AN INVESTIGATION OF

AN INVESTIGATION OF CARBONYL INSERTION INT O M-CF

3

BONDS

By

@JAYANTHIJACOB,M.Sc.

A thesis submitted to the School of Graduate Studies in parlial fulfillment of the requirementsfor the degreeof

Master of Science

Departmentof Chemistry Faculty of Science Memorial UniversityofNewfoundlan d

July1990

St.John's Newfoundland Canada

.+.

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Abstract

Carbonylinsertionconti nues tobeofcurrentinterest a.,it playsa vita l rolein manyindustrialpreparationslikehydrcformylation,lteppe synthesis, Fischer-Tropschprocess,etc.Carbonylinsert ionhas notheen observedin M·

CF,bonds(M=transitio n metals) andthe fir,treport ofapparent carbonyl insertion in a Fe· CF,bond standsinopenconflict withbothexperimentaland theoreticalresults . Aninvestigationoftheabove report ispresentedill this thesis.

Fe(COM diars) {dlers

=

o-phenylenebis(dimethylanine))reacts withex- cess CF3Itoform the perftuoroacylFe(COh(diars)(C(O)CF3)1and theper- ftuoroalkyl Fe(CO),( diars)(CF3 l l•»m pounds invaryingyields,dependingon thereaction conditions.A high,,·,Icentration ratioof CF,Ito Fe(COh(diars) favourstheperftuoroalkylwhilea dilute solution favountheperDuoroacylcom- pound. ConcentrationVI.timeprofilesof theructio nmonitoredby19 FNMR, indicatethatthe perDuoroaikyland perfluoroacyl compound, are formedby two independentreactionpathways.The perflucroal kylisformedbyoxide- tiveadditioDofCF ,ItoFe(CO), (diars)byanonchain,freerailiCllImechanism whilethe perfluorcacylisformed by an intermolecularinsertionrueehanlsm via an ionicintermediate. The higher analoguesofCF, I formonly thepcrflu- oroalkylowingtothe greater stability of the RJradicalwhich enhancesthe rateofthefree radicalreact ion.

Twoisomersofthe perftuoroalkylcompoundwereisolatedand spcct ro- scopically identified byIH,I3C,19FNMR,lR and Massspectraascis.cisand cis.transisomers.Similarly, four isomers oft1- ""oralleylcompound were isolatedand identified. Thestruct ures ofI -croecylandoneperfluo- romethylisomerwereconfirmedby singlect~, aydata.

Contents

Abstract List ofFigures Listof Tables List of Abbreviations

viii

Acknowledgements xi

1 Introd uct ion 1

1.1 Insertion Reactions... 1

1.1.1 Int ramolecularInsertion Reactions. . 1

1.1.2 Inter molecularInsertion Reaction 4

1.2 CarbonylInsertionReactions. • . • . 4

1.2.1 Kineticsand Ratelaw... 9

1.2.2 Carbonyl Insertion in Industr y. 11

1.2.3 MolecularOrbitalStudies ofCOInsertion. 14 1.3 Absenceof COInsert ionIntoM· CF3Bonds... 19

1.4 Overview of the ResearchWork .. . 20

2 Reacti on of CFaIwith Fe(COh(dia rs) 22

2.1 Introduction ... .. .. . . ..,.. .. . . 22 2.2 Experimental. .. ... . . .... .... ... 22 2.2.1 Preparation of Fe(COM diars). . . . 24

2.2.2 ReactionofFe(COM diars) with(Fa!. 24

2.3 Results and Discussion. . . .•. •.. .. 27

2.4 SolidStateStructure.. 33

2.5 Conclusion 41

iii

3 React ionoCHigh er Ana log uesoCCF31with Fe (C O)3(di a rs) 3.1 Introd uction

3.2 Experimental .

3.3 ResultsandDiscussion. 3.3.1 IHNMR Spect ra. 3.3.2 13C NMR Spect ra 3.3.3 19FNMR Spectra 3.3.4 fRand Mass Spect ra. 3.3.5 Isomerization Study 3.4 Conclusion.

47

"

"

51 52 53 59 66 66 68 4 MechenismofCar b onylInsertionandOxidativeAdd itionin

theReactionofFe (CO M d iars ) withCF3I 15

4.1 Introduction 7a

4.2 Experimenta l.. . ...••. . . . 76

4.2.1 General... . .. ....• .. •.. 76 4.2.2 Concent rationys. TimeExperiments .... 76 4.3 Ruults. . . ...•.. ... 81

4.4 Discussion. .. ... 90

4.4.1 MechanismofCO"Insertion"intoiIFe-CF3bond 96 4.4.2 Mechanis m of OxidativeAdditionofCF31toFe(COh (diars)lO I

4.5 Conclusion. . . ... . lOa

5 Conclusio n andRecom m enda ti on References

Appendix

A Cal cul ati onoC19FShift s CorAD System s A.I Compo und:Fe(COMdiars)(C~.Fs)1.. .. A.2 Compound:Fe(COh(di,us)(C3Fr )1.. A.3 Compo und:Fe(COMdiars)(Ce F13)1

A.4 Compound:Fe( COh(diars )( CHaCF3)1. ..,. .. . . B 19FChemical Shift Tempe ra tureGradie nt Dat a C Crystallog rap hic Dat a

13 2

,as

143 143 143

'44

145 146 147 148

List of Figures

1.1 Hydroformylation... .. 11

1.2 ReppeReactions. . 12

1.3 MonsantoAceticAcid Synthesis . 13

1.4 Et hylene GlycolSynthesis 14

1.5 PolarattackofCH₃on CO group.. 16

2.1 PerfluoroalkylandPerfluoroacylIsomers. 28

2.2 IR Spectrumof16 in CH2C12 • •• 29

2.3 13CNMR Spectrumof 17 inCOCl₃ • • 30

2.4 MassSpectru mof 16 32

2.5 Mass Spectrum of21 ... ... .•... .. 34 2.6 ORTEPDrawing of theCrystalStruct ureof

cis,cis.Fe(COM diars){C(O)CF3)1(11) •..•. 36 2.7 ORT EPDrawingof theCrystal Structureof

cis,cis.Fe(COM diars){CF:s)1(21) 37

3.1 Structures ofthePerfluoroalkyl Compounds. 51 3.2 300 MHz'HNMR SpectrumofFe(COM J iars)(CH2CF3)1(27) in

CeChShowingtheAMX₃Patt ern 52

3.3 75MHz

»c

NMR Spectrumof Fe(COM diars)(C3Fr)1(24) inCDCIJ •• • •••••• ••• •• •• • ••••••• 53 3.4 75 MHzPartialIJCNMRSpectrumofFe(COh(diars)(CJF;)1in

CDCI3 •• • •• • • • • • 54

3.5 75MHzPartial¹³CNMRSpect rumofFe(COh( diars)(CJFr)124 inCOCI3 •••••••• ••• •• •• • 55 3.6 75MHzPartial¹³CNMRSpect rumofFe(COM diars)(C2Fs)123

inCOCh.. ... 56

3.7 75MHZPartial^13CNMRSpectrumofFe(COMdiars)(C6F13)125 inCOCl3 • • •• • ••.•,•• •• • • • •.• • • • • • •• ••, 57

v

3.8 15MHz13CNMRSpect rumofFe(COMdiars)(CH2CF3)127in

(Deb 58

3.9 7SMHz Partial¹³(NMR SpectrumofFe{COh( diars)(CrF1s)126

inCDCl3. 60

3.10282 MHz'⁹FNMR Spectrumof Fe(COh(diars)(C2F5)123

inCDeh .. ... . .... 61

3.11282 MHz'\IFNMR Spectrumof Fe(COh(diars)(CJF7)124 inCDCh.. ." . . .. . • •.. . . 62 3.1275MHzl9F NMR Spectr umofFe(COh(di ars)(C6FI3)125

inCDClJ •• • ••• • • • ••,•. 63

3.13 75MHz 19FNMRSpect rumofFe(COh(dim)(CH2CFJ)127

in(De h .., .. .. ..•. .. 64

3.14 75MHz19FNMR SpectrumofFe(COh(d iars)(CrFI5)126 in (Deb . .. . . .. . .... ... 65 3.15282MHz19FNMR of Fe(COh(diars)(C3Fr)124 in d,-Toluene

ShowingtheAS Spect rumatVariousTemperatures 67 4.1 Typical 75MHzl\lFNMRSpectrumfor the Concentrationvs.Time

Experiments ofEq. 4.1in C02CI2• • ••••• •••• • • 82 4.2 Partial75 MHzIIlFNMRSpect rum of CF3HResonancein C02CI2 83 4.3 300MHzIHNMRSpectrumofFe(COh( diars)andCF31Solution

Showing <.:F3HQuartet .. 8~

4.4 75 MH.:IIlFNMR Spect rumof CF3Dand CF3HinCD1Ch 85 4.5 Effect of GalvinoxylonPerfluoroacyl 88 4.6 Effect ofGalvinoxylon Perfluoroalkyl. .. 88 4.7 75MHzI'F NMR Spectraofthe Reactionof

Fe(CO}2(diars)(C(O}CF3)1withAgBF~andBu4NIin C01C12• 91 4.8 Stacked PlotofIIlFNMRSpectraof Concent ration^V5. Time

Curves(Experiment7)... 93

4.9 TheTwoIsomers of Fe·C(O)CF3•• 98

4.10The Intermolecular Nucleophilic Addition in

I

Fe(COh(diars)I]+(CF3]-• • •••• • ••••. • 100 4.11 ConcentrationY5.Time Graph for Experiment I. 107 4.12ConcentrationY5.Time Graphfor ExperimentII 109 4.13 Concentrationvs.TimeGraph for Experiment III III 4.14Concentration vs. Time GraphforExperimentIV•. 113 4.15 ConcentrationY5.Time Graphfor ExperimentV.. .. 115 4.16ConcentrationY5.TimeGraphfor Experiment VI.. 117

vii

4.17Concent rationvs.Time Graph forExperiment VII. .. 119 4.18Concent rationvs.TimeGrap~for Experiment VIII 121 4.19Concentra tionvs.Time Graph forExperimentIX . 123 4.20 Concentrationvs.limeGraph for ExperimentX.. 125 4.21 Concent rat ionvs.Time GraphforExperiment XI. 127 4.22Concent rationvs .TimeGraphfor ExperimentXII 129 4.23ConcentrationV5.Time Gra phforExperim entXIII.. 131

List of Tables

1.1 MetalCente rs forMigratoryInsert ion•. • .

1.2 Position of13( 0Label in ProductsoftheReact ionin Eq.1.7 After Floo d etal. . .. ...•.. . .•. • •. • ..,. . .

2.1 Reaction of CF31withTransition Metals, •.... . 19

2.2 Reactionof Fe(COM diats)andCFJIwithChOingein Volumeof theSoIvent.•. . . . • • . •.•••• . • • . . . .. . .. 21

2.3 CrystallographicD,naforCompou nds17and21. .•• ... .. 31

2.4 SelectedS.,ndLengt hsandBondAnglesof11and 21.... .. 32

2.5 M·eand(·F EkondDist<1ncesfromtheliterature 33 2.6 IR andElement Analysis..•. . • . . . • • . . . • ... 35

2.7 IHNMR DATA.•..•• .•.• ••• •••.• •.• • •• .. 36

2.8 IJC NMR DATA•• • . •• ••.•. ..•• • ••• • • • •.•• 37

2.9 Mu s$pectll1Dab ... •.•.•.. . ... . .. ... . . •. 38

2.10liFNMRC.'a. ..•.. .•..•..••.• .•. . ..• . •. 39

3.1 OxidativeAdditionofHigherAnalogues of CF31 41 3.2 ReactionDetlilsofHigherAnalogues• . ••. •. ... . 43

3.3 PhysicalData . 12 3.4 IHNMRSpectralData .. •.• •.• . • ... . . ..• •••. 73

3.5 13CNMRSpect ralData.. .. .. . ... . 74

3.6 l\tFNMR SpectralData.• •... ... .. . . .. ... 75

3.7 IRSpectralData. •• ..• . ... . . . 76

3.8 MassSpectralDati " ,. ,.•.. .., ,,,, , , , , ,. . 77

4.1 ExpefimenhJ Dataat_90°C - SetI•., ••,, ,,, , ,, . 80 4.2 Experiment.JIi D.JIt.JI .JIt-90"C - SetII,.• ,.• " . .. 81

4.3 Experiment.JI1 D.JIt.JI-SaIII .... . .• . . ••• • •• . . • 82 4.4 ConcentrationYI.Time DataforExperimentI.. ... . .. .. 109 4.5 Concentr.JItionVI.TimeDat.JIfor ExperimentII• • ...• III

viii

ix

4.6 Concentrati onV5,Time DataforExpe rimenttil 113 4.7 Concentra tionV5.TimeData forExpenr-ient IV 115 4.8 Concentr ation vs.Time Data for Experime nt V... 117 4.9 Concentr atio nV$,Time DataforExperime nt VI 119 4.10Concentrationvs.Time DataforExperimentVII... 121 4.11Concent ra tionV5.TimeData for Experiment VIII. 123 4.12Cf'r.centratic nV5.TimeDataforExperimentIX 125 4.13Conce nt rationV5.TimeDataforExperiment X. 127 4.14Conce nt rationvs.Time Data for Experime ntXI 129 4.15 Ccncem raric nY5 .Tir.reData for ExperimentXII• 131 4.16 Conce ntra tionvs.TimeData (orExperime nt XIII. 133 C.1 Positio nal andThermalParametersandEquivalent Isotropic Tem-

peratureFactors fer17 .. . . • . ... .. .•... 148 C.2Positional andThermal Parame tersandEquivalentIsot ropicTem-

peratureFactors for21 ... ..• •. . . ... . . 149

List of Abbreviations

CNDO

C, diars Et HFS

H OMO M O

Ph

PRDDO

HC

complete neglect ofdifferentialoverlap '1⁵-cyclopentadienyl

o-phenylenebis(dimethylarsine) ethyl

Hart ree-Fc ck-Sleter hig~estoccupied molecular orbita l molecularorbital phenyl triphenylphosphine propyl

partialretention of diatomicdifferentialmethod thinlayer chromatography

xi

ACKN OWLEDGEMENTS

Iamdeeply indebtedto my supeJ'visor,Dr. eketJablonski,for Isis invalu- able dinclion and technicaladvice during theCOUTseofth is investigation.His continuous911idanceand encouragementhas helped me immensely.

Iwould like Laextend my sinceregratitude to tke Dean

0/

Gnu/uatcStudies and tothelIcad, Departmen tofChemistryfOl'providing the financialsupport during the course of this work.

Iwould like/0thankmyhusband and my dear children,who put up with my swingingmoods andexl ended full support,

o

^{J;01l.1), OUR lORD!}

'HOW MAjESTIC IS YOU1t NAME IN AU T'HE EARTH!

WHEN I CONSIDE'1l. YOUR. 11EAVENS, T11£ WORA.': OF

youn

nNGERS, TH.E MOO N .AJ{v THE STAn s,

WHIC1t yo u HAVE SET ZN 'PlACE,

WHAT IS M.A.N THAT you A1U MINDT U l. OF 'HIM, T1f£ SON OF MAN T1fA T YOU C,41U Fon 'HIM? o l01W, OUR. J;rJ1l1),

'HOW MAjt~T1C IS YOU'll. N AM! IN All THt

£,ART'H!

[Kina L...vid'.Pulm.in TileBiblej

Chapter 1 Introduction

1.1 Insertion Reactions

The term "insertionreaction"isoften used in.. very broad co nt ext withoutmech- anisticsig nifica nce.It simp lyrelle chtheaveri llst ruct ural change wherein an unsat urat edligan dYint erposes intoametal-element,M· Xbond(d.Eq.Ll],

M-X

+

Y _ M-Y - X (1.1) Thereversereactionisreferredtoasl!liminatiQnorext rusion and unlikeoxidative addition,insertio n reaction sdonotalt ertheco ordiu t ionorthe oxidationnumber ofthe metal.TwodifferenttYPI:Sof insertionreact ionlhavebeenidentified in the literilture.namely,intramoleculu;ln d intermolecular insert ion reactions153].

1.1.1 IntramolecularInsertionRea ct ion s

Intramolecular insert ion,alsoknownas"migra toryinsertion".occurswhen both X andYare coordinatedtothe same metalcenter(d.Eq.l .2).

II - - \

"_y _ - U_y-x _ - U- y - x (\.2)

Anexternal ligandlinalIlb~quentstepoften OCtupies thesite vautedbyX.

where L

=

CO.",p.amine,halide or a basicmetal center.Dependinson the nat ureofY.these inurtion ,eact ions are further dauifiedint o two groups.The firstgroup inwhichM andXadd to the same atomof the unsat uratedligand (Y=C O,isonit riles. carbenes,ete.)isclassifiedas a 1.1insert ionruction.

x I

Y-c_

ff

U-c-x

(1.3)

The second sroup in whichMandXaddto differentatomsofthe unuturated ligand (Y=olefins••cetylen es,ete.]is classifiedasa1,2insertion reaction.

x

I

CH

"-~~ --

^(1.4)

1.4 Insertion reactions.thoughless frequelltly obse rved.havebeen reportedfor (CN),C=C(CN), (125).

H,halogen.alkyl.S, N.P01othermetals,andtheunsaturatedligandY can be C5, CO. CHO,502,50s, dienes,acetylene,acetylene.carbenes. isonit riltl, nitrO$yls. cnb enes. olefinsor organic isocyanides.The metalcentersare shownby the shaded portion of Table1.1(38.117,1251.

1.1.2 Int ermole c ul arInsert ionReacti on

Intermolecular inse rtionreactionsinvolveadirect nucleophilic.attack onthe un- saturatedligand attachedto themetalbyanexternalnucleophilicreagent.

u - Y : " x _ u-y-X

(UI

Thesereact ions occurtypicallywhenX"" Grignardreage nt,organolithium,hy.

dride. aqueous hydroxide.amines,aminoN·oxides,azideion, etc..andYis the sameasthatdescribed fortheintramolecularinsertionreactions.Seve ralfactors favoringnucleophilicadditionreactionshavebeenidentified, suchas the nucle- ophilicity of X,anetpositivecharge onthe metalcomplelC,and theCOOfdinative saturationofthe metalcom plex[53, 611.

1.2 Carbonyl Insertion Reactions

Whenthe inserting moleculeY""COfor the react ionin Eq.(1.3),the 1,1insertion isalsoknownas carbonyl inse rtion reaction.Agreat dealofwork has beenfocussed onRMn(COls systems andCOinsert ionisfoundtobe int ra molecularwit hthe alkyl groupmigrating to the ciscarbonyl group;itis stereospecific with respectto themigrating alkyl group.Theente ringligand, solventand theLewisacid added all haveaprofound effecton therate ofthecarbo nylinsert ionreaction.These featu res arediscussed below.

Carbanylatianof 1wit h13( 0gives 2 wit h13(0cistothe acylgroup [137J.

13( 0 ,therefore servesas anexterna lligandandtheinserted CO originates from

thealready coordinated COgroups therebyshowing thattheCOinsertionisin- tramolecular (cf.Eq.1.6}

DC- Y n -

r~co

CO +lJCO_

oc/ I

CO

['J

['J

(1.6)

Amor eintriguingquestio n concerning the abovesystem is whetherthealkyl group mig rates to acarbonylgroupor theCOgroupinsert s into theMn·CH3 bondtoform the acyl group.One extensively quot ed setof experimentsisthe decarhonylationof21137).ProductratiostudiesbyIR indicatealkylmigration in theMn(COMCH3 )system andnot COmigrat ion.Hewever,st udielby Floodetal.

(751demonstrate thateven thoughins~,liontakesplacehyalkyl migrationin the Mn(CO)S(CH3) system,CO migrationisalso possible for FeCp( C(O)CH2CH3)L(l

=CO.isoc~anides)depending onthesolventi1nd the incomingligand(d.Eq.1.7 )

I')

1..00_{_}...101'"'1_{o c - ...}

T/co

_l ~3

'n1f-/oCETOH[

/'L

[«, 4J

L"oo

^(1.7)

, / lolr - C O C II3

ce [,I. s}

(1,7]

Insert ion in 3wasinduced bytwoligands, CO andP( OCH2)3CCHa. The positionoftheCOlabelinthereactionprod ucts could beQ,13,10rIias shownin Eq.1.7.Anyof the struct uralpossi bilitiesshown inTable1.2is feasibledepending on the stru ctureoftheinte rmediateandthe typeofmigration.laCNMRanalysis oftheisotopiclabelintheproductswasconsistentonly wit hmet hy!migra t ion proceeding througha squarepyramidwitha basalacylgroup.

St ructureof the l

Intermediate LO P\~{';Hd~(';CH3

I

^(Ii

+11/ '

Ii

+ 71/'

~Migration:

squarepyramid 2/1 2/0/1

trigonal bipyram id

(axialacyl) 2/1 2/1/1.5

trigonal bipyramid

(radialacyl) '/1 2/0.' /0.'

CO Migration:

square pyramid all/0 2/1/ 0

trigona lbipyram id

(axialacyl) all/O 2/1 /0

trigonalbipyram id

(radialacyl) 5/1 2/0.5/0.5

stereo-randomintermediate 3/1 2/1/1

Table1.2:Positio nof13COlabel inProdu ctsofthe ReactioninEq.1.7After Flood etat,

Inthf FeCp(CO )( PPb3)Et systemshowninEq.l.8,th. configllrationofthe productcClf'rfspondsto>95% formal alkylmigr ationin nitroetha neas thesolvent whileinhexamt thyl phospho ramide(HMPA).theconfigllrationoftheprodloCt corresponds to13%formal COmigration(14J.

F,CP{CO)(PPh,)EI- F ,Cp( CO)(P Ph,)(C(O )EI) (1.8)

However,thecyclohexylisocyanideinducedreactionfOf'msproduct scorres pondins toalkylmigration in bothnitr oethane andHMPAsoJvenU.Pankowski{I'll)has propos edasimil.uCO migrat ioninst ea dofalkylmigrat ion.

Therequin ment ofa ris coordinationsitehasbeenflegantl y demon strated byHer~ngerand Brow n(91).[(CHJt:Qto(OHh h(DHz=di.u t hyl glyoxymate) reacts with

O/I.l ~~

U" c"'~ / ""c/"

u.)..,./ I ~)""

"""CH °/ ,I

[el

CO togivecompollnd8whic hon furt her treatmentwithCOdoesnotgivethe

"ylcomplex owillg tothfunf. vollrabledispositionofthealkylandtheCOgroups.

Decarbonylationofthelabelledacylcompound 9prtpared bytreati ngNaMn(CO)a withuCH3C(O)CIgives thecis alkylcompollnd10exclusively [136].Using the principltofmicroscopic revers ibility,theR grou pandtheinsfrti ngCOmustbe

mutua llycis to eacbother(d.Eq.l.9).

(1.9)

[.j

lJ

e o

I /CH3

o;~T -eo

co [IOJ

Inse rtiorlisstereospecific atthemisratinl alkylSfOUP15.29,33.73,136.lSI).

Tbisis shown inEq.1.10whereth eopticlilly activeFecompCMl ndII,underloes COinsertionwithretention ofconfiguratio n[291.

(1.10)

ueJ~

^{/ 0 PP h}

H- C- -C- -H

--J

0 "'- ~e(co;:~p

[11]

"3 C

" / 0

H- C- - C -- '

0 " "

{12] ^C

~e(CO)(PPhJ)CP

^=O

This resultsugge"ils a concerted mechanisminvolving thetra rlsitionstate13(6}.

,. _~ ] ^.

00

co I

(1.- . /1. - r

[13)

(1.11)

Themigr~t ingR group~ndtheenterin glig~ ndLhave aprofoundeffectonthe rateofCOinsertion in 1.Theratedecreaseswit h increasing elect ro nwithd rawing

~bility^{of theRgroup,and}increaseswit hincreasin~nudeophilicity^ofthe enteri ng ligand.However,this dependence ofthe rateon thenude ophilicity is notas large aswouldbeexpected for a direct nucleop hilicattack (47] .

Asseenin the reactio ns ofFeCp(C O )(PPh3)Et,solve ntplays akeyrol e in COinsertionreactions(741 .Coordinat ing solvents acceleratecarbo nylinrartion suggest ingsolve ntco-o rdination tothe metal com plex duringthe courseofthe reaction(37, 42,41,59,128,134,165.166J. Aseries ofmethylsubst it uted tetrah ydrofuran s withconstantdielectricconstant but varying donorabilityreve als thattherat e of COinsert ion inCpMo(CH3)(CO)3 increaseswith thedonor ability of thesolvent[165~.Hence,it is thedonorabriny of thesolvent which affec ts the ra teof thereactionandnotthebulk polarit y effect.Theeffect ofsolvent nudeo philicityappears to besen sitiveto the syst e minvestig~tedsincetherate of COinsertionof(Fe(CO Mlliars)( CHa)J+is indep end ent ofsolvent(1001 .Other result s indicate that the role ofnucleophilic solventistocata lyzetheformation of thecoordinatively unsat urated acylinterm ediateandnot necessarilyto stabilize it 142,1341.lewis acidsaccelerat eCOinsertionand themostprobablemechani sm involves lewisadd coordination totheoxygenofa COligandfollowtrl byalkyl migra tio n[93).

1.2.1 KineticsandRate Law

Extensive kinet icstudies (27,40.41,62.63,82 , 83 ,84,114, 136)have sugge s ted amech anism involving the reversible formationof an unsaturated16 elec t ron

10 int e rmtd iat ewhichreactswiththeextern al liga nd Lin asubseque nt step:

(1.12)

-'- '- ,-,

L

/COCH~2 I

^{/ COCHJ}

OC- - " "- -CO- OC- l.A n- CO

o~ l k-2 o~ 1

o

^CO

[' J

[14] [IS]

Thenaeueeefthe intermediilteisstill unclear.Matrix isolationand other st ud- iesindicateiiitrigonalbipyramidinte rmediate with theacyl groupinthe eqltil- toria !plane [44,98 , 129). However,uC NMRstudiesbyFloodand Jensen favo uriIsquare pyramidal intermediate withthe acylgroupin thebasal plane [45.46,71 ,81,137,167].Thereis alsosome speculationofan,,'.acyl stree, ture(33,34,43, 72.74,97,155,162 1.Also the inter mediate maybe solver t coordinat ed .sincehighlycoordinating solvents increasetherateofthe reaction I~l.

4 31 .

Mostof theCOinsertionst udieshave been performedunderconditions where thesecondste pis irreversibleLe.k_2isinsignificant(d.Eq.1.12).Applying the stea dystat e approxim:.tionto the abovemechenism, the rateofreaction beco mes

whe re.

Rate 1,1, [L I IMn(CO),(CH,l) I,H ,[L I

~1...IMn(CO),(CH, JI

k _ ktk21L)

.1,,-

k_t+k_2[L]

(1.t3)

(1.1')

11 When k2{L]isverylarge,klbecomesinsig nificant andthe equationreducesto (1.15) Howeverat low(L],therateequat ion is dependent on theligand concentration and thus reducesto

Rate =

~[Mn(COh(CH3)J

^(1.16) 1.2.2 Carbonyl Insertion in Industry

Carbonyl insertionhas gained the attentionof many researchersdue to itsextensive applicationin industrialsynthesisas outlined below.

Hydroformylation

Thehye')formylalion reaction.also known as the Oxoor Roelenreaction,con- verts olefins to aldehydesor alcohols(d.Fig.l.1)\68.1491. Sixplants currently use this processwhich involvesinsertionof olefins into a metalhydridebond,fol- lowedbycarbonyl insertion(step 3). hydrogenation (step4)to formthe aldehyde, andfurthe r hydrogenation (step 5) to form thealcoho l.

Step1 Step2

~:"p3 Step 4 Step 5

H~g~:g): (R(CH,)CH)Co(C~~:~~~'CH,CH,)Co(CO),

-""- (R(CH,)CHC(O»Co(CO),

+

(RCH,CH,C(O))Co(CO), ...!!L..,.R(CH3)CHCHO

+

RCH2CHJCHO

+

Catalyst ...!!L..,.R CH3)CHCH20H

+

RCH,CHJCH20H

Figurel.l:Hydroform ylation

12

Repp eReec t lons

In theReppesynthesis,an addend.HX,with a labile hydrogen can he added to anolefin ic:orace tylenicC·C bondwithsimultaneou s insertio n ofCO asshown in Fig.L2(23,48.68.90]. Insertion ofCO into theC· OHbondofalcohols is also possible.Mons anto usesthismet hodto synthes ize aceticacidfrom methanol [76J.

Cat alyst:HCo(CO)..

Ni(CO)...

Fe( COh

X,-OH -Q-alkyl -O-acyl -NR1 •etc, ao,otJy.t/CO

HC~CH+HX - - _HCH~CH-C(O)X c a' alyot/ CO

H~C=CH l+HX_ HCH2-CH,· qO)X

<au.l)'u/CO

CH;oX_ H3C. C(O)X

Figure1.2:ReppeReactions

Inthe Monsantoaceticacid synt hesis shown inFig.1.3.methanolis made fre rn synthesis gas (step1). Thisisconverted tomethyl iodide (step 2) which oxida tivelyaddstotherhodium catalyst(step 3).fl.rapid COinsertio noccurs (st e p3).followedbythe releaseof acetyl iodide which undergoeshydrolysisto formacetic ad d (st e p 4).

13

Step 1 CO

+

2Hz- - -- _ Step2 CH30H

+

HI----~

Step3 CH31

+

Rh..'taly't

+

CO Step4 CH3C{O)1

+

H20

Figure1.3:Monsanto Acet icAcidSynt hesis

Fiscber -TropschSynthesis

Thisisaheterogeneouslycatalyzed reactionwherethereduct ivepolymeriza- tionofCOinthepresenceofhydrogenaffordsaplethoraof products like,Q

clefins,alkanes.alcohols.aldehydes.carboxylic acids,esters andarenes [861.The productselectivity depends on many factorssuchas theCO/H2ratio,pressure, temperat ure , cata lyst.and the promoters.Thusfar.aconsensushasnotbeen reachedregarding themechanismof thereaction,however,carbonylinsertionhas beenprop osedto account forthe

c- e

bondform,1tionduringthe courseofthe catalytic reaction.

Eth yl en eGlyc ol Synt hes is

Although therearemany possiblewaystooi.~aineth yleneglycol,a direct syn- thesisfrom synthesisgasiseconomically attract ive.TheUnion Carbidemechanism ispresentedinFig. 1.4(66).

Step 1 (CO)~Co-H (COh Co-C(O)H Ste p2 (COhCo-C(O)H ....!!.a....(COhHCo-(H2CO) Ste p3 (CO)3HCo-(H2CO) (COhCo-CH20H Step4 (CO)3Co-C H~OH--C.Q...,.(COh Co-C(O)C H20H Step 5 (COJCo-C 0CH~OH--..!::!4HOCHrCH20H

+

^{cat alyst}

Figure 1.4:Eth yleneGlycol Synthesis

The majororgano meta llic speciespresentunder the react ion conditionsis HCo(CO)~ .Thereactionproceedsby int ramolecular migr2!ion of tilehydride ion from themetal to a carbonyl ligand(step 1) to form theformylligand. Analogous migration of alkylgroups to a CO ligandis obse rved but the hydridemigration is rareunder normal conditionsapparentlybecauseof thethermodynamic instabil..::

of mostmetalformylcomplexes.Step2isthe conversionof the formyl ligand to formaldehyde byhydrogenation.The formalde hydecomplexis a highly reactive species andfurther reac tionsaresimilar to those of hydroformylation.Formalde- hydeinserts into the metal-hydrogenbond to form thehydroxymethylligand(step 3)whichundergoessubsequent CO insertion(step 4) and hydrogenation (step 5) in thepresenceofCO and H2respectively to formethylene glycol.Glycerol is often formed as aside product.

1.2.3 MolecularOrbital Studies of CO Insertion

Fivedifferent molecularorbita l (MO) theorieshave been employed toexplore the reactionpathofcarbonyl insertion .Theyarebrieflyoutlined in the following sect io ns.

Ex tendedHiicke lThe ory

Thec.arbonylinsertionof Mn( CO)$(CH) won com put edalanaa reactio ncoor- dinateinwlvinafivearbitru y stepsbyHoffman(201,usins:the extendedHuckel method.Fulloptimizationofall dearees offreedomwas notceniedOYtandthe bond breakingandmakingare ontheborder line ofwhatcanbereliablytreated bythis method .Thecomputat ional result saretherefore supportedbyqualitative arguments.

As thereactionproceedsthroughthe fivesteps,C.symmetryof thecomplex ismainta inedand the cha naeinbondanglesisoptimized.Thereactionbegins wit h the migritionofthemethylgroup to thecisc.llrbonylgroupand theorbit.llls ofthe methylgroupoverlap wit hthat of the carbonyl group.Thereactionthen proceeds throua ha transition state(Step 3) totheintermediat<'! comolex (Step5), where the.lIeyl.lInionisfullyformed.Simult.llneous fotmationof.lin empty do nor orbital.m.llinlyd•• incharac ter.results in.lIdrntic decrease inenergyandhence sub ilizat ion ofthe system.

Accordinato thesecalcul.ltions.thefive coardin.llteintHmedi.Jteis .lIdistorted squarepyr.llmidand lackslow energyp.llthwaystoothersq u.lI re pyramKl.llI.trigonal bipyram idalor'1a-acyl oct ahedral isomers. Sincethemainenergy change isdue tothe metal-alkylbond,as theelectr onegativity ofthe Rgroupincreases,the orbitalene rgylevel decreasesand theR grou p becomesapoorer(1donor.This thenra isestheactiV.lI tionenergy forthe alkylmigrati on.Alkylmigrationtherefore becom esdifficult.lIStheelectronegativity of the alkylgroupincreases.The great er easeofmigrationwithi'lcreasingchainlengthisexplained asputlyduetothe elect ronegatiyityeffectand partlyduetothe decreasing bondstrengt hof the initi.lll reacb nt.Theresults also showthatalkylmigrat ion isfavouredenergetically

16 compared tocarbonylinsert ion .

Com plete Neglect ofDiffere nt ial Overlap (CND O )Met ho d Saddeiet al. used(NDDformalismto st udy CO inserti on.The reactionpathwas followedbycomputing the changesinchargedensity and bond order 11531.Since aUreaction mechanismsare explainedin termsof nucleophilicandelectrophilicpro- cesses theaut hor sclaim thatany theoreticalmet hod shouldinvolve com putiltion of chargedellsitiesandbondorders.

The chargeon the ctlrbonof meth yl group is nega t ivewhile the carbon ofthe equatorialCO group is pcsltlve. Thus,apolar attackof the CH3groupon the equato rialCO groupis favoured as shownin Fig.1.5.Itis therefore alkyl migmion andnotCOmigration whichispreferred intheMn(COMCH3 )reaction. The cha (s~at theequatoria lCOis nearly inde pendant ofthe alkylgroup.The negat ive chargeatthea carbonatomof thesubstit uentdecreasesintheorder:C2Hs>

CH3>CF H2>CF3• Hence the polar attackshouldbecom e increasingly difficult.The calc ulatio nspredicta trigoni lbipyra m idinter mediate.

-0'27 CH;--"

I

^{/ COJ ~+0·09}

OC -l.4 n - C O

0~1

CO

Figure 1.5:Polarattack ofCH3onCOgroup

Ru;z etal.[152)alsoused(NOOmethod. treati ng thepro blemin termsof bond orderarg um ent s.Themeth ylmigrat ion coordinat e was studie d by allow-

17

ing the methylgroup toleave itsoct ra hedralsite and approachaciscoo rdinat ed group ,whichfinally results inatrigonal bipyramidintermed iate. Thecourse oftt.e reaction wasdividedintosixarbih ry stages and a sequence ofsix calcu lations rep- resentingthe corrts po ndingst ructuralchanges duringthese sixst agesare worked out using(NODmet hods. Both the concertedandno ncon cert ed mechanisms wereconsideredand theenergybarrier for the concerted mechanism wasfound to be higher thanthatfor thetwostepno nconcerted mechan ism.

Abinit ioHas-tree FockMeth od

Thismeth od was used toinvestigat e carbonylinsertion in Pt(CH3)F(CO)PH3 and itwasconcluded that bothmeth ylmigrat ionandconcerte d me chanism sart ene rg~tica llyfavour~d whil~COins~rtionisnot(154).

Hertree-F ock-Slat e r (H FS) TransitionStat eMethod

Ziegler's HFS calculatio nsshow that thehighest occupied molecular orbita l(HOMO) ofthereactantMn(CO h(CH3)is themetald~2orbital.Orbitalinte racti ons are considered between theadonororbit al ofCH3and theorbitals of the Mn(COh syst e m.Asthe int erme diateforms,thed-CH3orbita l interact swith thetr"orbital ofthecis CO of Mn(COk Thisbrings considerablesta bilizatio n inenergyand Z~iglerther eforeproposedthatmethyl migrat ion is energe t icallyfavo urable1168).

Various conformation sof theint ermed iat ehave beensugge sted andtheirret- ative energiescalculat ed. An '12-intermediate struct ureisfavouredbyabout 80 kJmol-¹co m pared tothe '11.acyl at equilibrium.

18

PartialRet enti on ofDiat omi cDifferen t ial Overla p(P R D DD)Method Axe and Mary nk k usedthePRDDQmeth od(7) toobt ainthegeo metryofthe complexes involved while their energetics wereevaluat edbythe ab initioHartree Foc k theory. Thisisthefirstab initiostu dyof the completealkylmigration pathw aywit hthefirstoptimized geom etryofthetransit ionstate. Siximportant equilibrium struct ures we recom pute d.

Initially, the lone pairin theMn·CH3orbitalisdonated tothe vacant/I"anti- bon ding orbit aloftheintera cting COgroup.As themet hylgrou p migrat es the orbita lene rgy risesand the MQevolvesinto whatispredom inantly anacyloxygen

II"typelon epair orbita l.AMullikanpop ulat ionanalysis of theHOM O indica tesa

gra dua l depopulat ionofthe Mn-CH,orbit al,whichisaccompa nied bya build-up ofelect ron densit y on the carbo n acylandoxygenacyl atoms.Adramati c switc hin theorbita lcharacter tak es place inthe neighbourh ood ofthe estimatedtra nsition st ategeom etry.lewisacidsacc eleratethereac tion sincetheycoordin ate atthe acyl oxyenandlower theenergy ofthetransition state. Avac antsite;5created inthetran sition stat e duetotheluvingmethylgroup.Thesolvent can bind to the meta lat thispoint.Any kindof sta bilisatio nofthetransitionstat e should increase therate of thereaction .Hencethe rateof thereactionincre as esin polar coordinat ing solvents.

The kinet icintermediate prod uct resembl esasquare pyram idwiththe acyl groupin thebasalposit ion.In theabse nceofsolvent coordina tio n. the dihapt o structureisthe lowest ener gyproduct.

19

1.3 Absence of CO Insertion Into M -CF

3

Bonds

The absenceofCOinseetlc n intoM-CF3bondshas bee nindica tedbykinetic st ud- ies,thermodynamic:data,andmolecularorbitalstudies.In1962,Calderazzoand Cotton reportedthattherate ofcarbonylation ofRMn(CO)swithCO in2.2'·

diethoxydiethyl ether at30"Cdecreasesintheorder:

Nokinet icdata wasreportedforCH2Phand(Faas thereact ion is extr em elyslow [401.laterin1964.CalderazzoandNoackreportedthefollowingreactivity order:

(CH3)M n(COh>(FCH2)Mn (COh » (CFa)Mn(CO) r;

Insert ionisfoundto bemuchslowerfor R

=

CFH2thanCHaowhile noinsert ion isobservedforR

=

(Fa(41).In1969,King,KapoorandPannelldemonstrateda similartrend in the Cp{CO)JFe-Rsystem(106].Recently it has been shownthat theinsertionofCOinto apreformedM-R,bond is notaviableapproach(104).

The enthalpyofc:arbonylationat288K forEq.1.17

wasdete rminedand thefollowingtrend wasobserved:

Also.the Gibbsfree energy change• .6.G". remains negative for R=C(lHsandCHa while itispositive forR

=

CFaj55).Thepositive6G"indicat esthat thereact ion isnotfavourable.Thermod ynamic calculationsonothersyst ems alsoindicat e a similarcond usion(26,138].

20 MO studies support the above kineticand thermodynamicdata.Extended Hiickelcalculat io ns attribute the lackofinsertion reactivityto the strengthof the M-CF₃bond [20] while (NOD calculationsfocus on the decreasednegat ive cha rge on the a-carbon atom oftheCF3group(1531.

Axe and Marynickused PRDDO and ab initio Hartree- Fcckcalculationsto st udy the etTect sof a large setof different substituent supon the kinetic and ther- modynamicbehaviourof the group migrationreactionin the Mn(CO)sRsystem whereR=CH3 ,CH, CH3 ,CH2CH 2CH3 •CH(CH3

h,

H,CH,CeHs•~Hs.CH, F, CF2HandCF3(8].Thisstudyargues intermsof the lewisaeld-basecharact er of alkylsubstitutents.Morebasicalkylgroupstend tointeractmore favourablywith the CO21fOorbihls whileless basic alkylgroups interactto a lesser extent. This leadsto areducedtendency forelectron withdrawingalkylsto migraterelative toelectron releasingalkyls.This acid-base picture is supportedby calculations of the overlappopulations,degreesof bonding,group charges.optimized metal- alkyl bond lengths and localized molecularorbitals.Hence electron withdrawing substit uents retard the migrationwhileelectrondonatingsubstitutentsfavourit.

1.4 Overview of the Research Work

Notmany yeu s ago,the first caseof apparentCO insertion into the Fe-CF3bond wasreported (95].

Fe(COh(diar,)

+

CF31 _ Fe(COh(diar,,)(C(O)CF3)1 (1.18) Even thoughthe reaction was reported to beunaffectedby radicalscavengers, thepresumedCO insertioninto a transitionmetal perfluoroalkyl(M-RJ)~ond stands in open conflictwith both experimental and theoreticalresults.The prime objectiveof this researchworkwas to reinvestigatethereport.

21

Fe(CO h{dia rs)was treatedwitha largeexcess ofCF31 at ·78°CinCH2Ch solution.Vilriabll'yieldsQfthe perfluClfoalkyl Fe(diars)(COh(C F3)I,the perfluoroacylFe(COh(diars)(C(O)CF3)1,alongwiththe di·iodocompound Fe(COh( dius)12wereisolatedand identified.Theproductratios were determined to bea funct ion of thereac tioncond itions.The perfluoroalkylwasthe major prod uctinsoll/tionswit h high concentratio nsof CF31.while indilute$01l/t ions the perlh:oroacyl was themajorprod uct.Intermediate concent rations gave bot h the perfluoroalkyland theperfluoroacyl products.Concent ration vs.time profiles monitored atlowtemperilt ureby 19FNMRprovided evidencesuggestingthatthe apparentCOinsertionobservedin Eq.1.18occurs by intermoIeculi r insertio nand not by tileintramolec uluinsertion mechanism.The fo rmat ionoftheperfluoroalkyl com pound wufoundtobeafree radical react ion.With higheranaloguesofCF31, i.e.C~F51,n·C3F71,n·CeF.~:,n· C7Fulas wellasCF3CH~I,onlythe perfluoroalkyl com plexwas isolat ed[961.

Chapter 2

Reaction of CF ₃₁ with Fe( CO h (diars)

2.1 Introdu ct ion

CF31isknowntoru el with transitionmda lstoaffordtheproductofsimple oxidativeadditionas showninTable2.1. The gene ralmK hanismishowever notyet established.Theoxidativeadditionm.llYoccurviiac('~•certedOffree radial medtollnismil33}.In keepingwit h theoretialre5ults which prtd ictthat CO insertion intoM-RJbondisunlikely,arbonyl insertionhasnotbeenobservedin the abovereilctions.However,,t acticnofexcessof CF3'SillSwithFe(COh(d iu s) at0O(has been reportedtoformaperfluor~cylproductinsteadofthe expected simpleoxidativeadditionproduct 195).The res earchpresent ed hereo1ttemptsto rationalizethisapparentcont radict ion.

2.2 Experimental

All the experimentswereperformedin an atmosphereof dinitrogenusing standard Schlenktechniques{1571.NitrogengasWiISpurifiedbypusingthrougha series ofcolumns containingheated'De-ex'cata~st(Alph ),aetiv<IIted (4A)molecular sieves,and PtOIO'CF31

a ilS

wuused as purch sed fromAldrich ChemicalCo.

22

23

I(eage nt Product % Yield Reference

(PhP(CH,),),F.(COj, (PhP(C H,),),(CO),F.(CF,)1 (36)

Fe(CO)s (CF,)F .(CO).I 6 [107!

(EtC(CH,Oj,P),R,(CO), (EtC(CH,Oj,Pj,R,(CO),(CF,)1 (36)

(C,)Co(CO), (C,)Co(CO)(CF, )1 8 [llO!

(Cp)Rh(CO), (C,)Rh(CO)(CF,)1 60 [130!

(P(CH,) ,Ph),RhCl(CO) (P(CH,),Ph), RhCI(CO)(CF,) 1 73 [51)

(P(CH,),Phj,RhB,(CO) (P(CH,),Ph),RhB,(CO)(CF,)1 70 [51)

(Cp)I,(CO), (Cp)I,(CO)(CF,)1 40 (79)

(,'-(CH,),C.)I,(CO), (, '-(CH,j,C,)I,(CO)(CF,)1 78 [108]

I,CI(CO)(PPh,), I,CI(CO)(PPh,),(CF,)1 S7 [28}

I,CI(CO)(P( CH,)Ph,), I,CI(CO)(P(CH,)Ph,j,( CF, )1 49 (S4]

Table2.1: Reaction of CF31withTransition Metals

24

Methylene chloride wasfreshlydist illed fromPt OIOunder a nitrogen at mosphere.

Toluene wasdist illed fromsodium/benzophenoneketylunder nnrcgen .Thesam- ples werepreparedindegassedsolvents.Solution infrared spectra in (H₂0₁were recordedon a Perkin-Elmermodel·283 spectrophotometer.NMR spectrawere recorded onGE300NBor Bruker WP80 inst ruments.Mass spectrawererecorded onVG7070HSmassspectrometer.Melting pointsweTetaken inaThomas-Hoover apparatusIlsing sealed , nitrogen-filledcapillarytubesandareuncorrected.El·

ementalanalyseswere performed~,ythe Canadian Microa nalytical ServiceLt d.•

VancouverS.c. Allchromatographywas doneon aChromatronModel7924T. us- ing Silica gel adsorbent.Elementanalysis and spect raldataare recorded in Tables 2.6to 2.10.

2.2.1 Preparation of Fe (CO )a(diars)

Fe(COMd iars) wasprepared infoursteps.CHsAsl,and(CHshAsl wereprepared following themet hodof Milleretal. (131).Dimwas preparedfrom(CHshAsl followingthe methodof Nyholmetal.(139] and Fe(CO)s(dim ) was prepared fromtheabove compound usinga modification oftheliteratureprocedure (95). A highyieldof the productwasobtainedwhen thereact ionmixture washeated in a Carius tubeat180°C forseven hours.Decreasing thetemperatu re or time of the reaction resulted indecreasedyield.Thecrudeproduc.t waswashedinhexane two orthreetimes untila purelemon yellowsubstancewas obtained.

2.2.2 Rea cti on ofFe (CO h(diar s) wit h CF,l

4.5 g (0.01 moles) ofFe(COh( diars)was dissolvedin 5mLofdistilled.de- gassedCH20 , and treated wit hexcessof(Fsi gas (10 gor 0.05 moles)at

·780( .Thelemon yellowsolutioninstantlyturnedbrown and thendeep pur-

pie.Afte r2-3hours,.lin IR spect rumof the solutionsh~a domin.ntpe.k uound 1620 cm-¹puk indiatins the form.tionoftheperfluoro.Jlcyf compound ISreported earlier,On wumingthe solutionto room temper. tufethe solution turned frompurpleto brown.The reactionflukwu keptinthefreezerat-15

°Cfortwodays. r..emov.1of solvent.lindothervol.tilesfollowedbyprepare- tive thinlayerchromatography (TLC) undernitrogenwithtolueneastheeluant sep.ra te d fourproduct s.The firstband (yellow)was ide ntifiedspectrosco pically ilSci.s,trans -(diars)Fe(C(O)CF))(COhl(16),the secondband(darkyellow) as cis,cis-(diars)Fe(C(O)CF3)( COhl(17),the third band (brown)as anothercis,cis- (diars) F~C(O)CF3)(COhl(IS),andthe fourth band(pink)asthe di-icdccom- pound,cis,cis-(diars)Fe(COhl,(22).Thefirst twomajorproducts wereidentica l with thoserep orted earlier(951. Isomerizationof the two maP. acylproducts occuredwhen kept insolutionin the freezerfortwo d.ys .lind thefourth;~;mer, trans, cis (di.rs) Fe(C(O)CFs)(COhl(19),was isolatedsubse-quently.CrystalsfOf' X-raystructu reanalysis were Sfown by aslowdiffusionofhexane into a solution of the productin dichlOfometh.llne_

Theabove experimentwn reputedbyaddingexcessCFst(120ml.,20

-c,

1 atm)at -78°Cto a solution of lS(0.002moles)ofFe(COh( diars) diuol'vedin 10ml ofC H, CI,.Thesolutionwes stlrredfor2to3hours.The1620 cm-!peak, diagnost ic of theperfluDroacyl format ion,wn notobserved in theIRspect rum.

Prolonged reactionin thefreezerfor 24 to 48 hoursdid notresultinthe formation of a compund showingthe1620em- ' peak.Prep arativeTlCundernitrogen with ,.''ueneas the eluantseparat ed two products,whichwereidentified spectroscopi- c.lIy as the perfluoro.l kyl compound,cis,cis-Fe(CO),( dius)(C F3)I.nd thedi-iedc compound,Fe(CO),( diu s)12•A deanseparation could not b,.obtained.lind there wu .lways•tailingoft-, nds.TlC .nalysisoftheabovec."de S.JImple after stir-

26 ring overnight.troomtemperilll\lreshowedillnMTlCspot,which wuisoiOi ted

Toident ifythe conditionswhich determ inedtheproduct distribution.illseries of smillscaleprepa rationswuperformed.Theructionwu foilOYm1by IRspec- troscopyandthe presenceoftheperllunroacyl,\ndtheperfluoroalkylcompounds wasconfirmedby theirpeakslotabeut1600 and 1000em-IfespKtively.The resultsare presentedinTable 2.2.

Concentration Voll/meof Products Obtained ofFe;;~~3giarJ)

CI~~;2

1.17x10-¹ 5.00 M·CFs 2.35x10-¹ 2.SO M·CFs 5.87x10-¹ 1.00 M·CFsudM.C{O)eFs 1.17x10-² 0.50 M·CFsudM·CIOKFs 2.35x10-² 0.25 M·CFsand "".((OleFs 5.87x 10-² 0.10 O"~M·C(OICF,

Nosolvent M·CF,ODdM·C(OICF, M·CF,~Fo(CO),(dl",)(CF,)I;M·C(O)CF,~Fo(CO),(d;",)(C(O)CF,)1

Fe(COMdiars)

=

250mg (5.87x10-⁴moles) CF31:::::20 mlat20~C/lat m.(8.93x10-⁴moles)

Table 2.2:React ion ofFe(COh(diars) andCF31withChange inVolume ofthe Solvent

27

2.3 Results and Discussion

Fourgeometrical isomers arepossible for anoctahedralcompoundof the type Malblcd.Allhave bunisolatedandebarecte.",t ed forthe perfluoroacy lcompou nd whileonlytwoiso m ers were characterizedforthe perfl uoroalkylcompound. The s e are showninFig.2.1.

Perfluoeoacyl Is omer s

Isomer 16 has a verticalplaneof symmetryandhencelHNMR showstwo As.CH,resonances(Table2.7).Carbon-13NMRshowssix resonances attributable totwo As·CH3•threeAs-C6H4 ,andone CO.ThetwocarbonatomsinC{O)CF3are coupled to fluorine and hence twoquartetsartobserved.Thequartet at256ppm

e

J"'"29.5Hz)is assignedtoC(OleF;,and the quarte tat 113ppm

p

J=303Hz) to

qOlCF ,.

The19Fspect rumshowsa singlet dueto the CF,group.TheIR spectrumshows two strong CO peaksduetomut ually cisCO groupsand anothe r CO peakdueto theperfluoroacylgroup.St rongC-Fstretches artseenat 1230, 1180,1125 cm-¹(see Fig.2.2).

Isome rs 17 and18 lacksymmet ryplanes andshow spectral futuresas ex- plained be low.The 'HNMRspect rum shows four As-CH3lines.Thel3CNMR spect rumof 17,showninFig. 2.3,showsfourAs-CHatfive As-Ce

.1

4(oneof which is degenerate),two COresonances andtwo quartetsdueto the two carbon atoms oftheC(O)CF3group which are co up ledwithfluorine. Oneofthe two terminal COreso nan ces shows furt he runresolvedcoup lingswhic hmaybe due to a four bondcouplingwiththe 19Fnucleiof the acylgro up(4JCF==4Hz).The19F NMR spectrum she ws a sing letdue tothe CF3group.TheIRspectr umshows two terminalcarbonylpeaks andone CO peakdue to C(O)CF₃alongwithstrongC-F

co I/co

A'- F ' e _ R

I~'/I

^f

I ci',ci, Fe(CO}2 (diQ-rs) R I R,CFJ[211.COCFJ [17l R'.''''Ft(CO)2(diar, )1

2[22]

"

A' - Fe - _ co

I/co

Z.· /I

ci' ,tran,te(CO)2(diar,)R,r R,CF3(20).COCF_J[16)

co I/co

(//'- '

"

ei',ci,Fe(CO) 2 (diar, )R f' Rj'COCF

J[^18]

CO

1 / ',

A . ' _F o _ /

Z.·/I

co

trans,ci,Fe(CO)2(diar,) R1 R,-COCF

J[1 9] f

Figure 2.1: Perfluoro;lIkyl .nd PerfluOfOlc.y1 Isomers

29

30

.13C NMRof17inCDCI3 Figure2.3.

31

stretches.Isomers17.lind18 show similarspectral featu res.X- ray crystaUogrOllphy wu used to distinlu ishthe isomers.lindto confirmthestructure of17.Isomer 19has a horizontalplane of symmetry andand itsIH NMR spectrumshows only twoAs<-CH,lines.The IR spec tr um shows one slronS..ndoneweak .lIbsorpt ion consistent withmutually trans COgroups,andanotherCOpu kdueto C(O)CF3• Themassspect ralfragmentuionpatternofcom pounds16and 17isgivenin Table 2.9. In general. the mass spectraoffluorocarbonderivativesoftransition met als disp lay seq uential loss ofcarbo nylspresent followedbyelimin at ionofneutul metalfluorides.HF.CF"CF,(Fs.and Fatoms(121).Compounds 16 and 17 showextrusionofCFifollowedby sequentialloss ofthethree carbonyls(d.Fig.

2.4).Thepukheightof M+·. CF3fot16is39.08%ofthe base height while that of M+··COis only0.88%of thebase height.Heeever,thepeak Jt488 whichis due to therearrangement of .afluorine Jtomfromthe CF:sligandtothemeta!ion isJbundJnt(39.05% base height).Thissuggests thtsequentiJlloss ofcu bonyls which must beincom petitton withthe process ludingtoelimination ofthe CFi fragmenthas Jlso ccccred.

Per fluor oalkyl homers

Isome r21, like17and 18lacks a symmetryplaneandshowsthesame spect rJI pJttern asthe acylisomers,Isomer 20 has symmetryeleme nts similar tothe perlluoroacyfisomer16 Jndshows asim ilarspectral pau em(d.Tables2.6t02.9).

However,thefragmentation pattern in themllSs spect rum isdifferent . Sequential loss ofcarbonyls is not seen andinstead two COgroupsare lost sim ult aneously followed bythe rearrangementof.a fluorineatom from the CF:sligand tothe metal ion.Hencethe CF2group is eliminate dgivingthe488peak which thenIou s a fluorineatomgiving the469pe.ak(d.Fig.2.5).SuchJrearrangemen t hasbeen

:

.

+, :- b~

"

+~ .

:--= _:

~

. .

^~

;;-

.

"

~ :

f - - - -

.. . _{. :}

. .

- . . - .

^"

. :

~

-

^{d ~}

:1'2

33

reported in awiderangeof fluorocarbons[121].

Fe( C Oh (di.arl)I :z

Th edi-icdccompound (1351 22is formed alo ngwiththeperfluoroalkylandthe perfluorcacylcompo unds.Its NMRandIRspect ra show a spect ral pattern similar tothoseof theperfluoroacylisomers17and 18 and hencecis,cis geome t ry was assigned (see Tables2.6to 2.9).

Thesmallscale experimentsdone to,,'entify the co nditionswhichfavourthe acylandthealkylproductsindicatedthat whe nthequantities of thereactants Fe(COh(diars)and CF₃₁areconstant, ahighlyconcent ratedsolut ionfavoursthe perfluoroacylasthemajorprodu ctwhileadilute solutionfavoursthe perfluoroalkyl u the majorproduct.Intermediateconcentra tio ns resul tedinrheforma tionof boththeac.ylandalkylprod ucts,Reaction in thesolid state alsoafford ed both thealkyland theacylproduct s.

2.4 Solid State Structure

Crys ta lstruc t ures were obtain ed forseveralproductsinorder toconfir m their structuresand geometr ies.ORTEP drawings of cis,cis-Fe(COh(di ars)(C{O)CF3)1 17andcis,cis.Fe(COh(diars)(CF3)121 areshowninFigs_2.6 and2.7resp ectively.

Asummaryofcrystal datafor17and21 is giveninTable 2.3 .Selected bond lengthsandbondangles arelisted inTable2.4.¹Int e nsitydatawascollected on aNonius diffractom eter at295KusingthefJ/2(Jscantechniq uewit hprofile analysisata scanspeed of4° /min.Threesta ndards were measuredafterevery 100reflectionsand nosignificantcryst a l decaywasdetected.Spacesrou ps were ITheRnalatom k pos itional plLfameler8andtheeq u ivalentiaotropielemperll.\uferattors are Ii:iltedinAppendilt C .

35

det erminedbysyst e matic absences.Unit cell parameters for17wereobtainedby le as t squar esrefinementof the settinganglesfor22 reflections(40⁰:s;26:s;44.8° ) andfor21,30reflec.tions (40⁰:528::545").Correo:tions weremad e for absorptio n.

The structureswere solved usingdirect methods (MULTAN)plus a differ- enc eFourier mapand refine dbyfullmatriKlea st-squares withcountingstatistics weights. j-l-atcmpositions werecalculatedbut theirparam eterswere not re- fined.The(·Hdefault distancewas setat 1.08A.All heavier atomswererefined aniso tropica llyfor 17, andfor 21,only I,As,and

r

~weredone.The C2and C9 carbonatoms of21 are the reforeseenas disto rtedellipsoids.Therefinement of 21 ;snot satisfactoryas suggestedbythedifferencebet ween Rand Rw•unusual C-Fdistanc es, andtheresidualelectr o n density. The st ructureis beingresolved using~disorderedmo delfo rthe CF3group~Allcalculations wer e performedwith the NRCVA>..Crystal Struct ure progra m sl78J.Scattering facto rs weretaken from the Interna t io naltables for X-raycrysta llograp hy194].

The structurtSofboth17 and21 describe a slightlydistorte doctahed ro nwit h a

cls.ee

geometl)' thereby confirmingthe assignm ent madeby spectrosco py.In b-at hthese co mpound s,ano ma louslylargethermalfactors werefoundaro u ndFe- C(2)-O(2}(17)andF~CF3(21)andreliablebonddistances/anglescould not be made fOfthesegroups.III17,tht~e-C(O)bondis 2.05A, which isin agreemen t wit h there po rted va lueof 2.00A 1104).The averageC-Fbend distanceis 1.375 A and agre eswell with the lit erat ure valueshown inTa ble 2.5,TheFe- C(l)O bondlengthis1.73A as expected .

'E.Glbe,NRC Chrrni-nyDiYieioll, OUI...., OMario.

36

Figure 2.7: ORTEP Orawina of the Cryshl Structu re of cis,cis·

Fe(COh{ diOl rs)(CF3)1(21)

~

38

Crysta ldata Fe(CO Mdiars)(CF3)1F. (COj,(d l.,,)(C( O)CF,)1

21 17

Empiriea!formula Ct3H16As2F3FelO2 CHH16AslF3FelO3

Molecular weight 577.73 621.86

Cry st al dimension(mm) 0.10xO.10)( 0.30 0.20x 0.40x 0.40

Cry stal system Orthorhombic Monoclinic

Space group Pca b P2,

.(Al 13.9062 (8) 9.1 8~ (4 )

b(Al 16.0694 (6) 8.987(4)

,(Al 17.1146(8) 12.175(4)

V(A') 3824.50 986.55

~ 100.930(20)

Z(m oleculesjceU) 8 2

F(0 0 0)elec t ro ns 2255.53 579.88

Dc<>Icd(Mg!r.•3) 2.007 2.093

jJ( m m-1) 5.84 5.61

;(AO) 0.70'30 0.70930

29(m,,)(d. g ) 44.8 44.8

No.reflect io ns measured 4066 1379

No.uniquereflections 2458 1378

No.uniquerefl.In.,>ocr(1".,) 1725(0= 2.5) 1185( n::::2.5) lastleastsq.cyclec a lcd.wit h 38atoms 40atoms

195paramet ers 141 paramf!ter s 1725refls. 1185 refle.

R,(sig.refi.} 0.072 0.071

R",(sig. refl.] 0.04' 0.081

Goodnessoffit 5.115 2.031

RJ(all refl.) 0.106 0.084

R...(allrefl.) 0.049 0.091

Max.shih/u

o .m

0.191

last D-map :

deepesthole.e/A3 ·1.670 ~1.210

highestpeak.

e/A 3

2.920 1.770

Transmissionfactors 0.408956 0.318862

'0 '0

0.554139 0.492092

Table2.3:Crystallogra.phic DataforCompounds17and21

39

Bond

I

F.(COh(d;,.,)(CF,)1 (21 ) F.(COh(dl. ,,)(C(O)CF,)1(IT) bondlengthsinA

fe-I 2.654(3) 2.637(5)

Fe-As(l ) 2.357(3) 2.354(5)

F.-A' (2) 2.350(3) 2.367(7)

F~C(I) 1.842(24) 1.730 (4)

F.-C(2) 1.670(3) 2.080(5)

F~C(3) 2.210 2.050 (3)

C(I)-O(I ) 1.070(3) 1.120(5)

C(2).O(2 ) 1.180(') 0.620( 5)

C(3)·O(3) 1.210(4)

C(3t')-F( I ) 0.940(3) 1.400( 5 ) C(3t')·F( 2 ) 0.990(3) 1.350(4)

C(3t4)-F(3) 1.080(3) 1.400( 4)

Bondanglesin degrees As(1)·Fe-As(2) 84.78(11) 185.96(20) As(l )·Fe-1 87.71(12) 92.94(19)

I·F~C(3) 87.00(9)

C(3).F~C( I)

194 .00

( 14)

C(2)-F~A,(2) 91.00(9) 88.60(12)

I- F~C(2) 178.1(9) 178.50(12)

A,(I)·F~C(I) 173.4(7) 176.80(10)

Cril:F~A,i2i 174.8(91

Table 2.4:SelectedBondLengthsandBond Anglesof17 and'21

Table2.5:M-eand(-FBondDistancesfromtheliterature

Compo und Bond dC_Fin

A

Bond dM _ C'in A 1I'·C5HsRh(CO)(C2F:;)1 (·F 1.310 Rh·C F2 2.080 ((F,l M"((Oj, (-F 1.370 Mn-CF3 2.056 cis·(HF,CCF2hFe(CO)~ (-F 1.379 Fe-CF2 2.068

transIt Ionmeta

40

41

Thetra ns influe nc eof subst itutedace ty l gro u pshilS beenIo.ud ie d andis shown todecreaseinthe series(28J:

((O)CH,>C(O)CH,F>C(O)CHF,>C(O)CF, Acco rdingly, theFe.As(l)andFe-As(2)donotshowanydifferencein theirbond lengt hs.TheaxialFe-C(2}bondin21is shorter thantheequatorialFe-C(l)bond.

Asimilarobservation has been (<<tnlly reporte J forfou r f!uoro-o rgano metalli c com pounds ll04].TheFe-C(3)bondleng t h couldnotbecorrectly assigned owing tolar ge therma lfacto rs aroundit.TheFe-C(perfluoroalkyl) bondleng thsreport ed inlite ratu reare given in Table 2.5.Fromthe 13CNMR analysis.itappear sthat Fe-C (perfluoroalkyl)bondis longertha ntheFe-C(O) (pe rfluoroacyl)bond.The 13C_1IlF couplingconstantin 17 is 302Hz,whilethatin 21is360Hz .Hence,the C·F bond is stronger in21 therebyindicating that theFe-C (perfluoroa lkyl) bond is weaker thanthe Fe-C(O)(perfl uroacyl}.The tra ns influence of theCF,group isshown to decreasein theseries [28]:

CHa>CHF,~CH~F>CF,

The Fe-As(l )and Fe- As(2)bond lengthsare ofsimilarmagnitud etotho se of 11.

2.5 Co n cl u s io n

Dependi ngon thereaction conditions,Fe(COh(diars)reactswith(F3ltoform theperfluoroacyland/ o r theperfluoroalkylcompounds .Fourisomers o,f theform er andtwoiS~·T1ersofthelatterwereobtainedand characre rizedusingspectrosc opic andsingle crysta lX-ray data.Theparameterscont rollingt~.eproductdistribut ion were investigatedandtheresult sare presentedin Chapt er4.

Elem ent.1IAn~lysis JR-inern"

Compound M.P. .".~r n .".Hydro&en

.l.~'u~te oundIl.~cul~t~ Fccnd ",0 tr.ocf', ",F.

cis.tr~ns-Fe{(OMdjus)(C{O)CF3)J(16) 182.0 27.04 21.13 2.59 2.24 1975 1620 1230.1180.1125 2010

cis,cis-Fe(COh(diars)(C(O)CF₃₎1(17) 157.5 21.04 21.45 2.59 2.55 1960 1630 1230.1180.1125 2010

cls,cis·Fe(COM diafs){C{0 )CF3)1(18) 1970 1605 1220.1180,1115

2010

tf~ns,cis-Fe(COh(diars)(C(O)CF3)119) 1975 1600 1220,1180,1120

2010

cis.t,~ns-Fe(COMdiars)(CFJ)1(20) 171.5 26.29 26.45 2.72 2.79 1980 · 1080.990

2010

cis,cis·Fe{tOMdiars)(CF3) '(21) 170 26.29 25.91 2.12 2.73 1970 • 1050,990 2010

,is,cis·Ft(COh( diars)11(22) 1960 •

2010-

~::::inCH1ClJ;Elemental~nalysjsand M.P.of18~nd10werenotobtainedsincethesewere onlyminor products.

Table 2.6:IRand£tementAnalysis

~

43

Compound As·CHa o-C"H.

cis,t rans-Fe(COh( diiHS)(CCO)CF3)1(16) 1.62, 2.07 7.70(m)

cis,cis-Fe(COh(diars)(C(O)CF3)1(1'l) 2.23,2.02, 1.77,1.65 7.68 (m)

ds.eis-Fe(COh(diars)(C(O)CFa)1(18) 1.66.1.74.1.90,2.06 7.58 (m)

trans,cis-Fe(COh(diars )(CCO)CFa)1(19) 1.89,1.69 7.67 (m)

cis,cis.Fe(COh(diars)(CFa)1(21) 2.21,2.09,1.76,1.62 7.71(m )

ds,t rans-Fe(COh(diars)(CFa)!(20) 2.14,1.77 7.70(m)

cis.cis.Fe(COh(diars)h(22) 2.47,2.10. 1.95. 1.62 7.78(m)

Solvent:CDCh;Reference Compound:Me. Si Shiftvaluesin ppm

TaMe 2.7:IHNMR DATA

is :<l

~

;!;

~ :5 3

"'

^~;j

i ^~g _{~~~ ~}

^o:f~

"'

~

::

^::l

~ ~5 5a;g

~

; ;3~

^~~

a;a ; ^{; ;;;}

~

!:i:<i

~~

~

~

_ N

b ;::a

~g

J!. ~ ~ ~ ~

~ ~

~ '"

~ ₈ ^~; _{E ~} ^~~ _{~ ~}

.!I 2-

c,

~ ~

~ ^-"'

^~

^iQ

^~

~

^{II ~~}

^'"

^<';~~

^" ,

e,

;:

8 _~

^{::J~ -;;}

_;J ~i ^{~ ...}

J.

^{N NN ...}

!-

~

.:: _~

~

~

g. _~

r

^{<::I ><}

IE

I ^~;:-

^.~

_~"

~ =

^:;'2

E

i '::' _8'

^!.~

.s _{:: ~} -" 8

i ⁸

i · s

~-

^:F

^.!.

^:F '5.

· 5 · 5

·5

.~ ·5

:c

~

e, ti.

&:>

&.

~ ~

§

"

.a •

"

45

Compound _'R,

cis,trans-Fe(COh{diars)(C(O)CFa)1(16) -79.4

c.is,cis-Fe(COh(diars)(C(O)CFa)1(17) -78.&

cis,trans-Fe{COM diars)(CFa)1(20 ) +12.9

cis.cis-Fe(COh(diars)(CFa)1(2 1) +10.8

Solvent:CDC!a;Referencecompound:CFCI, Shiftvalues in ppm

Table2.10: IIIFN~IRData

46

Chapter 3

Reaction of Higher Analogues of CF _3I with Fe(COh(diars)

3.1 Introduct ion

AsdiscussedinChaplet'2.transition metal complexesareknowntoundergooxida- tive ildditionreactions with perllooroalkyl iodides.limite dexam ples art known for thehigheranaloguesofCF,I•.lISshowninrable3.1.Fe{COh(diars}reactswith the higheran;r,log ues of CF,I,nilmely.C2F~l.n·~F,I.n·CeFI:JI,n-CfFulas well "

CF3CH21toyiefd the corresponding oxid<lltivei1dditionproduct.Fe(COh{diars)R/I.

in good yield.Theseresultsareinte restingsinceinthe Fe(CO)3l ,series. oxidative additionhilSnotbeen observedfor.alkyliodides other thanCH31.Stenehinderanee hn been5uuestedtoi1ccountfor these results 1144].However, oxidat ive addi.- tionofgroupslaf&erthan CH3•is bcilewhenacarbonylligandintheFe(COhl, seriesissubstitut edbylabile liga ndssuc htISN₂(24 ,25) orCH₃CN [43).Also,in cont rast to CF₃1.thehigher ollnalog ues donot formthe perfluoroacylcompound in any significantyield.

.7

Reagent

Rt'

Product Reference

F.(CO). C2Fsi F.(CO).(C,F.)I (124)

(3Frl F.(CO).(C,F,)I (124) C1Fui Fe(COMCrF1s)1 (109)

trans-Fe(COh( CaHsh (3F7! No reaction [123) PC2Hs

h

cis·Fe(COh(diphos) (3F71 Fe(COh(diphos)(C3F1)1 (123)

'll"CsHsCo(COh C2Fsi 'll'CsHsCo(CO){C2Fs)1 111O) 4F71 1fCsHsCo(CO)(C3Fr)1 (11O)

Table3.1:Oxidativ eAddition of HigherAnaloguesof CFal 48

3.2 Experimental

purc.haHdfrom Ald rich.n·C,fl$ lshowedtracesofiodineandhenceWiI Sstirred withmercuryovernightilnddisti lled.

The methodology foltowed is same asthat describedinChilpte r2. 424 mg (0.99x10-³moles) ofFe(COh(diars) wasdissolved in 5 mLofdichtcrc rnethane and 50 ml (2.2x10-'moles)ofC~Fslwnsyringed intothesolutionat-78 0(.The yellowsolution turnedbrownimmediatelyilnditwasstirred for 2 hours 011-78

0 c.

Removal ofsolventilndothervolatilesunder vacuum gavea reddish brow nFrodul.'~·":-:hwasiselat edil5iIbrown·bimdon pre pu iltivethinlayer chrc- milltography withtolueneIStheelutant, Thiswaside nt ified spect rosco pically as cis,cis·Fe{COhCdi;us)(C2F.)1. A thinpinkbandwhichalso ilcco m ptlnied the above product wui50lated andidentified byspKtrOKCpyillthedi-iodo com- pound 22,which wu lllso obuinedinthe rellct ions of CF,,1.The rellctions of Fe(CO h(dius} withotherR,Icom pounds weresimilu to thatofC2Fsiilndthe detilils ilreshowninTable3.2. SinceitWilSobserved inthecue ofCF31that a conce nt rated reilctionmixturebvoured perflUOfoilcyl fOfm,ation,there4lct ions of the higher ,an,alogues wete curiedout withjustsuffidentsolvent todissolve the Fe(CO),,(dius) (0.5mL).Only verysmallperfluOfoacylpeakswere observedinthe IR spectra ,and noperlluoroacylderivatives could be isolated.

~ ~ ;

^~

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^-e

_~ ^l ~ _~

:r :r :r ; :r s _{:~ :~.}

^e

s

5' · 5 '5

.. _{~ ~ .. .. ..}

~

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0_

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_{~ ~}

..

^~ ill ^!l

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^{-s, ."}

~

~ .:J ^,;:J U^,;:

?~ 2' 2' 2' i' 2'

E E E

,

E

o.s o _{~ E}

~ ^{~ lG}

":;S:'o e,

e e

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r 'f

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