Mechanistic study of the rhodium-catalyzed carboxylation of simple aromatic compounds with carbon dioxide

Article abstract of DOI:10.1039/C6SC03838G

A detailed mechanism of the Rh(i)-catalyzed carboxylation of simple aromatic compounds via C-H bond activation was investigated. Kinetic studies with model compounds of the postulated key intermediates revealed that 14-electron complexes, RhMe(dcype) and RhPh(dcype), participated in the C-H bond activation step and the carboxylation step, respectively. Interestingly, the undesired carboxylation of RhMe(dcype) to give acetic acid was found to be much faster than the desired C-H bond activation reaction under stoichiometric conditions, however, the C-H bond activation reaction could occur under catalytic conditions. Careful controlled experiments revealed that C-H bond activation using RhMe(dcype) became competitive with its direct carboxylation under the condition that the concentration of CO₂ in the liquid phase was rather low. This factor could be controlled to some extent by mechanical factors such as the stirring rate and the shape of the reaction vessel. The resting state of the rhodium species under catalytic conditions was found to be [RhCl(dcype)]₂, and the proposed intermediates such as RhMe(dcype) and Rh(OBz)(dcype) were readily converted to the most stable state, [RhCl(dcype)]₂, via transmetallation with [Al]-Cl species, thus preventing the decomposition of the active catalytic species.

Full text of DOI:10.1039/C6SC03838G

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Page 1 of 8
Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
View Article Online
DOI: 10.1039/C6SC03838G
JournalꢀNameꢀ
ꢀ
ARTICLEꢀ
MechanisticꢀStudyꢀofꢀRhodium-CatalyzedꢀCarboxylationꢀofꢀSimpleꢀ
AromaticꢀCompoundsꢀwithꢀCarbonꢀDioxideꢀ
Receivedꢀ00thꢀJanuaryꢀ20xx,ꢀ
Acceptedꢀ00thꢀJanuaryꢀ20xxꢀ
TakuyaꢀSuga,ꢀTakanobuꢀSaitou,ꢀJunꢀTakayaꢀandꢀNobuharuꢀIwasawa*ꢀ
DOI:ꢀ10.1039/x0xx00000xꢀ
Theꢀ detailedꢀ mechanismꢀ ofꢀ Rh(I)-catalyzedꢀ carboxylationꢀ ofꢀ simpleꢀ aromaticꢀ compoundsꢀ viaꢀ C–Hꢀ bondꢀ activationꢀ wasꢀ
investigated.ꢀ Kineticꢀ studiesꢀ withꢀ modelꢀ compoundsꢀ ofꢀ theꢀ postulatedꢀ keyꢀ intermediatesꢀ revealedꢀ thatꢀ 14-electronꢀ
complexesꢀ RhMe(dcype)ꢀ andꢀ RhPh(dcype)ꢀ participatedꢀ inꢀ theꢀ C–Hꢀ bondꢀ activationꢀ stepꢀ andꢀ theꢀ carboxylationꢀ step,ꢀ
respectively.ꢀInterestingly,ꢀundesiredꢀcarboxylationꢀofꢀRhMe(dcype)ꢀtoꢀgiveꢀaceticꢀacidꢀwasꢀfoundꢀtoꢀbeꢀmuchꢀfasterꢀthanꢀ
theꢀ desiredꢀ C–Hꢀ bondꢀ activationꢀ reactionꢀ underꢀ theꢀ stoichiometricꢀ conditions,ꢀ however,ꢀ C–Hꢀ bondꢀ activationꢀ reactionꢀ
couldꢀ occurꢀ underꢀ theꢀ catalyticꢀ conditions.ꢀ Carefulꢀ controllingꢀ experimentsꢀ revealedꢀ thatꢀ C–Hꢀ bondꢀ activationꢀ byꢀ theꢀ
www.rsc.org/ꢀ
2
RhMe(dcype)ꢀbecameꢀcompetitiveꢀwithꢀitsꢀdirectꢀcarboxylationꢀunderꢀtheꢀconditionsꢀthatꢀtheꢀconcentrationꢀofꢀCO ꢀinꢀtheꢀ
liquidꢀphaseꢀwasꢀratherꢀlow.ꢀThisꢀfactorꢀcouldꢀbeꢀcontrolledꢀtoꢀsomeꢀextentꢀbyꢀmechanicalꢀfactorsꢀsuchꢀasꢀtheꢀstirringꢀrateꢀ
andꢀtheꢀshapeꢀofꢀtheꢀreactionꢀvessel.ꢀTheꢀrestingꢀstateꢀofꢀtheꢀrhodiumꢀspeciesꢀunderꢀcatalyticꢀconditionsꢀwasꢀfoundꢀtoꢀbeꢀ
[
2
RhCl(dcype)] ,ꢀandꢀtheꢀproposedꢀintermediatesꢀsuchꢀasꢀRhMe(dcype)ꢀandꢀRh(OAc)(dcype)ꢀwereꢀreadilyꢀconvertedꢀtoꢀtheꢀ
mostꢀ stableꢀ [RhCl(dcype)]
catalyticꢀspecies.ꢀ
2
ꢀ viaꢀ transmetallationꢀ withꢀ [Al]–Clꢀ species,ꢀ thusꢀ preventingꢀ theꢀ decompositionꢀ ofꢀ theꢀ activeꢀ
5
x 10-3 mmol [RhCl(dcype)]2
1
1
1
.1 mmol AlMe1.5(OEt)1.5
atm CO2
Introductionꢀ
H+
carboxylic
acids
Catalyticꢀ directꢀ carboxylationꢀ ofꢀ simpleꢀ hydrocarbonsꢀ withꢀ arenes
carbonꢀ dioxideꢀ (CO2)ꢀ isꢀ aꢀ formidableꢀ challengeꢀ inꢀ organicꢀ
1
chemistry. ꢀ Recently,ꢀ weꢀ reportedꢀ Rh(I)-catalyzedꢀ
DMA (0.1 mL), TMU (6 µL)
8
5 – 145 ºC, 6 h, closed
2 mL
carboxylationꢀofꢀsimpleꢀaromaticꢀcompoundsꢀsuchꢀasꢀbenzeneꢀ
andꢀtolueneꢀbyꢀusingꢀaꢀcombinationꢀofꢀ[RhCl(dcype)]2ꢀ1ꢀ(dcype:ꢀ
CO Me
CO
Me
2
2
R
Fe
1
,2-bis(dicyclohexylphosphino)ethane)ꢀandꢀAlMe1.5(OEt)1.5ꢀasꢀaꢀ
N
CO H
2
2-4
stoichiometricꢀ methylatingꢀ agentꢀ (Schemeꢀ 1). ꢀ Theꢀ mostꢀ
attractiveꢀ featureꢀ ofꢀ thisꢀ reactionꢀ isꢀ itsꢀ wideꢀ generality.ꢀ Notꢀ
onlyꢀelectronꢀpoor/richꢀarenes,ꢀbutꢀalsoꢀheteroaromaticsꢀsuchꢀ
asꢀ benzofuranꢀ andꢀ indoleꢀ wereꢀ carboxylatedꢀ successfully.ꢀ
Furthermore,ꢀ ferroceneꢀ showedꢀ remarkableꢀ reactivityꢀ inꢀ thisꢀ
reaction.ꢀ
21a
60a,b
TON R =
H
37
44
15
CF3
aIsolated after Me esterification.
b5 mmol ferrocene in cyclooctane.
OMe
ꢀ
Schemeꢀ1ꢀꢀRh-catalyzedꢀC–Hꢀbondꢀcarboxylation.ꢀꢀ
AlMe1.5(OEt)1.5.ꢀ
TheꢀproposedꢀreactionꢀmechanismꢀisꢀshownꢀinꢀSchemeꢀ2.ꢀTheꢀ
reactionꢀ startsꢀ withꢀ generationꢀ ofꢀ aꢀ 14-electronꢀ
methylrhodium(I)ꢀ complexꢀ Aꢀ byꢀ transmetallationꢀ ofꢀ
Theꢀkeyꢀofꢀourꢀsuccessꢀconsistsꢀofꢀthreeꢀmainꢀfactors.ꢀTheꢀfirstꢀ
oneꢀ isꢀ theꢀ choiceꢀ ofꢀ methylrhodium(I)ꢀ asꢀ theꢀ C–Hꢀ activationꢀ
species.ꢀ Itꢀ wasꢀ reportedꢀ asꢀ aꢀ stoichiometricꢀ reactionꢀ byꢀ
Andersen’sꢀandꢀField’sꢀgroupsꢀthatꢀheatingꢀorꢀphotoirradiatingꢀ
methylrhodium(I)ꢀ speciesꢀ inꢀ benzeneꢀ affordedꢀ correspondingꢀ
[
RhCl(dcype)]2ꢀ 1ꢀ withꢀ AlMe1.5(OEt)1.5ꢀ followedꢀ byꢀ oxidativeꢀ
2
additionꢀ ofꢀ anꢀ sp ꢀ C–Hꢀ bondꢀ ofꢀ benzeneꢀ toꢀ A,ꢀ givingꢀ
phenyl(hydrido)(methyl)rhodium(III)ꢀintermediateꢀB.ꢀReductiveꢀ
eliminationꢀofꢀmethaneꢀfromꢀBꢀaffordsꢀaꢀreactiveꢀ14-electronꢀ
5
5
phenylrhodium(I)ꢀ species. ꢀ Itꢀ wasꢀ expectedꢀ thatꢀ byꢀ usingꢀ
phenylrhodium(I)ꢀcomplexꢀC. ꢀNucleophilicꢀadditionꢀofꢀCꢀtoꢀCO2ꢀ
6
givesꢀaꢀrhodium(I)ꢀbenzoateꢀcomplexꢀD, ꢀwhichꢀisꢀconvertedꢀtoꢀ
methylrhodium(I)ꢀ species,ꢀ theꢀ irreversibleꢀ dissociationꢀ ofꢀ
methaneꢀ fromꢀ intermediateꢀ Bꢀ wouldꢀ giveꢀ theꢀ desiredꢀ
arylrhodium(I)ꢀ speciesꢀ efficiently.ꢀ Theꢀ secondꢀ oneꢀ isꢀ theꢀ
reactivityꢀ ofꢀ RhMe(dcype)ꢀ A.ꢀ Forꢀ theꢀ successꢀ ofꢀ theꢀ
preparationꢀ ofꢀ benzoicꢀ acid,ꢀ directꢀ carboxylationꢀ ofꢀ Aꢀ toꢀ
produceꢀ aceticꢀ acidꢀ shouldꢀ beꢀ slowerꢀ thanꢀ theꢀ C–Hꢀ bondꢀ
activationꢀ ofꢀ benzeneꢀ byꢀ A.ꢀ Ifꢀ theꢀ directꢀ carboxylationꢀ wasꢀ
muchꢀfasterꢀthanꢀtheꢀC–Hꢀbondꢀactivation,ꢀtheꢀreactionꢀwouldꢀ
methylrhodium(I)ꢀAꢀthroughꢀtransmetallationꢀwithꢀꢀꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ1ꢀꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
Page 2 of 8
ARTICLEꢀ
JournalꢀNameꢀ
Me
P
P
mechanismꢀ ofꢀ thisꢀ rhodium-catalyzedꢀ C–Hꢀ carboxylelationꢀ
DOI: 10.1039/C6SC03838G
1
View Artic Online
Al–Me
Rh
H
reactionꢀ basedꢀ onꢀ kineticꢀ studiesꢀ usingꢀ severalꢀ modelꢀ
compounds,ꢀ examinationꢀ ofꢀ variousꢀ reactionꢀ conditionsꢀ
includingꢀtheꢀshapeꢀofꢀtheꢀreactionꢀvesselsꢀandꢀtheꢀstirringꢀrate,ꢀ
analysisꢀ ofꢀ theꢀ reactionꢀ mixture,ꢀ andꢀ someꢀ controllingꢀ
experiments.ꢀ
Ph–H
– Me–H
–
Al–Cl
Ph
B
P
Me
P
P
Ph
Rh
Rh
P
A
C
CO2
Al–Me
P
P
O
–
Al–O CPh
Ph
Resultsꢀandꢀdiscussionꢀ
2
Rh
O
D
1:ꢀPreparationꢀandꢀreactivityꢀofꢀtetracoordinatedꢀ16-electronꢀ
rhodiumꢀspeciesꢀ
ꢀ
Schemeꢀ2ꢀꢀPostulatedꢀreactionꢀmechanism.ꢀ
Toꢀ supportꢀ theꢀ proposedꢀ reactionꢀ mechanismꢀ shownꢀ inꢀ
Schemeꢀ 2,ꢀ weꢀ initiallyꢀ triedꢀ toꢀ prepareꢀ eachꢀ intermediateꢀ inꢀ
theꢀ proposedꢀ catalyticꢀ cycle.ꢀ Inꢀ particular,ꢀ 14-electronꢀ
complexesꢀRhMe(dcype)ꢀAꢀandꢀRhPh(dcype)ꢀCꢀwereꢀtheꢀmostꢀ
attractiveꢀ becauseꢀ theyꢀ wereꢀ thoughtꢀ toꢀ beꢀ theꢀ trueꢀ
intermediatesꢀinꢀtheꢀmostꢀimportantꢀC–Hꢀbondꢀactivationꢀandꢀ
carboxylationꢀsteps.ꢀꢀ
produceꢀ aceticꢀ acidꢀ only.ꢀ Theꢀ thirdꢀ oneꢀ isꢀ theꢀ choiceꢀ ofꢀ theꢀ
methylatingꢀ agentꢀ toꢀ regenerateꢀ A.ꢀ Methylaluminumꢀ wasꢀ
selectedꢀ becauseꢀ itꢀ isꢀ well-knownꢀ toꢀ beꢀ reactiveꢀ forꢀ
transmetallation,ꢀbutꢀitꢀdoesꢀnotꢀdirectlyꢀreactꢀwithꢀCO2ꢀunderꢀ
appropriateꢀ conditions.ꢀ Otherꢀ reagentsꢀ suchꢀ asꢀ MeMgBrꢀ areꢀ
unsuitableꢀforꢀthisꢀreason.ꢀ
Tricoordinatedꢀ14-electronꢀalkylrhodiumꢀcomplexesꢀareꢀknownꢀ
toꢀbeꢀsoꢀunstableꢀthatꢀtheyꢀhadꢀnotꢀbeenꢀisolatedꢀexceptꢀforꢀ
Apartꢀfromꢀtheꢀsyntheticꢀutility,ꢀtheꢀnoteworthyꢀfeatureꢀofꢀthisꢀ
reactionꢀisꢀtheꢀrealizationꢀofꢀC–Hꢀbondꢀactivationꢀfollowedꢀbyꢀ
nucleophilicꢀ additionꢀ byꢀ usingꢀ aꢀ combinationꢀ ofꢀ aꢀ low-valentꢀ
transitionꢀmetalꢀcatalystꢀandꢀaꢀstoichiometricꢀalkylatingꢀagent.ꢀ
Suchꢀ C–Hꢀ bondꢀ functionalizationꢀ strategiesꢀ areꢀ quiteꢀ limitedꢀ
andꢀmostꢀofꢀtheꢀreportedꢀC-Hꢀactivation–nucleophilicꢀadditionꢀ
reactionsꢀ utilizeꢀ high-valentꢀ transitionꢀ metalꢀ complexesꢀ suchꢀ
13
fewꢀ specificꢀ examples. ꢀ Indeed,ꢀ weꢀ initiallyꢀ attemptedꢀ toꢀ
prepareꢀ themꢀ byꢀ treatmentꢀ ofꢀ [RhCl(dcype)]2ꢀ 1ꢀ withꢀ severalꢀ
methylatingꢀagentsꢀsuchꢀasꢀmethyllithium,ꢀmethylmagnesiumꢀ
bromideꢀ andꢀ trimethylaluminum,ꢀ however,ꢀ allꢀ effortsꢀ turnedꢀ
outꢀ toꢀ beꢀ fruitless.ꢀ Therefore,ꢀ weꢀ decidedꢀ toꢀ prepareꢀ
7
tetracoordinatedꢀ16-electronꢀcomplexesꢀRhMe(PCy )(dcype)ꢀ2ꢀ
3
asꢀ Rh(III)ꢀ forꢀ C-Hꢀ bondꢀ activation. ꢀ Inꢀ 2010,ꢀ weꢀ reportedꢀ theꢀ
firstꢀ exampleꢀ ofꢀ suchꢀ reaction,ꢀ thatꢀ is,ꢀ rhodium-catalyzedꢀ
andꢀ RhPh(PCy3)(dcype)ꢀ 3ꢀ asꢀ appropriateꢀ precursorsꢀ ofꢀ 14-
14
8
directꢀ carboxylationꢀ ofꢀ 2-phenylpyridines. ꢀ Inꢀ 2012,ꢀ Yoshikaiꢀ
electronꢀcomplexꢀ(Schemeꢀ3). ꢀ2ꢀandꢀ3ꢀwereꢀpreparedꢀinꢀgoodꢀ
yieldsꢀ byꢀ treatmentꢀ ofꢀ [RhCl(dcype)]2ꢀ withꢀ MeLiꢀ andꢀ PhLi,ꢀ
respectivelyꢀ inꢀ theꢀ presenceꢀ ofꢀ aꢀ stoichiometricꢀ amountꢀ ofꢀ
reportedꢀ aꢀ catalyticꢀ C–Hꢀ bondꢀ activationꢀ ofꢀ 2-phenylpyridineꢀ
derivativesꢀ usingꢀ aꢀ combinationꢀ ofꢀ aꢀ cobaltꢀ catalystꢀ andꢀ
stoichiometricꢀ organomagnesiumꢀ reagent,ꢀ followedꢀ byꢀ
1
5
1
31
PCy3. ꢀTheirꢀstructuresꢀwereꢀdeterminedꢀbyꢀ Hꢀandꢀ PꢀNMR.ꢀ3ꢀ
wasꢀalsoꢀcharacterizedꢀbyꢀsingleꢀcrystalꢀX-rayꢀstructureꢀanalysisꢀ
9
nucleophilicꢀ additionꢀ toꢀ N-arylimines. ꢀ Veryꢀ recently,ꢀ Wangꢀ
reportedꢀtheꢀuseꢀofꢀaꢀmanganeseꢀcatalystꢀwithꢀaꢀstoichiometricꢀ
amountꢀ ofꢀ dimethylzincꢀ wasꢀ effectiveꢀ toꢀ theꢀ couplingꢀ ofꢀ 2-
ꢀ
(
seeꢀSI).ꢀ
Next,ꢀ theꢀ reactivityꢀ ofꢀ theseꢀ complexesꢀ forꢀ C–Hꢀ bondꢀ
activationꢀ andꢀ carboxylationꢀ reactionꢀ wasꢀ examined.ꢀ Toꢀ ourꢀ
delight,ꢀRhMe(PCy3)(dcype)ꢀ2ꢀwasꢀfoundꢀtoꢀreactꢀwithꢀbenzeneꢀ
toꢀgiveꢀRhPh(PCy3)(dcype)ꢀ3ꢀunderꢀargonꢀatꢀ85ꢀºCꢀwithꢀperfectꢀ
conversionꢀalthoughꢀpartialꢀdecompositionꢀwasꢀalsoꢀobservedꢀ
10,11
phenylpyridinesꢀ withꢀ aldehydesꢀ andꢀ nitriles.
ꢀ Thisꢀ kindꢀ ofꢀ
catalyticꢀ nucleophilicꢀ additionꢀ isꢀ stillꢀ limited,ꢀ butꢀ wouldꢀ
becomeꢀ aꢀ powerfulꢀ methodologyꢀ inꢀ C–Hꢀ bondꢀ
functionalizationꢀreactions.ꢀ
(Schemeꢀ4).ꢀMoreover,ꢀfurtherꢀexposureꢀofꢀthisꢀsolutionꢀtoꢀ1ꢀ
atmꢀ CO2ꢀ atꢀ 85ꢀ ºCꢀ gaveꢀ aꢀ mixtureꢀ ofꢀ carboxylatedꢀ productsꢀ
Rh(O2CPh)(dcype)ꢀ Dꢀ andꢀ Rh(O2CPh)(PCy3)(dcype)ꢀ D’ꢀ (Dꢀ :ꢀ D’ꢀ =ꢀ
Asꢀ describedꢀ above,ꢀ severalꢀ reactionsꢀ haveꢀ recentlyꢀ beenꢀ
reportedꢀforꢀthisꢀtypeꢀofꢀC-Hꢀactivation–nucleophilicꢀadditionꢀ
reactions,ꢀhowever,ꢀthereꢀhasꢀbeenꢀalmostꢀnoꢀdetailedꢀstudyꢀ
onꢀtheꢀmechanismꢀofꢀsuchꢀreactions,ꢀprobablyꢀbecauseꢀofꢀtheꢀ
difficultyꢀ inꢀ capturingꢀ highlyꢀ reactiveꢀ alkylꢀ orꢀ arylꢀ transitionꢀ
metalꢀ intermediates.ꢀ Forꢀ example,ꢀ confirmationꢀ ofꢀ theꢀ
intermediacyꢀ ofꢀ 14-electronꢀ complexꢀ inꢀ C–Hꢀ activationꢀ andꢀ
carboxylationꢀ stepꢀ isꢀ notꢀ necessarilyꢀ easyꢀ inꢀ ourꢀ reactionꢀ
becauseꢀ ofꢀ theirꢀ instability.ꢀ Asꢀ alreadyꢀ described,ꢀ
stoichiometricꢀreactivityꢀofꢀrelevantꢀmethylrhodium(I)ꢀspeciesꢀ
toꢀC–Hꢀbondꢀactivationꢀhasꢀbeenꢀknownꢀforꢀmoreꢀthanꢀthreeꢀ
decades,ꢀ butꢀ itsꢀ detailedꢀ mechanisticꢀ studyꢀ hasꢀ notꢀ beenꢀ
1
inꢀ theseꢀ twoꢀ reactions.ꢀ Theꢀ rhodiumꢀ benzoatesꢀ wereꢀ
ꢀ:ꢀ2ꢀatꢀroomꢀtemperature).ꢀNoꢀintermediatesꢀwereꢀobservedꢀ
31
characterizedꢀbyꢀcomparingꢀtheirꢀ PꢀNMRꢀspectraꢀwithꢀthoseꢀ
ofꢀ authenticꢀ samplesꢀ Dꢀ andꢀ D’ꢀ (seeꢀ SIꢀ forꢀ theirꢀ preparativeꢀ
methods).ꢀ
ꢀ
Cy2
P
1 equiv. PCy3
1 equiv. MeLi or PhLi
Cy2
P
Cl
R
Rh
Rh
5
2
THF
PCy3
carriedꢀ out. ꢀ Concerningꢀ theꢀ carboxylationꢀ step,ꢀ thereꢀ areꢀ
P
P
Cy2
Cy2
2 (R = Me) : 57 %
(R = Ph) : 44 %
severalꢀ reportsꢀ forꢀ stoichiometricꢀ carboxylationꢀ reactionsꢀ ofꢀ
ꢀ
arylrhodium(I)ꢀ complexes, ꢀ however,ꢀ theirꢀ mechanismsꢀ haveꢀ
6
1
3
12ꢀ
ꢀ
ꢀ
beenꢀ proposedꢀ onlyꢀ byꢀ theoreticalꢀ studies. Furthermore,ꢀ
transmetallationꢀbehaviorsꢀandꢀtheꢀrestingꢀstateꢀareꢀalsoꢀleftꢀ
unclarified.ꢀ Inꢀ thisꢀ paper,ꢀ weꢀ reportꢀ detailedꢀ analysisꢀ ofꢀ theꢀ
Schemeꢀ3ꢀꢀPreparationꢀofꢀmodelꢀcomplexes.ꢀ
2
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Page 3 of 8
Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
JournalꢀNameꢀ
ꢀARTICLEꢀ
Cy2
P
Cy
P
2
– ln ! ! ! = !! ! PCy! –!
!
1
View Article Online
DOI: 10.1039/C6SC03838G
Me
Ph
benzene
Rh
Rh
(
+ byproducts)
PCy3
P
Cy
PCy
3
!! = 6.9 × 10!! M ∙ min!!
!! = 1.0 × 10!! [M ∙ min!!
!! !! = 6.9
P
Cy2
8
3
5 ºC
0 min
2
2
3
]
then
atm CO2
Cy2
P
Cy2
P
1
O
O
O CPh
2
Rh
Ph
+
Rh
Theꢀvalueꢀofꢀ–ln([2]/[2]0)ꢀwasꢀcompletelyꢀproportionalꢀtoꢀtheꢀ
8
3
5 ºC
0 min
PCy3
P
Cy2
P
Cy
2
reactionꢀ timeꢀ evenꢀ afterꢀ 90ꢀ %ꢀ conversion,ꢀ andꢀ wasꢀ inverselyꢀ
–4
proportionalꢀ toꢀ [PCy3]ꢀ withꢀ theꢀ rateꢀ constantꢀ kHꢀ =ꢀ 6.9ꢀ xꢀ 10 ꢀ
–1
M·min ]ꢀatꢀ75ꢀºC.ꢀAccordingꢀtoꢀsteadyꢀstateꢀapproximation,ꢀ
D
D'
ꢀ
[
thisꢀ reactionꢀ includesꢀ dissociationꢀ ofꢀ PCy3ꢀ beforeꢀ theꢀ rate-
aꢀ
Schemeꢀ4ꢀꢀReactionsꢀofꢀmodelꢀcomplexes.
determiningꢀstep.ꢀInꢀaddition,ꢀtheꢀreactionꢀinꢀbenzene-d6ꢀwasꢀ
–1
–
4
2
.ꢀMechanisticꢀstudyꢀonꢀC–Hꢀbondꢀactivationꢀbyꢀmethylrhodium(I)ꢀ apparentlyꢀslowerꢀ(kDꢀ=ꢀ1.0ꢀxꢀ10 ꢀ[M·min ])ꢀthanꢀinꢀbenzene-
speciesꢀ
d0ꢀandꢀtheꢀKIEꢀvalueꢀ(kH/kD)ꢀwasꢀestimatedꢀtoꢀbeꢀ6.9.ꢀThisꢀlargeꢀ
KIEꢀ valueꢀ stronglyꢀ suggestsꢀ C–Hꢀ bondꢀ activationꢀ stepꢀ isꢀ rate-
determiningꢀinꢀthisꢀstoichiometricꢀreaction.ꢀ
Withꢀ theꢀ suitableꢀ modelꢀ complexesꢀ inꢀ hand,ꢀ weꢀ carriedꢀ outꢀ
kineticꢀ studyꢀ ofꢀ theꢀ C–Hꢀ bondꢀ activationꢀ stepꢀ byꢀ monitoringꢀ
1
ꢀ
Withꢀ theseꢀ results,ꢀ itꢀ wasꢀ concludedꢀ thatꢀ tricoordinatedꢀ
RhMe(dcype)ꢀ Aꢀ isꢀ theꢀ trueꢀ intermediateꢀ ofꢀ theꢀ C–Hꢀ bondꢀ
1
activationꢀ stepꢀ (Schemeꢀ 5).ꢀ Hꢀ NMRꢀ analysisꢀ alsoꢀ indicatedꢀ
theꢀreactionꢀwithꢀ HꢀNMRꢀ(Figureꢀ1). ꢀTheꢀrateꢀofꢀtheꢀC–Hꢀbondꢀ
activationꢀ reactionꢀ ofꢀ RhMe(PCy3)(dcype)ꢀ 2ꢀ withꢀ solventꢀ
benzene-d0ꢀ wasꢀ measuredꢀ inꢀ theꢀ presenceꢀ ofꢀ variousꢀ
concentrationsꢀ ofꢀ PCy3.ꢀ Fortunately,ꢀ theꢀ additionꢀ ofꢀ PCy3ꢀ
completelyꢀsuppressedꢀdecompositionꢀofꢀtheꢀcomplex,ꢀandꢀtheꢀ
desiredꢀtransformationꢀproceededꢀquantitativelyꢀaccordingꢀtoꢀ
formationꢀofꢀCH4ꢀinꢀbenzene-d0,ꢀandꢀCH3Dꢀinꢀbenzene-d6.ꢀTheꢀ
detailedꢀ processꢀ ofꢀ C–Hꢀ bondꢀ activationꢀ remainsꢀ unclearꢀ byꢀ
ourꢀ study,ꢀ butꢀ oxidativeꢀ addition–reductiveꢀ eliminationꢀ
processꢀshouldꢀbeꢀtheꢀmostꢀplausible.ꢀForꢀinstance,ꢀSakakuraꢀ
31
16
theꢀ PꢀNMRꢀspectraꢀ(seeꢀSI). ꢀTheꢀreactionꢀwasꢀfoundꢀtoꢀbeꢀ
firstꢀ orderꢀ toꢀ RhMe(PCy3)(dcype)ꢀ 2ꢀ andꢀ inverseꢀ firstꢀ orderꢀ toꢀ
PCy3ꢀ(eq.1).ꢀꢀ
I
reportedꢀ photo-inducedꢀ reactionꢀ ofꢀ Rh Cl(PMe3)3ꢀ inꢀ benzeneꢀ
17,18ꢀ
III
generatedꢀRh (H)(Cl)(Ph)(PMe3)3.
TheꢀformationꢀofꢀmethaneꢀwasꢀalsoꢀconfirmedꢀbyꢀGCꢀanalysisꢀ
ofꢀ theꢀ reactionꢀ mixtureꢀ underꢀ catalyticꢀ conditionsꢀ (Figureꢀ 2).ꢀꢀ
Afterꢀ theꢀ catalyticꢀ carboxylationꢀ ofꢀ benzeneꢀ wasꢀ carriedꢀ outꢀ
underꢀ optimizedꢀ conditionsꢀ byꢀ usingꢀ [RhCl(dcype)]2ꢀ 1ꢀ andꢀ
AlMe1.5(OEt)1.5,ꢀtheꢀgasꢀphaseꢀofꢀtheꢀresultingꢀmixtureꢀwasꢀꢀ
directlyꢀ injectedꢀ toꢀ GC.ꢀ Whileꢀ noꢀ methaneꢀ formationꢀ wasꢀ
observedꢀinꢀtheꢀabsenceꢀofꢀ[RhCl(dcype)]2ꢀ1,ꢀitꢀwasꢀdetectedꢀ
underꢀcatalyticꢀconditions.ꢀ
Cy2
P
Cy2
P
C H or C D
PCy3
Me
6
6
6
6
Ph-dn
Rh
Rh
+
CH4
(CH3D)
P
Cy2
PCy3
P
Cy2
PCy3
7
5 ºC
2
3
•
Reactions in C H6
6
%
$
!
"#
!"!&
"!%#
"!%
R² = 0.99784
= 6.9 ꢀ 10–4 [Mꢁmin–1
]
!
Weꢀ alsoꢀ carriedꢀ outꢀ severalꢀ KIEꢀ studiesꢀ underꢀ theꢀ catalyticꢀ
conditionsꢀ toꢀ determineꢀ theꢀ turnover-limitingꢀ step.ꢀ Itꢀ shouldꢀ
beꢀnotedꢀthatꢀaccurateꢀkineticꢀstudyꢀofꢀthisꢀreactionꢀisꢀdifficultꢀ
underꢀ ourꢀ conditionsꢀ becauseꢀ ofꢀ theꢀ CO2ꢀ concentrationꢀ
problemꢀ (notedꢀ inꢀ theꢀ laterꢀ section)ꢀ andꢀ aꢀ complexꢀ
disproportionationꢀofꢀmethylaluminumꢀreagent.ꢀTherefore,ꢀtheꢀ
resultsꢀ describedꢀ belowꢀ mayꢀ notꢀ beꢀ veryꢀ preciseꢀ butꢀ areꢀ
sufficientꢀforꢀtheꢀgeneralꢀdiscussions.ꢀꢀ
%
k
H
[
3
PCy ] = 0.025 M
!
"#
$
0.036 M
!"!$#
!"!$
!"!!#
!
0.050 M
"#
0.10 M
!
!
%!
&!
'!
(!
$!!
!
$!
%!
&!
–1 [M–1
]
'!
#!
t [min]
[PCy
3
]
Theꢀ KIEsꢀ wereꢀ measuredꢀ byꢀ twoꢀ proceduresꢀ (Schemeꢀ 6).ꢀ Inꢀ
procedureꢀ1,ꢀtheꢀreactionꢀwasꢀperformedꢀusingꢀaꢀ1ꢀ:ꢀ1ꢀmixtureꢀ
ofꢀbenzene-d0ꢀandꢀbenzene-d6.ꢀInꢀprocedureꢀ2,ꢀtheꢀreactionsꢀofꢀ
benzene-d0ꢀ andꢀ benzene-d6ꢀ wereꢀ carriedꢀ outꢀ inꢀ separateꢀ
vessels,ꢀ andꢀ theꢀ resultingꢀ mixturesꢀ wereꢀ combinedꢀ afterꢀ
quenchingꢀtheꢀreactionꢀwithꢀaqueousꢀ1MꢀHCl.ꢀBothꢀreactionsꢀ
wereꢀperformedꢀatꢀ85ꢀºCꢀforꢀ1ꢀh.ꢀTheꢀratioꢀofꢀbenzoicꢀacid-d0ꢀꢀ
•
Reactions in C D6
6
!")
!"(
!"'
!"&
!"%
!"$
!"#
!
!#!!($"
R² = 0.97961
= 1.0 × 10–4 [Mꢁmin–1]ꢀ
!
#!!("
#!!'$"
#!!'"
!#!!&$"
#!!&"
!#!!%$"
#!!%"
k
D
[PCy
3
] = 0.025 M
!
0
.036 M
!
!
0
.050 M
!
!#!!!$"
!"
Cy2
P
Cy2
P
Cy2
P
!
'!
#!!
#'!
$!!
!"
%!"
&!"
'!"
(!"
$!"
+ PhH
Me
Me
Ph
[PCy
3
]–1 [M–1]ꢀ
– PCy3
+ PCy3
*
+,-./0
–
MeH
Rh
Rh
Rh
3
ꢀ
P
Cy2
PCy3
P
Cy2
rds
P
Cy2
+
PCy3
Conditions:ꢀ 0.005ꢀ mmolꢀ 2,ꢀ 0.50ꢀ mLꢀ benzeneꢀ inꢀ NMRꢀ tubeꢀ underꢀ argon.ꢀ Theꢀ
reactionꢀwasꢀanalyzedꢀbyꢀ HꢀNMR.ꢀConsumptionꢀofꢀ2ꢀwasꢀtracedꢀwithꢀdecayꢀofꢀ
1
2
A
C
3
1
3
theꢀ signalꢀ atꢀ δ =ꢀ 0.4 (RhCH ).ꢀ Noꢀ otherꢀ productsꢀ wereꢀ observedꢀ inꢀ Pꢀ NMRꢀ
afterꢀtheꢀreactions.ꢀ
"
active species"
ꢀ
Fig.ꢀ1ꢀꢀKineticsꢀofꢀC–Hꢀbondꢀactivation.ꢀ
Schemeꢀ5ꢀꢀPlausibleꢀpathwayꢀofꢀC–Hꢀbondꢀactivationꢀstep.ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ3ꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
Page 4 of 8
ARTICLEꢀ
JournalꢀNameꢀ
Cy2
P
CO2
(1 atm at 22 ºC)
PCy3
Cy2
P
View Article Online
O CPh
Ph
2
DOI: 10.1039/C6SC03838G
Rh
Rh
P
Cy2
PCy
3
P
PCy
3
toluene-d8
Cy2
D'
3
5 ºC
3
&
!#!*"
#!)"
#!("
#!'"
!#!&"
#!%"
k
obs = kPh1[PCy
3
]-1 + kPh2
!
kPh1 = 2.5 × 10-3 [Mꢁmin–1
]
%
$
!
"#
3
[PCy ] = 0.050 M
-3
–1
kPh2 = 8.0 × 10 [min
]
!
2
R
= 0.9785ꢀ
%
0
.072 M
!
"#
$
0
.10 M
ꢀ
!
0
.20 M
"#
!
a
Theꢀreactionꢀwasꢀcarriedꢀoutꢀinꢀbenzeneꢀatꢀ85ꢀºC.ꢀDetailedꢀreactionꢀconditionsꢀwereꢀ
!#!$"
!"
theꢀsameꢀasꢀshownꢀinꢀSchemeꢀ1.ꢀꢀ
!
$!
%!
&!
'!
#!
!"
("
$!"
$("
]–1 [M–1]ꢀ
3
%!"
%("
t [min]
a
Figureꢀ2ꢀMethaneꢀobservationꢀbyꢀGCꢀanalysis .ꢀ
[
PCy
ꢀ
1
andꢀ benzoicꢀ acid-d5ꢀ wasꢀ estimatedꢀ byꢀ Hꢀ NMRꢀ afterꢀ
Conditions:ꢀ0.005ꢀmmolꢀ3,ꢀ0.50ꢀmLꢀtoluene-d
8
ꢀinꢀNMRꢀtubeꢀ(ca.ꢀ4ꢀmLꢀvol.)ꢀunderꢀ1ꢀatmꢀ
esterificationꢀofꢀbenzoicꢀacidsꢀwithꢀbenzylꢀbromide.ꢀAsꢀaꢀresult,ꢀ
CO .ꢀTheꢀsolutionꢀwasꢀsaturatedꢀwithꢀCO ꢀatꢀ22-23ꢀºCꢀbeforehandꢀ(seeꢀSI).ꢀConsumptionꢀ
2
2
[
(
5-d0]/[5-d5]ꢀ =ꢀ 5.5ꢀ (conditionsꢀ 1)ꢀ andꢀ [5-d0]/[5-d5]ꢀ =ꢀ 4.0ꢀ ofꢀ3ꢀwasꢀtracedꢀwithꢀdecayꢀofꢀtheꢀsignalꢀatꢀ δ 7.9ꢀppmꢀ(Ph).ꢀNoꢀotherꢀproductsꢀwereꢀ
31
observedꢀinꢀ PꢀNMRꢀafterꢀtheꢀreactions.ꢀ
conditionsꢀ 2)ꢀ wereꢀ obtained,ꢀ respectively.ꢀ Theseꢀ largeꢀ KIEꢀ
valuesꢀ indicateꢀ thatꢀ theꢀ C–Hꢀ bondꢀ activationꢀ stepꢀ isꢀ theꢀ
turnover-limitingꢀalsoꢀunderꢀtheꢀcatalyticꢀconditions.ꢀ
Fig.ꢀ3ꢀꢀKineticsꢀofꢀcarboxylationꢀofꢀ3.ꢀꢀ
3
.ꢀMechanisticꢀstudyꢀonꢀtheꢀcarboxylationꢀstepꢀ
Dissociationꢀ ofꢀ PCy3ꢀ wasꢀ clearlyꢀ involvedꢀ alsoꢀ inꢀ theꢀ
–3
carboxylationꢀstep.ꢀTheꢀsmallꢀinterceptꢀtermꢀkPh2ꢀ=ꢀ8.0ꢀxꢀ10 ꢀ
[
Next,ꢀ theꢀ kineticꢀ studyꢀ ofꢀ theꢀ carboxylationꢀ reactionꢀ ofꢀ
RhPh(PCy3)(dcype)ꢀ3ꢀwasꢀcarriedꢀoutꢀunderꢀCO2ꢀ(1ꢀatmꢀatꢀ22-
–1
min ]ꢀleftꢀaꢀpossibilityꢀofꢀaꢀminorꢀpathwayꢀ(e.g.ꢀtheꢀreactionꢀ
19
withoutꢀ dissociationꢀ ofꢀ PCy3),ꢀ butꢀ itꢀ wasꢀ trivialꢀ atꢀ lowerꢀ
concentrationꢀ ofꢀ PCy3.ꢀ Therefore,ꢀ itꢀ isꢀ concludedꢀ thatꢀ theꢀ
carboxylationꢀstepꢀmainlyꢀproceededꢀviaꢀ14-electronꢀcomplexꢀ
RhPh(dcype)ꢀCꢀinꢀaꢀsimilarꢀmannerꢀtoꢀtheꢀC–Hꢀbondꢀactivationꢀ
stepꢀ(Schemeꢀ7).ꢀ
23ꢀºC)ꢀinꢀtheꢀpresenceꢀofꢀPCy3ꢀinꢀtoluene-d8ꢀ(Figureꢀ3). ꢀTheꢀ
valueꢀofꢀ–ln([3]/[3]0)ꢀwasꢀproportionalꢀtoꢀtheꢀreactionꢀtimeꢀandꢀ
wasꢀ almostꢀ inverselyꢀ proportionalꢀ toꢀ [PCy3]ꢀ withꢀ theꢀ rateꢀ
–3
–1
constantꢀkPh1ꢀ=ꢀ2.5ꢀxꢀ10 ꢀ[M·min ]ꢀatꢀ35ꢀºCꢀ(eq.ꢀ2),ꢀsuggestingꢀ
thatꢀ theꢀ carboxylationꢀ stepꢀ isꢀ muchꢀ fasterꢀ thanꢀ theꢀ C–Hꢀ
activationꢀstep,ꢀwhichꢀcoincidedꢀwithꢀtheꢀresultsꢀofꢀKIEꢀstudies.ꢀꢀ
Theꢀ carboxylationꢀ reactionꢀ ofꢀ RhMe(PCy3)(dcype)ꢀ 2ꢀ wasꢀ alsoꢀ
20
carriedꢀ outꢀ inꢀ toluene-d8ꢀ atꢀ 35ꢀ ºCꢀ (Figureꢀ 4). ꢀ 2ꢀ showedꢀ
somewhatꢀ lowerꢀ reactivityꢀ ofꢀ carboxylationꢀ comparedꢀ toꢀ
–
ln ! ! ! = (!!"# PCy! –! + !!"#) !
2
-3
–1
= 2.5 × 10!! M ∙ min!!
RhPh(PCy3)(dcype)ꢀ3ꢀ(eq.3,ꢀkMe1ꢀ=ꢀ1.0ꢀxꢀ10 ꢀ[M·min ]ꢀvsꢀkPh1ꢀ=ꢀ
!!"#
-
3
–1
.5ꢀxꢀ10 ꢀ[M·min ]).ꢀꢀ
2
!!"#
= 8.0 × 10!! [min!!
]
–
ln ! ! ! = !!"# PCy! –!
!
3
Procedure 1: in the same vessel
x 10-3 mmol 1
= 1.0 × 10!! M ∙ min!!
!!"#
5
1
1
.1 mmol AlMe1.5(OEt)1.5
CO Bn
TheꢀequationꢀwasꢀsimilarꢀtoꢀthatꢀofꢀRhPh(PCy3)(dcype)ꢀ3ꢀexceptꢀ
completeꢀ disappearanceꢀ ofꢀ theꢀ interceptꢀ termꢀ (kMe2ꢀ =ꢀ 0),ꢀ
suggestingꢀ intermediacyꢀ ofꢀ RhMe(dcype)ꢀ Aꢀ asꢀ aꢀ reactiveꢀ
2
atm CO2
BnBr
dn
0
6
.1 mL DMA
µL TMU
dn
-dn
[5-d ]/[5-d ]
1
31
4
-dn
5
species.ꢀ Hꢀ andꢀ Pꢀ NMRꢀ indicatedꢀ noꢀ formationꢀ ofꢀ C–Hꢀ
activationꢀ productꢀ Rh(tol)(PCy3)(dcype)ꢀ orꢀ correspondingꢀ
benzoatesꢀ throughoutꢀ theꢀ reaction.ꢀ Inꢀ addition,ꢀ theꢀ
stoichiometricꢀ reactionꢀ ofꢀ RhMe(PCy3)(dcype)ꢀ 2ꢀ underꢀ 1ꢀ atmꢀ
CO2ꢀinꢀbenzeneꢀatꢀ85ꢀºCꢀdidꢀnotꢀgiveꢀbenzoatesꢀatꢀall,ꢀbutꢀgaveꢀ
onlyꢀ acetatesꢀ Rh(OAc)(dcype)ꢀ Eꢀ andꢀ Rh(OAc)(PCy3)(dcype)ꢀ E’ꢀ
85 °C, 1 h, closed
d0 : d6
mL : 1 mL
0
5
1
= 5.5 ± 0.5
Procedure 2: in the separate vessels
as above
(Schemeꢀ8).ꢀTheseꢀresultsꢀimplyꢀcarboxylationꢀofꢀRhMe(dcype)ꢀ
AꢀwithꢀCO2ꢀproceededꢀmuchꢀfasterꢀthanꢀC–HꢀactivationꢀofꢀAꢀꢀ
4
CO Bn
2
combine
BnBr
2
mL
dn
Cy2
P
Cy2
P
–
+
PCy3
as above
5-dn
Ph
+ CO2
O
O
+ PCy3
Ph
D'
d6
3
Rh
Rh
[
=
5-d ]/[5-d ]
0
4.0
5
PCy3
P
Cy2
P
Cy2
4
-d6
2
mL
ꢀ
C
D
"
active species"
Schemeꢀ6ꢀꢀKIEꢀstudyꢀunderꢀcatalyticꢀconditions.ꢀ
ꢀ
Schemeꢀ7ꢀꢀPlausibleꢀpathwayꢀofꢀcarboxylationꢀstep.ꢀꢀ
4
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Page 5 of 8
Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
JournalꢀNameꢀ
ꢀARTICLEꢀ
Cy2
P
1 atm CO2
PCy3
Cy2
P
5 x 10-3 mmol
[RhCl(dcype)]2
1.1 mmol AlMe1.5(OEt)1.5
1 atm CO2 (40 cm3)
View Article Online
DOI: 10.1039/C6SC03838G
Me
O CMe
2
1
Rh
Rh
toluene-d8
CO H
P
Cy2
PCy
3
P
Cy2
PCy
3
H+
2
3
5 ºC
+
AcOH
2
E'
DMA (0.1 mL), TMU (6 µL)
8
5 ºC, 6 h
4
6
'
'
'
"%
"$
"#
'
!#!&$"
k
k
obs = kMe1[PCy
Me1 = 1.0 × 10 [Mꢁmin–1
3
]-1
TON 40 (NMR)
60 (GC)
-3
ꢀ
]
!#!&"
[PCy ] = 0.050 M
3
R² = 0.99143
0
.072 M
Schemeꢀ9ꢀꢀConfirmationꢀofꢀaceticꢀacidꢀformation.ꢀ
!
#!%$"
!#!%"
#!!$"
!"&
!"%
!"$
!"#
!
1ꢀhꢀtoꢀreduceꢀeffectsꢀofꢀcatalystꢀdecompositionꢀandꢀreagentꢀ
ꢀ
consumptions. Theꢀstirringꢀrateꢀwasꢀkeptꢀca.ꢀ800ꢀrpm.ꢀTheꢀ
0.10 M
!
3
reactionꢀapparatusesꢀwere;ꢀaꢀ40ꢀcm ꢀtestꢀtubeꢀ(øꢀ=ꢀ2ꢀcm,ꢀvesselꢀ
0
.20 M
!"
3
)ꢀwithꢀaꢀclosedꢀsystemꢀ(entryꢀ1),ꢀaꢀ40ꢀcm ꢀtestꢀtubeꢀ(vesselꢀ1)ꢀ
!
#!
$!
%!
&!
1
withꢀ aꢀ 2000ꢀ cm ꢀ balloonꢀ filledꢀ withꢀ CO2ꢀ toꢀ disregardꢀ theꢀ
!"
$"
%!"
%$"
&!"
&$"
t [min]
]–1 [M–1]ꢀ
PCy
3
3
[
ꢀ
3
decreaseꢀofꢀCO2ꢀinꢀaꢀwholeꢀvesselꢀ(entryꢀ2),ꢀaꢀ40ꢀcm ꢀround-
3
bottomꢀflaskꢀ(vesselꢀ2)ꢀwithꢀaꢀ2000ꢀcm ꢀballoonꢀ(entryꢀ3)ꢀandꢀaꢀ
Conditions:ꢀ0.005ꢀmmolꢀ2,ꢀ0.50ꢀmLꢀtoluene-d
CO .ꢀTheꢀsolutionꢀwasꢀsaturatedꢀwithꢀCO
8
ꢀinꢀNMRꢀtubeꢀ(ca.ꢀ4ꢀmLꢀvol.)ꢀunderꢀ1ꢀatmꢀ
3
ꢀatꢀ22-23ꢀºCꢀbeforehandꢀ(seeꢀSI).ꢀConsumptionꢀ 160ꢀ cm ꢀ round-bottomꢀ flaskꢀ (vesselꢀ 3)ꢀ withꢀ aꢀ closedꢀ systemꢀ
2
2
ofꢀ2ꢀwasꢀtracedꢀwithꢀdecayꢀofꢀtheꢀsignalꢀatꢀδ 0.4 ppm (CH
3
).ꢀ
(entryꢀ 4).ꢀ Inꢀ entryꢀ 4,ꢀ theꢀ contentꢀ ofꢀ CO ꢀ shouldꢀ alsoꢀ beꢀ
2
sufficientꢀ(ca.ꢀ7ꢀmmol).ꢀꢀ
Fig.ꢀ4ꢀꢀKineticsꢀofꢀcarboxylationꢀofꢀ2.ꢀ
Itꢀ wasꢀ foundꢀ thatꢀ theꢀ volumeꢀ ofꢀ theꢀ apparatusꢀ wasꢀ notꢀ soꢀ
influentialꢀonꢀtheꢀratioꢀofꢀbenzoicꢀacidꢀandꢀaceticꢀacid,ꢀbutꢀtheꢀ
shapeꢀofꢀtheꢀvesselꢀcausedꢀaꢀdramaticꢀdifference.ꢀTheꢀvalueꢀofꢀ
withꢀbenzeneꢀunderꢀ1ꢀatmꢀCO2.ꢀInꢀotherꢀwords,ꢀpredominantꢀ
formationꢀ ofꢀ aceticꢀ acidꢀ shouldꢀ associateꢀ withꢀ formationꢀ ofꢀ
benzoicꢀacid.ꢀꢀ
[
BzOH]/[AcOH]ꢀinꢀvesselꢀ1ꢀwasꢀ0.12ꢀwithoutꢀaꢀballoonꢀandꢀ0.14ꢀ
withꢀaꢀballoonꢀ(entryꢀ1ꢀvsꢀ2).ꢀItꢀindicatedꢀtheꢀtotalꢀcontentꢀofꢀ
CO2ꢀwasꢀnotꢀresponsibleꢀforꢀtheꢀselectivityꢀinꢀinitialꢀ1ꢀhꢀofꢀtheꢀ
Basedꢀonꢀtheꢀaboveꢀconsideration,ꢀTONꢀofꢀaceticꢀacidꢀ(AcOH)ꢀ
wasꢀ estimatedꢀ byꢀ GCꢀ analysisꢀ underꢀ theꢀ catalyticꢀ conditions.ꢀ
Accordingꢀ toꢀ theꢀ standardꢀ catalyticꢀ procedure,ꢀ theꢀ reactionꢀ
22
reactionꢀ time. ꢀ Inꢀ sharpꢀ contrast,ꢀ theꢀ useꢀ ofꢀ vesselꢀ 2ꢀ
decreasedꢀ[BzOH]/[AcOH]ꢀtoꢀ0.03ꢀ(entryꢀ2ꢀvsꢀ3).ꢀTheꢀformationꢀ
ofꢀaceticꢀacidꢀwasꢀpredominantꢀwhenꢀvesselꢀ3ꢀwasꢀemployedꢀꢀ
3
wasꢀcarriedꢀoutꢀinꢀ40ꢀcm ꢀtestꢀtubeꢀforꢀ6ꢀhꢀatꢀ85ꢀºCꢀwithꢀtheꢀ
tubeꢀkeptꢀclosed.ꢀAsꢀweꢀexpected,ꢀitꢀwasꢀfoundꢀthatꢀinꢀadditionꢀ
toꢀ ca.ꢀ 0.40ꢀ mmolꢀ (TONꢀ =ꢀ 40)ꢀ ofꢀ benzoicꢀ acid,ꢀ ca.ꢀ 0.6ꢀ mmolꢀ
(
entryꢀ4,ꢀ[BzOH]/[AcOH]ꢀ=ꢀ0.01)ꢀasꢀobservedꢀinꢀtheꢀreactionꢀofꢀ
RhMe(PCy3)(dcype)ꢀ2ꢀunderꢀCO2ꢀinꢀbenzeneꢀ(Schemeꢀ8).ꢀ
TONꢀ=ꢀca.ꢀ60)ꢀofꢀaceticꢀacidꢀwasꢀproducedꢀasꢀjudgedꢀbyꢀGCꢀ
(
analysisꢀ(Schemeꢀ9).ꢀHowever,ꢀtheꢀratioꢀofꢀBzOHꢀ:ꢀAcOHꢀ=ꢀ2ꢀ:ꢀ3ꢀ
wasꢀ stillꢀ inconsistentꢀ withꢀ theꢀ resultꢀ ofꢀ theꢀ stoichiometricꢀ
study.ꢀ Toꢀ obtainꢀ moreꢀ informationꢀ onꢀ theꢀ competitiveꢀ
formationꢀofꢀbenzoicꢀacidꢀandꢀaceticꢀacid,ꢀweꢀdecidedꢀtoꢀcarryꢀ
outꢀ moreꢀ detailedꢀ analysisꢀ ofꢀ theꢀ reactionsꢀ toꢀ clarifyꢀ theꢀ
differenceꢀofꢀtheseꢀstoichiometricꢀandꢀcatalyticꢀreactions.ꢀꢀ
a
Tableꢀ1ꢀꢀEffectꢀofꢀCO
2
ꢀcontentꢀandꢀtheꢀshapeꢀofꢀtheꢀvessel. ꢀ
3ꢀ
Allꢀtheꢀreactionsꢀsoꢀfarꢀhaveꢀbeenꢀcarriedꢀoutꢀusingꢀ40ꢀcm testꢀ
tubeꢀ(ca.ꢀ2ꢀmmolꢀofꢀCO2ꢀshouldꢀbeꢀinside)ꢀinꢀaꢀclosedꢀsystemꢀ
forꢀ theꢀ catalyticꢀ reaction,ꢀ andꢀ ca.ꢀ 1ꢀ mmolꢀ ofꢀ CO2ꢀ wasꢀ
consumedꢀtoꢀproduceꢀbenzoicꢀacidꢀandꢀaceticꢀacidꢀasꢀshownꢀinꢀ
Schemeꢀ9.ꢀAsꢀtheꢀamountꢀofꢀCO2ꢀinꢀtheꢀreactionꢀmixtureꢀwasꢀ
thoughtꢀtoꢀbeꢀinfluentialꢀonꢀtheꢀratioꢀofꢀcarboxylicꢀacidsꢀunderꢀ
theꢀ catalyticꢀ conditions,ꢀ theꢀ reactionꢀ wasꢀ examinedꢀ usingꢀ
severalꢀapparatusesꢀwithꢀdifferentꢀshapeꢀandꢀvolume.ꢀꢀ
ꢀ
Theꢀ effectꢀ ofꢀ theꢀ reactionꢀ apparatusꢀ wasꢀ examinedꢀ byꢀ
changingꢀtheꢀtotalꢀvolumeꢀofꢀtheꢀapparatusꢀand/orꢀtheꢀshapeꢀ
totalꢀꢀ
TONꢀꢀ
[
BzOH]/ꢀ
entryꢀ conditionsꢀꢀ
volumeꢀ
21
3
[BzOH]ꢀ
7.9ꢀ
[AcOH]ꢀ
68ꢀ
[AcOH]ꢀ
ofꢀtheꢀreactionꢀvesselꢀ(Tableꢀ1). ꢀTheꢀreactionꢀtimeꢀwasꢀsetꢀtoꢀꢀ
ꢀ(cm )ꢀ
1
2
ꢀ
ꢀ
vesselꢀ1ꢀꢀ
vesselꢀ1ꢀꢀ+ꢀ
balloonꢀ
40ꢀ
0.12ꢀ
0.14ꢀ
Cy2
P
Cy
P
2
Cy
P
2
1 atm
CO2
40+2000ꢀ
5.7ꢀ
42ꢀ
Me
O CMe
2
O CPh
2
Rh
Rh
2
Rh
2
vesselꢀ2ꢀ
benzene
3ꢀ
40+2000ꢀ
160ꢀ
2.5ꢀ
1.3ꢀ
84ꢀ
0.03ꢀ
0.01ꢀ
P
PCy3
P
Cy
(PCy3)
P
(PCy3)
8
5 ºC
5 min
+ꢀballoonꢀ
vesselꢀ3ꢀꢀ
Cy2
Cy
1
4
ꢀ
147ꢀ
2
E + E'
D + D'
not detected
a
3
3
ꢀ
Vesselꢀ1:ꢀaꢀ40ꢀcm ꢀtestꢀtubeꢀ(øꢀ=ꢀ2ꢀcm),ꢀVesselꢀ2:ꢀaꢀ40ꢀcm ꢀround-bottomꢀflask,ꢀ
3
Vesselꢀ 3:ꢀ aꢀ 160ꢀ cm ꢀ round-bottomꢀ flask.ꢀ Conditionsꢀ wereꢀ shownꢀ inꢀ Schemeꢀ 9,ꢀ
exceptꢀthatꢀtheꢀreactionꢀtimeꢀwasꢀshortenedꢀtoꢀ1ꢀh.ꢀStirringꢀratesꢀwereꢀapprox.ꢀ
Schemeꢀ8.ꢀStoichiometricꢀCarboxylationꢀofꢀ2ꢀatꢀ85ꢀºC.ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
8
00ꢀrpm.ꢀꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ5ꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
Page 6 of 8
ARTICLEꢀ
JournalꢀNameꢀ
Thisꢀlargeꢀeffectꢀofꢀtheꢀshapeꢀofꢀtheꢀvesselꢀwouldꢀbeꢀdueꢀtoꢀtheꢀ Tableꢀ2ꢀꢀEffectꢀofꢀstirringꢀrate.ꢀ
dissolutionꢀrateꢀofꢀCO2ꢀintoꢀsolution,ꢀwhichꢀwasꢀelucidatedꢀbyꢀ
View Article Online
DOI: 10.1039/C6SC03838G
23
ꢀ
ꢀ
TONꢀ
ꢀ
inꢀ situ-IRꢀ analysisꢀ atꢀ roomꢀ temperatureꢀ (Figureꢀ 5). ꢀ CO2ꢀ
3
dissolutionꢀ occurredꢀ moreꢀ rapidlyꢀ inꢀ aꢀ 40ꢀ cm ꢀ round-bottomꢀ
rateꢀ
rpm]ꢀ
entryꢀ
[BzOH]ꢀ
[AcOH]ꢀ
[BzOH]/[AcOH]ꢀ
[
3
flaskꢀthanꢀinꢀaꢀ40ꢀcm ꢀtestꢀtubeꢀevenꢀthoughꢀtheyꢀhaveꢀalmostꢀ
1
2
3
ꢀ
ꢀ
ꢀ
100ꢀ
800ꢀ
8.3ꢀ
7.9ꢀ
6.2ꢀ
33ꢀ
68ꢀ
93ꢀ
0.25ꢀ
0.12ꢀ
0.07ꢀ
theꢀ sameꢀ totalꢀ volume.ꢀ Forꢀ instance,ꢀ theꢀ CO2ꢀ concentrationꢀ
reachedꢀ saturationꢀ withinꢀ 200ꢀ secondsꢀ inꢀ theꢀ round-bottomꢀ
flask.ꢀOnꢀtheꢀotherꢀhand,ꢀitꢀtookꢀalmostꢀ1000ꢀsecondsꢀinꢀtheꢀ
1000ꢀ
3
testꢀ tube.ꢀ Althoughꢀ theꢀ resultsꢀ shownꢀ hereꢀ wereꢀ obtainedꢀ Reactionsꢀwereꢀcarriedꢀoutꢀinꢀ40ꢀcm ꢀtestꢀtubesꢀ(closedꢀsystem).ꢀꢀConditionsꢀwereꢀ
theꢀsameꢀasꢀnotedꢀinꢀTableꢀ1.ꢀꢀ
withoutꢀ stirring,ꢀ theꢀ rateꢀ ofꢀ dissolutionꢀ ofꢀ CO2ꢀ certainlyꢀ
dependsꢀonꢀtheꢀsurfaceꢀareaꢀofꢀtheꢀsolution,ꢀwhichꢀinfluencedꢀ
concentrationꢀofꢀCO2ꢀinꢀtheꢀliquidꢀphaseꢀwasꢀmuchꢀlowerꢀthanꢀ
theꢀratioꢀofꢀBzOHꢀandꢀAcOH.ꢀForꢀtheꢀsameꢀreason,ꢀtheꢀstirringꢀ
saturationꢀ dueꢀ toꢀ itsꢀ consumptionꢀ byꢀ theꢀ carboxylationꢀ
rateꢀ wasꢀ alsoꢀ foundꢀ toꢀ beꢀ responsibleꢀ (Tableꢀ 2).ꢀ Theꢀ slowerꢀ
stirringꢀ gaveꢀ anꢀ improvedꢀ ratioꢀ ofꢀ [BzOH]/[AcOH],ꢀ althoughꢀ
reactionꢀ ofꢀ RhMe(dcype)ꢀ A.ꢀ Thus,ꢀ dissolutionꢀ rateꢀ ofꢀ CO2ꢀ
controlledꢀtheꢀfateꢀofꢀtheꢀkeyꢀintermediateꢀRhMe(dcype)ꢀA.ꢀItꢀ
totalꢀ TONꢀ decreased.ꢀ Forꢀ example,ꢀ [BzOH]/[AcOH]ꢀ wasꢀ 0.25ꢀ
clearlyꢀindicatesꢀtheꢀbalanceꢀbetweenꢀC–Hꢀbondꢀactivationꢀandꢀ
andꢀtotalꢀTONꢀwasꢀ41ꢀatꢀ100ꢀrpm,ꢀwhileꢀ[BzOH]/[AcOH]ꢀwasꢀ
theꢀ subsequentꢀ transformationꢀ isꢀ veryꢀ importantꢀ forꢀ theꢀ
0
.07ꢀandꢀtotalꢀTONꢀwasꢀ99ꢀatꢀ1000ꢀrpm.ꢀꢀ
catalyticꢀC–Hꢀbondꢀfunctionalizationꢀreactionꢀusingꢀtheseꢀalkylꢀ
metalꢀcomplexes.ꢀ
Fromꢀtheseꢀresults,ꢀitꢀwasꢀconcludedꢀthatꢀthisꢀreactionꢀstronglyꢀ
dependsꢀonꢀCO2ꢀconcentrationꢀinꢀtheꢀliquidꢀphase,ꢀwhichꢀwasꢀ
mainlyꢀ determinedꢀ byꢀ theꢀ dissolutionꢀ rateꢀ ofꢀ CO2.ꢀ Inꢀ otherꢀ
words,ꢀtheꢀliquidꢀphaseꢀisꢀnotꢀsaturatedꢀwithꢀCO2ꢀowingꢀtoꢀitsꢀ
fastꢀ consumptionꢀ byꢀ carboxylationꢀ reactionsꢀ underꢀ catalyticꢀ
conditions.ꢀ Inꢀ theꢀ presenceꢀ ofꢀ sufficientꢀ CO2,ꢀ intermediateꢀ
RhMe(dcype)ꢀ Aꢀ mostlyꢀ reactsꢀ withꢀ CO2ꢀ toꢀ giveꢀ aceticꢀ acidꢀ
beforeꢀ itꢀ reactsꢀ withꢀ benzeneꢀ toꢀ giveꢀ RhPh(dcype)ꢀ Cꢀ asꢀ
observedꢀinꢀentryꢀ4ꢀinꢀTableꢀ1ꢀandꢀentryꢀ3ꢀinꢀTableꢀ2,ꢀandꢀitꢀ
agreesꢀ withꢀ theꢀ resultꢀ ofꢀ theꢀ stoichiometricꢀ reactionꢀ ofꢀ
RhMe(PCy3)(dcype)ꢀ2ꢀinꢀCO2-saturatedꢀbenzene.ꢀHowever,ꢀtheꢀ
trueꢀconcentrationꢀofꢀCO2ꢀshouldꢀbeꢀratherꢀlowꢀunderꢀcatalyticꢀ
conditionsꢀparticularlyꢀwithꢀslowerꢀstirringꢀandꢀaꢀliquidꢀphaseꢀ
withꢀaꢀsmallerꢀsurfaceꢀarea.ꢀThen,ꢀcarboxylationꢀandꢀC–Hꢀbondꢀ
activationꢀofꢀbenzeneꢀbyꢀRhMe(dcype)ꢀAꢀbecomesꢀcompetitiveꢀ
underꢀsuchꢀconditions,ꢀandꢀbothꢀbenzoicꢀacidꢀandꢀaceticꢀacidꢀ
wereꢀ obtainedꢀ catalyticallyꢀ inꢀ contrastꢀ toꢀ theꢀ stoichiometricꢀ
reactionꢀofꢀRhMe(PCy3)(dcype)ꢀ2.ꢀ
4
.ꢀTransmetallationꢀBehaviorsꢀꢀ
Directꢀobservationꢀofꢀtheꢀreactionꢀmixtureꢀisꢀaꢀreliableꢀmethodꢀ
toꢀobtainꢀinformationꢀonꢀtheꢀrestingꢀstateꢀofꢀtheꢀcatalyticꢀcycle.ꢀ
31
Weꢀ thenꢀ observedꢀ Pꢀ NMRꢀ toꢀ clarifyꢀ theꢀ rhodiumꢀ speciesꢀ
presentꢀinꢀtheꢀreactionꢀmixtureꢀafterꢀtheꢀcatalyticꢀreactionꢀwasꢀ
carriedꢀ outꢀ inꢀ benzeneꢀ forꢀ 1ꢀ hꢀ underꢀ 1ꢀ atmꢀ CO2ꢀ atꢀ 85ꢀ ºCꢀ
(
Schemeꢀ10).ꢀItꢀwasꢀaꢀsurpriseꢀtoꢀfindꢀthatꢀalmostꢀnoꢀcomplexꢀ
exceptꢀ forꢀ theꢀ startingꢀ [RhCl(dcype)]2ꢀ 1ꢀ wasꢀ observedꢀ evenꢀ
thoughꢀ benzoicꢀ acidꢀ wasꢀ producedꢀ gradually.ꢀ Alternatively,ꢀ
onlyꢀ1ꢀwasꢀobservedꢀunderꢀargonꢀalso.ꢀNoꢀmethylrhodiumꢀorꢀ
ꢀ
phenylrhodiumꢀspeciesꢀwereꢀobserved.ꢀ[RhCl(dcype)]2 1ꢀmostlyꢀ
decomposedꢀafterꢀ6ꢀhꢀofꢀheatingꢀunderꢀAr.ꢀTherefore,ꢀitꢀwasꢀ
speculatedꢀthatꢀthereꢀwouldꢀbeꢀequilibriaꢀbetweenꢀA-Dꢀtoꢀ1,ꢀsoꢀ
thatꢀonlyꢀ1ꢀwasꢀobservable.ꢀ
Toꢀconfirmꢀourꢀspeculation,ꢀRh(O2CPh)(dcype)ꢀDꢀwasꢀpreparedꢀ
andꢀ itsꢀ catalyticꢀ activityꢀ wasꢀ examined.ꢀ Whenꢀ theꢀ catalyticꢀ
carboxylationꢀreactionꢀofꢀbenzeneꢀwasꢀcarriedꢀoutꢀusingꢀDꢀasꢀaꢀ
catalyst,ꢀ benzoicꢀ acidꢀ wasꢀ obtainedꢀ inꢀ TONꢀ ofꢀ onlyꢀ 2.5.ꢀ Inꢀ
addition,ꢀ whenꢀ Dꢀ andꢀ excessꢀ AlMe1.5(OEt)1.5ꢀ wereꢀ mixedꢀ inꢀ
benzeneꢀ atꢀ roomꢀ temperatureꢀ (noꢀ chlorideꢀ source),ꢀ rapidꢀ
Inꢀsummary,ꢀweꢀprovedꢀ14-electronꢀtricoodinatedꢀRhPh(dcype)ꢀ
Cꢀ isꢀ aꢀ plausibleꢀ intermediateꢀ inꢀ theꢀ carboxylationꢀ step.ꢀ
RhMe(dcype)ꢀAꢀalsoꢀreactedꢀwithꢀCO2ꢀinꢀaꢀsimilarꢀwayꢀtoꢀgiveꢀ
aceticꢀ acidꢀ catalytically.ꢀ Thisꢀ undesiredꢀ pathwayꢀ wasꢀ
predominantꢀoverꢀdesiredꢀC–Hꢀbondꢀactivationꢀreactionꢀunderꢀ
31
decompositionꢀ ofꢀ theꢀ complexꢀ wasꢀ observedꢀ byꢀ Pꢀ NMRꢀ
(Schemeꢀ11).ꢀHowever,ꢀitꢀwasꢀfoundꢀthatꢀadditionꢀofꢀonlyꢀanꢀ
ꢀatmꢀCO2.ꢀNevertheless,ꢀC–Hꢀbondꢀactivationꢀofꢀbenzeneꢀtookꢀ
1
equimolarꢀ amountꢀ ofꢀ AlClMe2ꢀ toꢀ Dꢀ preventedꢀ itꢀ fromꢀ
decompositionꢀ toꢀ giveꢀ [RhCl(dcype)]2ꢀ 1,ꢀ andꢀ theꢀ catalyticꢀ
activityꢀwasꢀrecoveredꢀ(TONꢀ28).ꢀInꢀotherꢀwords,ꢀtheꢀsuccessꢀofꢀ
theꢀ presentꢀ reactionꢀ wasꢀ dueꢀ toꢀ theꢀ fastꢀ transmetallationꢀ ofꢀ
ratherꢀ unstableꢀ [Rh]-O2CPhꢀ orꢀ [Rh]-Meꢀ withꢀ [Al]-Clꢀ toꢀ giveꢀ
stableꢀdimericꢀ[Rh]-Clꢀspeciesꢀunderꢀtheꢀcatalyticꢀconditions.ꢀꢀ
ꢀ
placeꢀsuccessfullyꢀunderꢀtheꢀcatalyticꢀconditionsꢀbecauseꢀtheꢀꢀ
Cy2
P
AlMe1.5(OEt)1.5
Cl
(excess)
Rh
2
(1 recovered)
P
Cy2
benzene:DMA:TMU
1000 : 50 : 3)
CO2 or Ar, 85 ºC, 1 h
(
a
-1
3
1
2
DissolutionꢀofꢀCO ꢀwasꢀtracedꢀbyꢀinꢀsitu-IRꢀspectrometryꢀ(2350ꢀcm )ꢀinꢀ2ꢀcm ꢀ
ꢀ
tolueneꢀatꢀroomꢀtemperature.ꢀTheꢀmixturesꢀwereꢀstoodꢀwithoutꢀstirringꢀduringꢀ
measurements.ꢀ
3
Schemeꢀ10ꢀꢀAnalysisꢀofꢀtheꢀreactionꢀmixtureꢀbyꢀ PꢀNMR.ꢀ
1
a
ꢀinꢀtoluene. ꢀ
Fig.ꢀ5ꢀꢀDissolutionꢀofꢀCO
2
6
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Page 7 of 8
Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
JournalꢀNameꢀ
ꢀARTICLEꢀ
Cy2
P
20 equiv.
AlMe1.5(OEt)1.5
Theꢀ undesiredꢀ formationꢀ ofꢀ Eꢀ shouldꢀ beꢀ opeVraietwivAertiꢀcliefOꢀ ntlhineeꢀ
DOI: 10.1039/C6SC03838G
reactionꢀmixtureꢀcontainsꢀsufficientꢀamountꢀofꢀCO2ꢀinꢀsolution.ꢀ
O
O
almost
decomposed
Rh
Ph
benzene
rt
Nevertheless,ꢀ theꢀ desiredꢀ C–Hꢀ bondꢀ activationꢀ takesꢀ placeꢀ
becauseꢀ theꢀ trueꢀ concentrationꢀ ofꢀ CO2ꢀ inꢀ solutionꢀ isꢀ muchꢀ
lowerꢀ thanꢀ saturation.ꢀ Importantly,ꢀ theꢀ catalyticꢀ reactionꢀ didꢀ
notꢀ workꢀ wellꢀ inꢀ theꢀ absenceꢀ ofꢀ theꢀ chlorideꢀ source.ꢀ Thisꢀ isꢀ
probablyꢀbecauseꢀtricoordinatedꢀactiveꢀspeciesꢀRhMe(dcype)ꢀAꢀ
wasꢀ tooꢀ unstableꢀ toꢀ beꢀ presentꢀ inꢀ higherꢀ concentrationꢀ andꢀ
decompositionꢀ ofꢀ theꢀ Rhꢀ speciesꢀ occurred.ꢀ Theꢀ presenceꢀ ofꢀ
chlorideꢀspeciesꢀkeepsꢀtheꢀrestingꢀstateꢀofꢀtheꢀrhodiumꢀspeciesꢀ
asꢀ[RhCl(dcype)]2ꢀ1,ꢀwhichꢀhasꢀstableꢀtetracoordinatedꢀdimericꢀ
structureꢀandꢀmoderatelyꢀreactiveꢀtoꢀtransmetallationꢀwithꢀAl-
Meꢀ species.ꢀ Thisꢀ equilibriumꢀ limitedꢀ theꢀ concentrationꢀ ofꢀ
activeꢀ speciesꢀ RhMe(dcype)ꢀ Aꢀ andꢀ suppressedꢀ itsꢀ
decomposition.ꢀ Transmetallationꢀ stepsꢀ haveꢀ attractedꢀ lessꢀ
interestꢀinꢀmechanisticꢀstudies,ꢀandꢀtheirꢀpossibleꢀequilibriaꢀareꢀ
mostlyꢀ ignored.ꢀ Ourꢀ observationꢀ shouldꢀ beꢀ anꢀ interestingꢀ
exampleꢀ toꢀ showꢀ theꢀ importanceꢀ ofꢀ theꢀ transmetallationꢀ
equilibriaꢀinꢀtheꢀcatalyticꢀcycle.ꢀ
P
Cy2
(dark solution)
D
2
0 equiv.
AlMe1.5(OEt)1.5
1 equiv. AlClMe2
(all at once)
Cy2
P
Cy2
P
O
O
Cl
Rh
Ph
Rh
2
P
Cy2
benzene
rt
P
Cy2
D
1
(yellow solution)
ꢀ
2
Schemeꢀ11ꢀꢀTransmetallationꢀofꢀRh–O CPhꢀcomplex.ꢀ
TheꢀtotalꢀfigureꢀofꢀthisꢀreactionꢀisꢀillustratedꢀinꢀSchemeꢀ12.ꢀTheꢀ
mostꢀ importantꢀ cycle,ꢀ whichꢀ providesꢀ benzoicꢀ acid,ꢀ isꢀ
confirmedꢀ toꢀ beꢀ fundamentallyꢀ theꢀ sameꢀ asꢀ weꢀ postulatedꢀ
(
[
depictedꢀ inꢀ boldꢀ arrows).ꢀ First,ꢀ transmetallationꢀ ofꢀ
RhCl(dcype)]2ꢀ 1ꢀ andꢀ AlMe1.5(OEt)1.5ꢀ generatesꢀ 14-electronꢀ
methylrhodiumꢀ complexꢀ RhMe(dcype)ꢀ A.ꢀ Aꢀ reactsꢀ withꢀ
benzeneꢀtoꢀgiveꢀ14-electronꢀphenylrhodiumꢀcomplexꢀꢀ
RhPh(dcype)ꢀC,ꢀpossiblyꢀviaꢀreductiveꢀeliminationꢀofꢀmethaneꢀ Conclusionsꢀ
fromꢀRh(H)(Me)(Ph)(dcype)ꢀB.ꢀTheꢀfollowingꢀcarboxylationꢀofꢀCꢀ
Thisꢀ articleꢀ describedꢀ aꢀ detailedꢀ mechanisticꢀ analysisꢀ ofꢀ
providesꢀ rhodiumꢀ benzoateꢀ Rh(O2CPh)(dcype)ꢀ D.ꢀ Thereꢀ areꢀ
twoꢀpossibleꢀpathwaysꢀinꢀtheꢀnextꢀstep.ꢀTransmetallationꢀofꢀDꢀ
andꢀ chloroaluminumꢀ speciesꢀ convertsꢀ backꢀ theꢀ catalystꢀ toꢀ
rhodium-catalyzedꢀ carboxylationꢀ ofꢀ simpleꢀ aromaticꢀ
compounds.ꢀ Althoughꢀ noꢀ activeꢀ intermediatesꢀ wereꢀ
observableꢀatꢀallꢀinꢀthisꢀreaction,ꢀtheꢀproposedꢀmechanismꢀwasꢀ
mostlyꢀ supportedꢀ byꢀ severalꢀ experiments.ꢀ Mostꢀ importantly,ꢀ
elucidationꢀ ofꢀ theꢀ activeꢀ speciesꢀ wasꢀ achievedꢀ byꢀ designingꢀ
appropriateꢀ precursors andꢀ theꢀ followingꢀ kineticꢀ studies.ꢀ 14-
electronꢀ rhodiumꢀ complexesꢀ wereꢀ foundꢀ toꢀ beꢀ theꢀ keyꢀ
intermediatesꢀ inꢀ bothꢀ ofꢀ C–Hꢀ bondꢀ activationꢀ andꢀ
carboxylationꢀ steps.ꢀ Theꢀ presenceꢀ ofꢀ suchꢀ speciesꢀ wasꢀ alsoꢀ
supportedꢀ byꢀ theꢀ formationꢀ ofꢀ methaneꢀ andꢀ aceticꢀ acid.ꢀ KIEꢀ
studyꢀ underꢀ theꢀ catalyticꢀ conditionsꢀ revealedꢀ thatꢀ theꢀ C–Hꢀ
bondꢀactivationꢀstepꢀwasꢀtheꢀturnover-limitingꢀstep.ꢀAccordingꢀ
toꢀtheꢀkineticꢀstudies,ꢀthisꢀC–Hꢀbondꢀactivationꢀstepꢀshouldꢀbeꢀ
aꢀminorꢀpathwayꢀinꢀtheꢀpresenceꢀofꢀaꢀsufficientꢀamountꢀofꢀCO2ꢀ
[
RhCl(dcype)]2ꢀ A,ꢀ orꢀ transmetallationꢀ ofꢀ Dꢀ andꢀ
methylaluminumꢀ speciesꢀ directlyꢀ givesꢀ RhMe(dcype)ꢀ A.ꢀ
However,ꢀ generatedꢀ Aꢀ couldꢀ beꢀ convertedꢀ toꢀ theꢀ mostꢀ
thermodynamicallyꢀ stableꢀ 1ꢀ viaꢀ furtherꢀ transmetallationꢀ
24,25
becauseꢀ ofꢀ anꢀ equilibriumꢀ betweenꢀ 1ꢀ andꢀ A.
ꢀ Inꢀ addition,ꢀ
thereꢀ isꢀ aꢀ branchꢀ inꢀ thisꢀ reaction.ꢀ Aꢀ reactsꢀ withꢀ CO2ꢀ toꢀ giveꢀ
Rh(OAc)(dcype)ꢀ Eꢀ inꢀ theꢀ sameꢀ mannerꢀ asꢀ C.ꢀ Therefore,ꢀ thisꢀ
reactionꢀprovidesꢀaꢀmixtureꢀofꢀaceticꢀacidꢀandꢀbenzoicꢀacid.
ꢀ
AlMeX2
Cy2
P
–
Al(O CMe)X2
O
O
2
Rh
Me
I
P
Cy2
becauseꢀ ofꢀ undesiredꢀ predominantꢀ carboxylationꢀ ofꢀ Rh -Meꢀ
AlClX2
species.ꢀHowever,ꢀfurtherꢀanalysisꢀrevealedꢀthatꢀthisꢀproblemꢀ
couldꢀbeꢀovercomeꢀtoꢀsomeꢀextentꢀbyꢀmechanicalꢀfactorsꢀsuchꢀ
asꢀstirringꢀrateꢀandꢀtheꢀshapeꢀofꢀtheꢀreactionꢀvessel,ꢀbecauseꢀ
–
Al(O CMe)X2
CO2
2
E
AlMeX2
I
Cy2
P
Cy2
P
undesiredꢀ carboxylationꢀ ofꢀ Rh -Meꢀ speciesꢀ couldꢀ beꢀ madeꢀ
Cl
– AlClX2
Me
slowerꢀ byꢀ controllingꢀ theꢀ concentrationꢀ ofꢀ CO2ꢀ inꢀ solution.ꢀ
Finally,ꢀ itꢀ wasꢀ foundꢀ thatꢀ theꢀ reversibleꢀ transmetallationꢀ
pathwaysꢀ toꢀ giveꢀ [RhCl(dcype)]2ꢀ 1ꢀ contributedꢀ toꢀ suppressꢀ
decompositionꢀ ofꢀ theꢀ catalyst.ꢀ Thisꢀ studyꢀ willꢀ provideꢀ aꢀ newꢀ
possibilityꢀinꢀsuchꢀC–Hꢀbondꢀfunctionalizationꢀreactionsꢀusingꢀ
alkyl-metalꢀ speciesꢀ andꢀ transitionꢀ metal-catalyzedꢀ
carboxylationꢀreactions.ꢀ
Rh
Rh
2
P
P
Cy2
Cy2
AlClX2
AlMeX2
1
– Al(O CPh)X2
– Al(O CPh)X2
A
2
2
Cy2
P
Ph
H
O
AlClX2
AlPhX2
Rh
Ph
–
P
Cy2
O
rds
CO2
D
Cy2
P
Cy2
P
Acknowledgementsꢀ
Me
Ph
Rh
Rh
H
ThisꢀresearchꢀwasꢀsupportedꢀbyꢀJSPSꢀKAKENHIꢀGrantꢀNumberꢀ
24245019ꢀandꢀanꢀACT-CꢀprogramꢀfromꢀJST.ꢀT.S.ꢀthanksꢀJSPSꢀforꢀ
aꢀfellowship.ꢀꢀ
P
P
Ph
Cy2
Cy2
Me
H
C
B
ꢀ
Schemeꢀ12ꢀꢀTotalꢀfigureꢀofꢀtheꢀcatalyticꢀcycle.ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ7ꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Pleas Ce hꢀ d eo mꢀ ni oc ta ꢀ la dS jcu i se t nꢀ mc ea rginsꢀ
Page 8 of 8
ARTICLEꢀ
JournalꢀNameꢀ
1
3 (a)ꢀ H.ꢀ Urtel,ꢀ C.ꢀ Meier,ꢀ F.ꢀ Eisenträger,ꢀ F.ꢀ RomVieewnAgreticrl,eꢀOJ.nꢀlinPe.ꢀ
Notesꢀandꢀreferencesꢀ
Joschekꢀ andꢀ P.ꢀ Hofmann,ꢀ Angew.ꢀ Chem.ꢀ Int.ꢀ Ed.,ꢀ 2001,ꢀ 40,ꢀ
DOI: 10.1039/C6SC03838G
1
Representativeꢀ reviewsꢀ onꢀ carboxylationꢀ ofꢀ organicꢀ
compounds:ꢀ(a)ꢀT.ꢀSakakura,ꢀJ.-C.ꢀChoiꢀandꢀH.ꢀYasuda,ꢀChem.ꢀ
Rev.,ꢀ2007,ꢀ 107,ꢀ2365–2387;ꢀ(b)ꢀS.ꢀN.ꢀRiduanꢀandꢀY.ꢀZhang,ꢀ
Daltonꢀ Trans.,ꢀ 2010,ꢀ 39,ꢀ 3347–3357;ꢀ (c)ꢀ M.ꢀ Cokoja,ꢀ C.ꢀ
Bruckmeier,ꢀ B.ꢀ Rieger,ꢀ W.ꢀ A.ꢀ Herrmann,ꢀ andꢀ F.ꢀ E.ꢀ Kühn,ꢀ
Angew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2011,ꢀ50,ꢀ8510–8537;ꢀ(d)ꢀK.ꢀHuang,ꢀ
C.-L.ꢀSunꢀandꢀZ.-J.ꢀShi,ꢀChem.ꢀSoc.ꢀRev.,ꢀ2011,ꢀ40,ꢀ2435–2452;ꢀ
781-784;ꢀ(b)ꢀC.ꢀWerlé,ꢀC.ꢀBailly,ꢀL.ꢀKarmazin-Brelot,ꢀX.-F.ꢀLeꢀ
Goff,ꢀM.ꢀPfefferꢀandꢀJ.-P.ꢀDjukic,ꢀAngew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2014,ꢀ
53,ꢀ 9827–9831.ꢀ Forꢀ otherꢀ 14-eletronꢀ rhodiumꢀ complexes,ꢀ
see:ꢀ(c)ꢀP.ꢀZhao,ꢀC.ꢀKrugꢀandꢀJ.ꢀF.ꢀHartwig,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.,ꢀ
2005,ꢀ127,ꢀ12066–12073;ꢀ(d)ꢀA.ꢀB.ꢀChaplin,ꢀOrganometallics,ꢀ
2014,ꢀ33,ꢀ624–626;ꢀ(e)ꢀM.ꢀT.ꢀWhited,ꢀA.ꢀJ.ꢀKosanovichꢀandꢀD.ꢀ
E.ꢀ Janzen,ꢀ Organometallics,ꢀ 2014,ꢀ 33,ꢀ 1416−1422;ꢀ (f)ꢀ M.ꢀ
Hasegawa,ꢀY.ꢀSegawa,ꢀM.ꢀYamashitaꢀandꢀK.ꢀNozaki,ꢀAngew.ꢀ
Chem.ꢀInt.ꢀEd.,ꢀ2012,ꢀ51,ꢀ6956–6960.ꢀ
(
e)ꢀZ.ꢀWenzhenꢀandꢀL.ꢀXiaobing,ꢀChin.ꢀJ.ꢀCatal.,ꢀ2012,ꢀ33,ꢀ745–
7
9
1
56;ꢀ (f)ꢀY.ꢀTsujiꢀandꢀT.ꢀFujihara,ꢀChem.ꢀCommun.,ꢀ2012,ꢀ48,ꢀ
956–9964;ꢀ(g)ꢀI.ꢀOmae,ꢀCoord.ꢀChem.ꢀRev.,ꢀ2012,ꢀ256,ꢀ1384– 14 Similarꢀ strategiesꢀ toꢀ stabilizeꢀ 14-electronꢀ complexesꢀ inꢀ
405;ꢀ(h)ꢀX.ꢀCaiꢀandꢀB.ꢀXie,ꢀSynthesis,ꢀ2013,ꢀ45,ꢀ3305–3324;ꢀ
mechanisticꢀstudies:ꢀ(a)ꢀT.ꢀHayashi,ꢀM.ꢀTakahashi,ꢀY.ꢀTakayaꢀ
andꢀ M.ꢀ Ogasawara,ꢀ J.ꢀ Am.ꢀ Chem.ꢀ Soc.,ꢀ 2002,ꢀ 124,ꢀ 5052–
5058;ꢀ(b)ꢀC.ꢀKrugꢀandꢀJ.ꢀF.ꢀHartwig,ꢀOrganometallics,ꢀ2004,ꢀ23,ꢀ
4594–4607.ꢀ
(
i)ꢀ J.ꢀ Takayaꢀ andꢀ N.ꢀ Iwasawa,ꢀ Scienceꢀ ofꢀ Synthesis,ꢀ C-1ꢀ
BuildingꢀBlocksꢀinꢀOrganicꢀSynthesis,ꢀ2014,ꢀ1,ꢀ281–307;ꢀ(j)ꢀQ.ꢀ
Liu,ꢀL.ꢀWu,ꢀR.ꢀJackstellꢀandꢀM.ꢀBeller,ꢀNat.ꢀCommun.,ꢀ2015,ꢀ6,ꢀ
5
933.ꢀꢀ
15 P.ꢀHofmann,ꢀC.ꢀMeier,ꢀW.ꢀHiller,ꢀM.ꢀHeckel,ꢀJ.ꢀRiedeꢀandꢀM.ꢀU.ꢀ
Schmidt,ꢀJ.ꢀOrganomet.ꢀChem.,ꢀ1995,ꢀ490,ꢀ51–70.ꢀ
3
16 ConsideredꢀfromꢀthisꢀstabilizationꢀeffectꢀofꢀPCy ,ꢀtheꢀroleꢀofꢀ
DMAꢀunderꢀtheꢀcatalyticꢀconditionsꢀmightꢀbeꢀsuppressionꢀofꢀ
2
3
T.ꢀ Suga,ꢀ H.ꢀ Mizuno,ꢀ J.ꢀ Takayaꢀ andꢀ N.ꢀ Iwasawa,ꢀ Chem.ꢀ
Commun.,ꢀ2014,ꢀ50,ꢀ14360–14363.ꢀ
Forꢀ catalyticꢀ C–Hꢀ bondꢀ carboxylationꢀ ofꢀ relativelyꢀ acidicꢀ
aromaticꢀ compounds,ꢀ see:ꢀ (a)ꢀ I.ꢀ I.ꢀ F.ꢀ Boogaertsꢀ andꢀ S.ꢀ P.ꢀ
Nolan,ꢀJ.ꢀAm.ꢀChem.ꢀSoc.,ꢀ2010,ꢀ132,ꢀ8858–8859;ꢀ(b)ꢀI.ꢀI.ꢀF.ꢀ
Boogaerts,ꢀG.ꢀC.ꢀFortman,ꢀM.ꢀR.ꢀL.ꢀFurst,ꢀC.ꢀS.ꢀJ.ꢀCazinꢀandꢀS.ꢀP.ꢀ
theꢀ catalystꢀ decomposition.ꢀ Presumably,ꢀ itꢀ weaklyꢀ
coordinatesꢀ toꢀ theꢀ vacantꢀ siteꢀ ofꢀ unstableꢀ 14-electronꢀ
complexes.ꢀ
Nolan,ꢀ Angew.ꢀ Chem.ꢀ Int.ꢀ Ed.,ꢀ 2010,ꢀ 49,ꢀ 8674–8677;ꢀ (c)ꢀ L.ꢀ 17 J.-C.ꢀ Choi,ꢀ andꢀ T.ꢀ Sakakura,ꢀ J.ꢀ Am.ꢀ Chem.ꢀ Soc.,ꢀ 2003,ꢀ 125,ꢀ
Zhang,ꢀJ.ꢀCheng,ꢀT.ꢀOhishiꢀandꢀZ.ꢀHou,ꢀAngew.ꢀChem.ꢀInt.ꢀEd.,ꢀ
7762–7763.ꢀ
010,ꢀ49,ꢀ8670–8673;ꢀ(d)ꢀI.ꢀI.ꢀF.ꢀBoogaertsꢀandꢀS.ꢀP.ꢀNolan,ꢀ 18 TheꢀGCꢀanalysisꢀofꢀtheꢀliquidꢀphaseꢀrevealedꢀtheꢀformationꢀofꢀ
2
Chem.ꢀ Commun.,ꢀ 2011,ꢀ 47,ꢀ 3021–3024;ꢀ (e)ꢀ H.ꢀ Inomata,ꢀ K.ꢀ
Ogata,ꢀS.ꢀFukuzawaꢀandꢀZ.ꢀHou,ꢀOrg.ꢀLett.,ꢀ2012,ꢀ14,ꢀ3986–
aꢀ veryꢀ smallꢀ amountꢀ ofꢀ tolueneꢀ (0.002ꢀ mmol,ꢀ TONꢀ =ꢀ 0.2),ꢀ
whichꢀ mightꢀ beꢀ generatedꢀ byꢀ undesiredꢀ reductiveꢀ
eliminationꢀfromꢀRh(H)(Me)(Ph)(dcype)ꢀB.ꢀ
3
989.ꢀ
4
5
AlMe1.5(OEt)1.5ꢀ wasꢀ preparedꢀ fromꢀ AlMe
3
ꢀ andꢀ 2ꢀ equiv.ꢀ ofꢀ 19 InsufficientꢀintroductionꢀofꢀCO ꢀledꢀtoꢀirreproducibleꢀresults.ꢀ
2
EtOH.ꢀ Theꢀ 1ꢀ :ꢀ 1ꢀ sharpꢀ peaksꢀ ofꢀ methylꢀ groupꢀ andꢀ ethoxyꢀ
groupꢀindicateꢀthisꢀcompositionꢀandꢀitsꢀdiscreteꢀstructure.ꢀAꢀ 20 Accordingꢀtoꢀ PꢀNMRꢀanalysis,ꢀtheꢀreactionꢀmixtureꢀincludedꢀ
SeeꢀSIꢀforꢀtheꢀpracticalꢀexperimentalꢀprocedure.ꢀ
31
tetramerꢀ structureꢀ hasꢀ beenꢀ postulatedꢀ forꢀ theꢀ relatedꢀ
compound.ꢀSee:ꢀJ.ꢀTurunen,ꢀT.ꢀT.ꢀPakkanenꢀandꢀB.ꢀLöfgren,ꢀJ.ꢀ
Mol.ꢀCatal.,ꢀ1997,ꢀ123,ꢀ35–42ꢀandꢀrefꢀ2.ꢀ
aꢀsmallꢀamountꢀofꢀRh(OAc)(dcype)ꢀEꢀatꢀlowerꢀconcentrationꢀ
3
ofꢀPCy ꢀandꢀitꢀaffectedꢀconcentrationꢀofꢀfreeꢀPCy .ꢀButꢀitꢀwasꢀ
3
trivialꢀ soꢀ thatꢀ linearꢀ correlationꢀ wasꢀ mostlyꢀ maintainedꢀ
throughoutꢀtheꢀexperiment.ꢀ
Examplesꢀ ofꢀ stoichiometricꢀ C–Hꢀ bondꢀ activationꢀ byꢀ
alkylrhodium(I)ꢀcomplexes:ꢀ(a)ꢀR.ꢀT.ꢀPrice,ꢀR.ꢀA.ꢀAndersenꢀandꢀ 21 Itꢀ shouldꢀ beꢀ notedꢀ thatꢀ weꢀ usedꢀ Chemistation™ꢀ (Tokyoꢀ
E.ꢀL.ꢀMuetterties,ꢀJ.ꢀOrganomet.ꢀChem.,ꢀ1989,ꢀ376,ꢀ407–417;ꢀ
Theꢀ intermediacyꢀ ofꢀ 14-electronꢀ alkylrhodium(I)ꢀ wasꢀ
postulated,ꢀhowever,ꢀsufficientꢀexperimentalꢀsupportsꢀwereꢀ
notꢀprovided.ꢀSee:ꢀ(b)ꢀS.ꢀE.ꢀBoyd,ꢀL.ꢀD.ꢀField,ꢀT.ꢀW.ꢀHambleyꢀ
andꢀM.ꢀG.ꢀPartridge,ꢀOrganometallics,ꢀ1993,ꢀ12,ꢀ1720–1724.ꢀꢀ
Stoichiometricꢀcarboxylationꢀofꢀarylrhodium(I)ꢀcomplexes:ꢀ(a)ꢀ
I.ꢀ S.ꢀ Kolomnikov,ꢀ A.ꢀ O.ꢀ Gusev,ꢀ T.ꢀ S.ꢀ Belopotapova,ꢀ M.ꢀ K.ꢀ
Grigoryan,ꢀT.ꢀV.ꢀLysyak,ꢀY.ꢀT.ꢀStruchkovꢀandꢀM.ꢀE.ꢀVol’pin,ꢀJ.ꢀ
Organomet.ꢀChem.,ꢀ1974,ꢀ69,ꢀC10–C12;ꢀ(b)ꢀD.ꢀJ.ꢀDarensbourg,ꢀ
Rikakikaiꢀ Co.ꢀ Ltd.)ꢀ forꢀ heatingꢀ aꢀ reactionꢀ mixtureꢀ inꢀ otherꢀ
experimentsꢀ includingꢀ Schemeꢀ 9.ꢀ Thisꢀ apparatusꢀ coolsꢀ theꢀ
systemꢀ justꢀ aboveꢀ theꢀ liquidꢀ phaseꢀ toꢀ maintainꢀ gentleꢀ
refluxing.ꢀOnꢀtheꢀotherꢀhand,ꢀexperimentsꢀinꢀTableꢀ1–3ꢀwereꢀ
carriedꢀ outꢀ inꢀ anꢀ oilꢀ bath,ꢀ whichꢀ doesꢀ notꢀ haveꢀ aꢀ coolingꢀ
systemꢀ forꢀ aꢀ practicalꢀ reason.ꢀ Suchꢀ smallꢀ differenceꢀ alsoꢀ
affectedꢀtheꢀresults.ꢀForꢀexample,ꢀTONsꢀofꢀBzOHꢀandꢀAcOHꢀ
wereꢀ 15ꢀ andꢀ 54ꢀ respectively,ꢀ whenꢀ theꢀ reactionꢀ inꢀ entryꢀ 1ꢀ
(Tableꢀ1)ꢀwasꢀcarriedꢀoutꢀusingꢀChemistation™.ꢀ
6
G.ꢀGrötsch,ꢀP.ꢀWiegreffe,ꢀandꢀA.ꢀL.ꢀRheingold,ꢀInorg.ꢀChem.,ꢀ 22 DecreaseꢀofꢀCO ꢀshouldꢀaffectꢀtheꢀresultsꢀinꢀlongerꢀreactionꢀ
2
1
987,ꢀ26,ꢀ3827–3830.ꢀ
time.ꢀ Theꢀ amountꢀ ofꢀ aceticꢀ acidꢀ inꢀ Schemeꢀ 9ꢀ (TONꢀ =ꢀ 60)ꢀ
suggestsꢀaceticꢀacidꢀdoesꢀnotꢀformꢀsoꢀmuchꢀatꢀtheꢀlaterꢀstageꢀ
ofꢀtheꢀreaction.ꢀ
7
8
L.ꢀYangꢀandꢀH.ꢀHuang,ꢀChem.ꢀRev.,ꢀ2015,ꢀ115,ꢀ3468–3517.ꢀ
H.ꢀ Mizuno,ꢀ J.ꢀ Takayaꢀ andꢀ N.ꢀ Iwasawa,ꢀ J.ꢀ Am.ꢀ Chem.ꢀ Soc.,ꢀ
2011,ꢀ133,ꢀ1251–1253.ꢀ
(a)ꢀK.ꢀGaoꢀandꢀN.ꢀYoshikai,ꢀChem.ꢀCommun.,ꢀ2012,ꢀ48,ꢀ4305–
23 Theꢀ experimentsꢀ atꢀ higherꢀ temperatureꢀ wereꢀ unsuccessfulꢀ
owingꢀtoꢀtheꢀsensitivityꢀofꢀourꢀequipment.ꢀ
9
4
2
307;ꢀ(b)ꢀK.ꢀGao,ꢀR.ꢀPairaꢀandꢀN.ꢀYoshikai,ꢀAdv.ꢀSynth.ꢀCatal.,ꢀ 24 Additionꢀ ofꢀ anꢀ appropriateꢀ ligandꢀ enablesꢀ observationꢀ ofꢀ
014,ꢀ356,ꢀ1486–1490.ꢀ
methylrhodium(I)ꢀ complexꢀ inꢀ suchꢀ Rh-Cl/Al-Meꢀ
transmetallationꢀ equilibrium.ꢀ Forꢀ example,ꢀ theꢀ reactionꢀ ofꢀ
RhCl(PCy )(dcype)ꢀFꢀwithꢀAlMe ꢀgaveꢀRhMe(PCy )(dcype)ꢀ2ꢀasꢀ
1
1
0 B.ꢀZhou,ꢀY.ꢀHuꢀandꢀC.ꢀWang,ꢀAngew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2015,ꢀ54,ꢀ
3659–13663.ꢀꢀ
1
3
3
3
1 Forꢀ additionꢀ toꢀ aldehydesꢀ usingꢀ silanesꢀ asꢀ aꢀ stoichiometricꢀ
reductant,ꢀsee:ꢀ(a)ꢀY.ꢀFukumoto,ꢀK.ꢀSawada,ꢀM.ꢀHagihara,ꢀN.ꢀ
ChataniꢀandꢀS.ꢀMurai,ꢀAngew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2002,ꢀ41,ꢀ2779–
1.5 1.5
aꢀmajorꢀproduct.ꢀInterestingly,ꢀuseꢀofꢀAlMe (OEt) ꢀresultedꢀ
inꢀ noꢀ reactionꢀ underꢀ theꢀ similarꢀ conditions.ꢀ Theseꢀ resultsꢀ
mightꢀ haveꢀ relationꢀ withꢀ theꢀ betterꢀ resultsꢀ obtainedꢀ usingꢀ
2
theꢀlatterꢀreagentꢀinꢀtheꢀcarboxylationꢀreaction. ꢀ
2
781;ꢀ(b)ꢀY.ꢀKuninobu,ꢀY.ꢀNishina,ꢀT.ꢀTakeuchiꢀandꢀK.ꢀTakai,ꢀ
Angew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2007,ꢀ46,ꢀ6518–6520;ꢀ(c)ꢀB.-J.ꢀLiꢀandꢀ
Z.-J.ꢀShi,ꢀChem.ꢀSci.,ꢀ2011,ꢀ2,ꢀ488–493.ꢀ
Cy2
P
Cy2
P
Cy2
P
5
equiv.
5 equiv.
AlMe3
Cl
PCy3
Cl
Me
1
2 (a)ꢀT.ꢀG.ꢀOstapowicz,ꢀM.ꢀHölscherꢀandꢀW.ꢀLeitner,ꢀChem.ꢀEur.ꢀ
J.,ꢀ2011,ꢀ17,ꢀ10329–10338;ꢀ(b)ꢀH.-L.ꢀQin,ꢀJ.-B.ꢀHan,ꢀJ.-H.ꢀHaoꢀ
andꢀE.ꢀA.ꢀB.ꢀKantchev,ꢀGreenꢀChem.,ꢀ2014,ꢀ16,ꢀ3224–3229;ꢀ(c)ꢀ
S.ꢀV.ꢀC.ꢀVummaleti,ꢀG.ꢀTalarico,ꢀS.ꢀP.ꢀNolan,ꢀL.ꢀCavalloꢀandꢀA.ꢀ
Poater,ꢀOrg.ꢀChem.ꢀFront.,ꢀ2016,ꢀ3,ꢀ19–23.ꢀ
Rh
Rh
Rh
2
benzene
rt, 11 h
P
Cy2
PCy3
rt, 1.5 h
P
Cy2
PCy3
P
Cy2
1
F
2
2
5 Thereꢀ wouldꢀ alsoꢀ beꢀ anꢀ equilibriumꢀ betweenꢀ 1ꢀ andꢀ
RhPh(dcype)ꢀCꢀinꢀaꢀsimilarꢀmanner.ꢀ
8
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
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