Nonlocal microplane model with strain-softening yield limits.pdf
The Activation Strain Model - University Of Illinois · The Activation Strain Model (ASM) • Also...
Transcript of The Activation Strain Model - University Of Illinois · The Activation Strain Model (ASM) • Also...
TheActivationStrainModel
DenmarkGroupMeetingAndrewZahrt
TheActivationStrainModel(ASM)• AlsoreferredtoasDistortionInteractionModel• TheActivationStrainModel:
– Afragmentbasedapproachwhichdecomposesthepotentialenergysurfaceintostrainandinteractionportionsinanefforttounderstandthephysicalpropertiesthatareresponsibleforenergybarriers.
– Leadstorationaldesignofefficientreactions• DevelopedindependentlybyHouk andBickelhaupt
Bickelhaupt etal.,Comput.Mol.Sci.,2015,5,324-343
BeforeUsingtheASM
• BeforeusingASM,first:1. Locatetransitionstateof
interest• ScanFromReactant
2. Performasteepestdescentcalculationtoobtaintheintrinsicreactioncoordinate(IRC)• ScanbacktoLocalMinima
oneachside
UsingtheASM
• ASMdecomposesenergyintotwoterms:o ΔE=ΔEstrain +ΔEinto ΔEstrain =geometricdeformationoffragments(reactants)fromareferencegeometry
o ΔEint =interactionbetweenfragments
o ThetransitionbarrieroccurswhentheslopeofΔEstrain =ΔEint
InterpretingtheActivationStrainDiagram(ASD)
• TwohypotheticalreactionsA(black)andB(blue).
• InteractionenergyisforreactionBismorestabilizingatanygivenpointalongthereactioncoordinate
• Singlepointanalysiswouldyieldoppositeconclusion!
Fernandez,I.;Bickelhaupt,F.M.Chem Soc Rev,2014,43,4953- 4967
UsingMolecularOrbitalTheorytoExplainΔEstrain
• ΔEstrain:MOtheorycanexplainwhystructuraldeformationdestabilizesachemicalspecies.– WalshDiagram
UsingEnergyDecompositionAnalysistoExplainΔEint
• EnergyDecompositionAnalysis:– AdaptedfromMorokuma,Ziegler,andRauk
ΔEint =ΔVelstat +ΔEPauli + ΔEoi (+ ΔEdisp)
– ΔVelstat =ElectrostaticPotentialEnergy• Usuallyattractive(negative)atchemicallyrelevantdistances
– ΔEPauli =PauliRepulsion:ResponsibleforStericRepulsion• Repulsive(positive)
– ΔEoi =OrbitalInteraction:Includeschargetransferandpolarization
• Stabilizing(negative)
– ΔEdisp =DispersionEnergy(arisingfrominducedinstantaneouspolarization)
• Repulsiveat<3.5Å,attractivebeyond3.5Å
Bickelhaupt etal.,Comput.Mol.Sci.,2015,5,324-343
Frontside vsBacksideSN2
• BimolecularNucleophilicSubstitution
Purpose:Toelucidateacausalrelationshipbetweenthereactants’electronicstructureandSN2reactivity
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
BacksideSN2:PES
Y=Cl;X=F,Cl, Br, I
F>Cl> Br> I
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
Frontside SN2:PES
Y=Cl;X=F,Cl, Br, I
F>Cl> Br> I
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
ApplyingASM
• ActivationStrainModeladdressesthefollowingquestions:
1. WhydoestheenergybarrierincreasewhenthenucleophileprogressesfromFtoI?
2. Whatphysicalpropertiesofthereactantsresultinbacksideattackbeingfavoredoverfrontside attack?
ApplyingASMtoAssessNucleophilicity
Y=Cl;X=F,Cl, Br, I
• Strainisconstantthroughoutallcases.
• TSlocationisdeterminedbytheslopeofΔEint
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
SN2:Nucleophilicity Trend
DominantorbitalinteractionisbetweenoccupiedAOonX– andCH3Y σ*C-Y
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
SN2:FactorsControllingΔEint
Y=Cl;X=F,Cl, Br, I 1. ΔEoi becomesmorenegativeduetoweakeningofC-Ybond
2. ΔVelstat becomesmorenegativebecauseofpositivechargebuilduponthecarbon.
SteeperDescentofΔEint=EarlierTransitionState=LowerEnergyBarrier
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
ActivationStrainAnalysisforFrontside vsBacksideAttack
Y=Cl;X=F,Cl, Br, IY=Cl;X=F,Cl, Br, I
Bento,A.P.;Bickelhaupt,F.M.J.Org.Chem.2008,73,7290-7299
SummaryofSN2
1. OrbitalInteractiontermdictatesnucleophilicity– EnhancesstabilizationfromΔVelstat
2. Frontside attackisdisfavoredbecausePaulirepulsionmakestheslopeofEint lesssteep
CaseI:OxidativeAddition
• DirectOxidativeInsertion
• SN2TypeMechanism
Goal:Todeterminehowcatalystactivitydependsonelectronic
structureBickelhaupt,F.M.;J.Comput.Chem. 1999,20,114–128
Pd(0)CatalyzedBondActivationThroughOxidativeInsertion
ΔEǂ /Ea (kcal/mol)
-21.7/2.7
-1.6/6.4
-0.7/7.5
-4.3/9.6
12.6 /21.2
ΔEstrain/Eint (kcal/mol)
55.6 /-77.3
53.5 /-55.1
54.7 /-55.4
8.8 /-13.1
39.4 /-26.8
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
StrainandC-(H/C/Cl)BondStretch
ΔEstrain=55.6kcal/mol ΔEstrain=53.5 kcal/mol ΔEstrain=54.7 kcal/mol
ΔEstrain=8.8 kcal/molΔEstrain=39.4 kcal/mol
H-H:1.38ÅStretch:97%
C-H:1.61ÅStretch:47%
C-H:1.63ÅStretch:48%
C-C:1.93ÅStretch:26%
C-Cl:1.97ÅStretch:9%
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
StrainandC-(H/C/Cl)BondStretch
-30
-20
-10
0
10
20
30
40
50
60
0 0.2 0.4 0.6 0.8 1
kcal/m
ol
%Stretch
StrainEnergyVs%Stretch
Energyvs%Stretch
ΔEstrain correlateswith%stretch,butΔEǂ doesnot!
ΔEint mustbemorethoroughlyinvestigatedtounderstandreactionbarrier.Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
EnergyDecompositionAnalysis
ΔEint =ΔVelstat +ΔEPauli + ΔEoi (Allinkcal/mol)
ΔVelstat =-183.7ΔEPauli =208.7
ΔVelstat =-170.4ΔEPauli =211.1
ΔVelstat =-171.9ΔEPauli =209.8
ΔVelstat =-139.5ΔEPauli =192.6
ΔVelstat =-76.7ΔEPauli =112.3
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
AnalysisofΔEoi
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
InsertionintoH-H
Orbitalσ*H-H 4dσH-H5s
Eorbital(eV)-2.854-4.193-8.438-3.423
Overlap0.3000.566
Population(e–) 0.439.281.730.45
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
Eoi =-102.3kcal/mol
InsertionintoC-H
Orbitalσ*C-H 4dσC-H5s
Eorbital(eV)-1.625-4.193-7.435 -3.423
Overlap0.3270.401
Population(e–) 0.369.321.710.38
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
Eoi =-95.8kcal/mol
InsertionintoC-C
Orbitalσ*C-C 4dσC-C5s
Eorbital(eV)-0.391-4.193-7.303-3.423
Overlap0.1360.213
Population(e–) 0.259.421.830.22
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
Eoi =-79.9kcal/mol
InsertionintoC-Cl
Orbitalσ*C-Cl 4dσC-C5s
Eorbital(eV)-2.066-4.193-7.142-3.423
Overlap0.0820.144
Population(e–) 0.199.591.910.18
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
Eoi =-48.7kcal/mol
SummaryofPd(0)CatalyzedBondActivation
ΔEǂ / ΔEstrain /Eint(kcal/mol)
-21.7/55.6 /-77.3
-1.6/53.5 /-55.1
-4.3/8.8 /-13.1
12.6 /39.4 /-26.8
ΔEPauli + ΔEelstat /Eoi(kcal/mol)
25 /-102.3
40.7 /-95.8
35.6 /-48.7
53.5 /-93.3
Diefenbach,A.;Bickelhaupt,F.M.J.Phys.Chem.A.2004,108,8460-8446
AnionAssistance
ΔEǂ / ΔEstrain /Eint(kcal/mol)
-21.7/55.6 /-77.3
-35.3/56.1 /-91.4
Ox.Ins.-4.3/8.8 /-13.1SN224.5/ 87.5 / -63.2
Ox.Ins.-10.3/9.6 /-19.9SN2-18.5/ 91.8 / -110.3
Diefenbach,A.;deJong,GT,Bickeclhaupt,FM.J.Chem.TheoryComput.,2005,1,286–298
H-HBondInsertion
ΔEǂ / ΔEstrain /Eint(kcal/mol)
-21.7/55.6 /-77.3
-35.3/56.1 /-91.4
(ΔEPauli / ΔEelstat)ΔEPauli + ΔEelstat /Eoi
(kcal/mol)
(208.7/-183.7)25 /-102.3
(176.3/-173.6)2.7 /-94.1
PopulationAnalysis:σH-H =1.73σ*H-H =0.43Pd (4d)=9.28Pd (5s)=0.45
PopulationAnalysis:σH-H =1.89σ*H-H =0.57Pd (4d)=9.32Pd (5s)=0.21
Diefenbach,A.;deJong,GT,Bickeclhaupt,FM.J.Chem.TheoryComput.,2005,1,286–298
Pd-Hdistancedecreasesfrom1.54to1.61
H-HBondInsertion
Diefenbach,A.;deJong,GT,Bickeclhaupt,FM.J.Chem.TheoryComput.,2005,1,286–298
ReactivitywithC-Xbond
ΔEǂ / ΔEstrain /Eint(kcal/mol)
ΔEPauli + ΔEelstat /Eoi(kcal/mol)
Ox.Ins.-4.3/8.8 /-13.1SN224.5/ 87.5 / -63.2
35.6/-48.738.3/-101.4
Diefenbach,A.;deJong,GT,Bickeclhaupt,FM.J.Chem.TheoryComput.,2005,1,286–298
ReactivitywithC-Xbond
ΔEǂ / ΔEstrain /Eint(kcal/mol)
ΔEPauli + ΔEelstat /Eoi(kcal/mol)
22.4/-42.344.5/-154.7
Ox.Ins.-10.3/9.6 /-19.9SN2-18.5/ 91.8 / -110.3
ElongationofC-ClbondinTSlowersLUMOenergyby4.6eV.
Resultsinbetter4d– σ*orbitaloverlap.
SummaryofOxidativeAddition
• TheinterplaybetweenStrainandInteractionDictateReactionbarriers:– H-Hhashigheststrainenergy,butlowestactivationenergywhileC-Clhassecondlowestbarrierwithlowestinteractionenergy
• AnionassistancesteepensΔEint curve,resultinginanearliertransitionstateandalowerenergybarrier.
Intermission
CaseIIa:ExoSelectiveDielsAlder
Gouverneur,V;Houk,K.etal.JACS,2009 ,131, 947–195
ExovsEndoSelectivity
Gouverneur,V;Houk,K.etal.JACS,2009 ,131, 947–195
Distortion– InteractionAnalysis
Thereactantsintheendopathwayaremoredistortedthantheexo pathway,resultinginexo
selectivity.
Gouverneur,V;Houk,K.etal.JACS,2009 ,131, 947–195
StraininTransitionState
Higherdistortioninendo pathwayisduetoamoreasynchronousTS
Gouverneur,V;Houk,K.etal.JACS,2009 ,131, 947–195
SummaryofExoSelectiveDielsAlder
Distortion/Interactionanalysisleadstoa
straightforwardmodeltoexplainselectivity
Gouverneur,V;Houk,K.etal.JACS,2009 ,131, 947–195
CaseIIb:MO4 Cylcoaddition toEthylene
• 3+2vs2+2• Itwasknownthat3+2wastheoperativepathway• ItwasalsoknowsthatAminebasescatalyzedthereaction• Distortion/InteractionAnalysisandEnergyDecomposition
Analysisemployedtoexplain:– Themechanismofaminebasecatalysis– Reactivitydifferencesbetweenselectedmetals
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
32TSvs22TS(OsO4)
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
32TSvs22TS(OsO4):uncatalyzed
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
• OOsO bondanglesequallydistorted
• Os-Obondin22TSmoredistorted
• 22TSlaterthan32TS
32TSvs22TS(OsO4):catalyzed
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
• 32TSislessdistortedthaninuncatalyzedcase
• 22TSmoredistortedthanuncatalyzed case
DistortionInteractionAnalysis:32TSUncatalyzed Case
• OsO4 remainsapprox5kcal/mol distortedthanethylenethroughouttheentiresurface
DistortionInteractionAnalysis:Uncatalyzed Case
• PositiveInteractionEnergy!
CurrentAnalysis• AnsweredQuestions:
Q:Whyisthe3+2TSpreferredoverthe2+2TS?A:The3+2pathwayhasanearlier,lessdistortedTS.
Q:Whydoesthepresenceofanamineligandcatalyzethereaction?A:TheamineNH3OsO4 complexisdistortedlessintheTS,resultinginalowerenergybarrier
• UnansweredQuestions:– Howdoweinterpretpositiveinteractionenergy?– CanthereactivityofOsmiumbeunderstoodintermsofits
electronicstructure?• Cansimilaranalysisexplainthereactivityofothermetals?
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
AbsolutelyLocalizedMolecularOrbitalInteractionDecompositionAnalysis
• ALMO-EDA:ΔEint =ΔEFRZ+ΔEPOL + ΔECT + ΔEHO
– ΔEFRZ:FrozenElectronDensities:IncludesCoulombicinteractionandexchange/correlation.
– ΔEPOL:Polarization– ΔECT:ChargeTransfer– ΔEHO:Higherorderorbitalrelaxationeffects(includesallinductioneffects)
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
Positive interaction energy
ComparisonAcrossMetals:Distortion,InteractionandEnergyBarrier
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
EDAatNonstationaryPoints
Ess,D. J.Org.Chem.,2009 ,74,1498-1508
Distortion/InteractionCurve
MO4 Cylcoaddition toEthylene:Summary
• ChargetransferfromethylenetoOsO4 ismostefficientbecauselow-lyingLUMOofOsO4
• MnO4– isanactiveoxidantbecauseofitsearlyTS
– Lowstrain
• TcO4– andReO4
– arelessactivebecauseoftheirlaterTS.– ΔEint developsmoreslowlyduetolessstabilizationfromchargetransfer
Summary
• ASMorDistortion/Interactionanalysiscanbeusedinavarietyofwaystoshowthephysicaloriginofenergybarriers– FrequentlyusedwithEDA
• ThePEScanbedecomposedinmultipledifferentways:– Methodofdecompositionisatthediscretionofthepractitioner