintotheligand.2.4MOTheory:GeneralConceptsSomeimportantpointstorememberregardingMOdiagrams.TheM - LatomicorbitalmixingbetweentwoatomsMandLisproportionaltotheoverlapbetweenthetwoatoms(SML).Owingtomoredirectionalbonding(greateroverlap)alongtheseriesSML(σ)>SML(π)>SML(δ),whichleadstogreatersplittingalongtheseriesofbondingandantibondingorbitals(therefore,s-bondstendtobemorestabilizedandtheantibondingcombinationtendstobemoredestabilizedthanp-bondsandp-antibondingcombinations).M-Latomicorbitalmixingisinverselyproportionaltoenergydifferenceofmixingorbitals(i.e.ΔEML).Sothecloserinenergythetwosetsoforbitals,thegreaterthemixing(andthegreaterthesplittingofthebondingandantibondingcombinations).OnlyorbitalsofcorrectsymmetrycanmixandthetotalMOs=sumoftheprecursororbitals.Thislastpointisextremelyimportant.Formostmetalcomplexes,theorderoftheenergiesoftheligand-basedandmetal-based
CH3514-PhysicalInorganicChemistryPage7of43orbitalsELandEMalmostalwaysis:s(L)
E(NH2-)>E(OH-)• Morbitalenergydecreaseswithincreaseoxidationstateofmetal,asyougodowntheperiodictableandasyougofromlefttorightontheperiodictable,whichisreflectiveintheionizationenergyofthemetal(seebelow)-recallthatthereisacontractionintheionicradiumacrosstherowduetoinefficientshieldingofthed-orbitalsbyd-electrons.3LIGANDFIELDTHEORY(LFT),REVISITED.NowthatwehaveinvestigatedtheMOdiagramsoftheligands,letusnowtryandunderstandinmoredetailLFT,whichistheinteractionofligandMOswithmetalAOs.WhatisLFT?LFTisamorecompletetheoryofbondingwithincomplexes,andincorporatesaspectsofcrystalfieldtheorywithMOtheory.Ligandfieldtheoryattemptstoincorporatetheoverlapofmetal-baseddorbitalswithligandorbitalsofsuitablesymmetry.Thisapproachtriestoexplain,amongotherthings,theeffectofdifferentligandsonΔo.2nd130914141592150915611644175219583rd265028283056325129563231348939544th41734600490050205510511454045683
CH3514-PhysicalInorganicChemistryPage8of43LFTanalysesbondingofmetals,panddorbitalswithSALCsoftheligands,whichareusuallyformedofsandporbitals.Therearetwoprincipalbondingbonds,similartowhatwehaveseenpreviously.Theyares-andp-bonding.Newbondingbetweentwometalscanalsohaved-symmetry(seeCH2501notes).3.1LIGANDFIELDTHEORY(LFT),REVISITED-OctahedralComplexes.Sigma(s)bonding• Neutralligands(e.g.,NH3)oranionicligands(e.g.,F-)possesslonepairsthatcanbondtometal-basedorbitals(s,px,py,pz,dxy,dyz,dxz,dx2-y2,dz2)withs-symmetry• InanOhcomplex,6SALCsofthe6ligands-symmetryorbitalscanbeformed• MOsfortheresultingcomplexareformedbycombiningtheligandSALCsandthemetal-basedd-orbitalsofthesamesymmetrytype(whichwillbeofegsymmetry)• With6SALCscombinedwiththemetalMOs,wewillget6bondingand6antibondingMOs-nowcalledligandgrouporbitals(LGOs)• TheresultingMOdiagramnowgetspopulatedwiththeelectronsaccordingtotheAufbauprocess,PauliexclusionprincipleandHund'sruleAboveyoucanseethedifferentSALCsinteractingwiththemetals(left),p(middle)andd(right)orbitals.FortheLigandSALCs,thesearecomposeduniquelyofsorbitalsforthesakeofsimplicityabovebutareshownassp3hybridorbitalsbelow.Thedxy,dxzanddyzorbitalsdonothavetheappropriatesymmetrytocombinetoformnewLGOs.Inaddition,theligandSALCScaninteractwiththemetalsandporbitals.IfwenowlookatthecorrespondingMOdiagram(below),weseethatthenewbonding/antibondingMOcombinationofthedx2-y2anddz2orbitalsarenowcalledegandeg*,respectively.TheegMOisveryligandbased(itiscloserinenergytotheligandSALCs)whiletheeg*ismoremetalbased.Thethreedorbitalsconstitutingthet2gsetarenownon-bonding.Noticethatthed-orbitalsplittingpatternisexactlythe
CH3514-PhysicalInorganicChemistryPage25of43AnotherexampleinvolveschelationofFe3+.Apotentiallyfatalconditioncalledhemosiderosisoccurswhenthenaturallyoccurringironcarrierproteintransferrinbecomessaturatedandironbecomesdepositedwithinthebody.Incasesofsevereironoverload,depositionintheheart,liverandendocrinesystemsleadstofunctionalimpairmentoftheseorgans,andreducedlifeexpectancy.ThereexistotherclinicallyprovenagentsfortheremovalofFe3+fromthebody,suchasdeferoxamineanddeferiproneandtheexamplesshownbelow,whichareallagentsbasedonEDTAderivatives.NoteineachexampletheaffinityofthehardFe3+forhardOdonors.8.STABILITIESOFOXIDATIONSTATES.Thehigheroxidationstatesbecomemoreoxidisingandtheloweroxidationstateslessreducingasonemovestotherightofthed-block.Whyisthisso?Itisduetothepoorshieldingofthenucleusbytheadditionofsuccessived-electrons(dblockcontraction),wheretheeffectivepositivechargefeltbyanouterelectronincreasesfromlefttoright.Thishastwoconsequences:• Generaldecreaseinionicradiusfromlefttotheright.• Valenceelectronsbecomehardertolose/sharethemoretotherightonegoes.Therefore,thehigheroxidationstatesbecomemoreoxidizingandthelowerstateslessreducing.Buthowdowetrulydefinetheterm"oxidationstate"?Innomenclaturetermsthisisdonebyassumingoctetconfigurationstodefinethechargeontheatomsattachedtothemetalintheionorcomplex.Thetablebelowprovidessomeexampleswithdifferentmetalsandligandforwhatthecalculatedoxidationstateonthemetalwouldbe.ComplexLigandTotalChargeonLigandOverallChargeonComplexOxidationStateofMetal
CH3514-PhysicalInorganicChemistryPage26of43[Mn(OH2)6]2+H2O0+2IIMnO4-O2-8--1VII[Fe(CN)6]4-CN-6--4II[Co(NH3)4(O2CR)Cl]+NH3RCO2-Cl-01-1-+1IIIInreality,oxidationstatesareaformalismandareonlytrueiftheM-Lbondingishighlyionic(electrostatic).e.g.,[Mn(OH2)6]2+whereMntrulyisMn2+whereindependentevidenceexistsfromopticalspectroscopy&magnetismthatMn2+ishighspind5.Butwhataboutthecaseof[MnO4]-wheretheMn-Obondsarehighlycovalent(Mn-Obondlengthislessthansumofionicradii).Sowherenowaretheelectrons(seethethreeresonancestructurestotheleft)?Hereopticalspectroscopyandmagnetismarelessinformative:• TheabsorptionspectrumisdominatedbyOàMnligand-to-metalchargetransferbands• ThecomplexisdiamagneticSowewriteasMnVII(O-II)48.1QUANTIFICATIONOFOXIDIZINGANDREDUCINGSTRENGTHS.WeknowthatMnO4-isapowerfuloxidantand[Cr(OH2)6]2+isapowerfulreductant.Buthowdowequantifyoxidisingandreducingstrength?Theanswer:Usingascaleofstandardredoxpotentials,Eo.Thesearebestenvisagedaspartofanelectrochemicalcell-thedrivingforceinabattery(showntotheright).ConsidertheinteractionofCu2+/CuandZn2+/ZnintheDaniellCell.ThereactionisspontaneousasDGoisnegative.Thiselectrochemicalcellcanbethoughtofastwohalfreactions.Thepotentialdifference,Eocellismeasuredbythevoltmeter.Thepotentialdifference,Eocellisdefinedasthestandardcellpotentialunderstandardconditions,whichare:
CH3514-PhysicalInorganicChemistryPage27of43• Unitactivity(whichmeansdilutionsolutionssoactivitiesapproximateconcentrations)• 1barpressureofanygaseouscomponent• Allsolidcomponentsareintheirstandardstates• T=298KThefreeenergyofthecell,DGocell=-nFEocellwhereFistheFaradayconstant=96,487Cmol-1nisthenumberofelectronstransferredinthereactionForacellreactiontobethermodynamicallyfavourableEocellmustbepositivesothatDGocellisnegative.IntheDaniellCell,Eocellat298K=1.10V(seefigureonpreviouspage).This1.10Viscomprisedof:+0.34VdrivingthereactionduetoreductionofCu2+and+0.76VdrivingthereactionduetooxidationofZn(s).Wheredothesevaluescomefrom?Firstly,DGocell=-nFEocell=-2*96,487*1.10=-212267Jpermolreaction=-212kJmol-1,whichdemonstratesthatthereactionfortheoxidationofthezincandthereductionofthecopperisspontaneous.AllEovaluesarerelatedonascaletothecellpotentialofthestandardhydrogenelectrode(SHE),whichisarbitrarilysetatavalueof0.0V(thinkofthisasanalogousto1HNMRwhereeveryotherresonanceisreportedrelativetoTMS).TheSHEconsistsofplatinumwirethatisconnectedtoaPtsurfaceincontactwithanaqueoussolutioncontaining1MH+inequilibriumwithH2gasatapressureof1atm.Thehalf-cellpotentialsareintensiveproperties,namelyindependentoftheamountofthereactingspecies.Allhalf-reactionsarewrittenasreductions(onlyreactantsareoxidizingagentsandonlyproductsarethereducingagents).ThemorepositivetheEovaluethemorereadilythereactionoccurs.Thehalf-cellthathasthemorepositiveEovalueactsasthecathode.BycombiningtheSHEwithanotherhalf-cell,e.g.,Cu2+aq/Cu(s)asintheDaniellcell,theEocanbedeterminedfromthemeasuredcellpotentialEocell.Thus,intheDaniellcell:WecannowseewhyZn(s)readilyreducesCu2+aqandprovidesthehugedrivingforcefortheDaniellcell.Zn(s)thusisthestrongerreducingagentandCu2+isthestrongeroxidizingagent.Let'slookatadifferentreaction.Let'sconsiderthewell-knowntitrationreactionofthereductionMnO4-withFe2+aqunderstandardconditions(1MH+,298K).Thehalfreactionsare:
4 2- + 4 H + 2 e MnO 2 + 2H 2 OE o = + 2.10V MnO 4 + e MnO 4 2- E o = + 0.90V 3 MnO 4 2- + 4 H MnO 2 + 2 MnO 4 + 2H 2 O 6 5 4 3 1 0 -1 -2 -3 201234567
n E o oxidation state Mn Mn 2+ Mn 3+ MnO 2 MnO 4 2- MnO 4 most stable state is Mn 2+ aq . (sits in energy minimum) -1.19 V +1.54 V +2.10 V +0.90 V +0.95 V 6 5 4 3 1 0 -1 -2 -3 2 0 1234567
n E o oxidation state MnMn(OH)
2 MnO 2 MnO 4 2- MnO 4 -4Mn(OH)
3 MnO 4 3- 6 5 4 3 1 0 -1 -2 -3 2 n E o Mn Mn 2+ Mn 3+ MnO 2 MnO 4 2- MnO 4 4 aq + 8 H aq + 5 e Mn 2+ aq + 4 H 2O (l)+ 1.51
E o / VG o / kJ mol -1 -728.5 MnO 4 aq + 4 H aq + 3 e MnO 2 (s) + 2 H 2O (l)+ 1.69
-489.2 O 2 + 2 Mn 2+ aq + 2 H 2 O 2 MnO 2 (s) + 4 H aq0.00MnO
4 aq + 4 H 2O + 5 e
Mn(OH)
2 (s) + 6 OH aq + 0.34-164MnO 2 (s) + 4 OH aq MnO 4 aq + 2 H 2O + 3 e
+ 0.59-170.8 M 2+ aq + 2 e M(s) E o O 2 + 2 Mn(OH) 2 (s)2 MnO 2 (s) + 2 H 2O+ 0.44-169.8
6 5 4 3 1 0 -1 -2 -3 2 0 1234567
n E o oxidation state -4 6 5 4 3 1 0 -1 -2 -3 2 n E o M Mn 2+ Mn 3+ MnO 2 MnO 4 2- MnO 4 Cr 2 O 7 2- Cr 3+ Cr 2+ V 2+ V 3+ VO 2+ VO 2 Fe 2+ Fe 3+ FeO 4 2- Co 2+ Co 3+ Ni 2+ Cu 2+ Cu Ti 2+ Ti 3+TiO 2+ M(s)M(g)atomization H
o a M(g)M 2+ (g) ionization (IP 1 + IP 2 units of o LFSE units of oChange in LFSE M
2+ ->M 3+ units of o M 3+ M 2+ M V -0.8-1.20.4 loss Cr -1.2-0.6 -0.6 gain M 2+ (g)M 2+ aq hydration H o hyd E o (M 2+ /M) / voltsIE / kJ mol
-1012345678
910number of d electrons for M 2+ -3 -2 -1 0 1 2 3 1750
2000
2250
2500
2750
3000
3250
3500
1500
IP 1 + IP 2 IP 3 E o (M 3+ /M 2+ ) / volts
IE / kJ mol
-1012345678
910number of d electrons for M 2+ -3 -2 -1 0 1 2 3quotesdbs_dbs22.pdfusesText_28
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