Silica-functionalized N-propylpiperazine for immobilization of palladium nanoparticles as efficient heterogeneous catalyst for cyanation reactions

Article abstract of DOI:10.1016/S1872-2067(12)60532-4

An efficient heterogeneous Pd catalytic system has been developed, based on immobilization of Pd nanoparticles (PNPs) on a silica-bonded N-propylpiperazine (SBNPP) substrate. The SBNPP substrate effectively stabilizes the PNPs and improves their stability against aggregation. The catalytic activity of this catalyst was investigated in the cyanation of aryl halides with K ₄[Fe(CN)₆] as the cyanide source. The catalyst could be recycled several times without appreciable loss of catalytic activity.

Full text of DOI:10.1016/S1872-2067(12)60532-4

ChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ718–722
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
ava i l a b l e a t w w w. s c i e n c ed i r e c t . c o m
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j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e /c h n j c
ꢀ
ꢀ
Article
Silica‐functionalizedꢀN‐propylpiperazineꢀforꢀimmobilizationꢀ ꢀ
ofꢀpalladiumꢀnanoparticlesꢀasꢀefficientꢀheterogeneousꢀcatalystꢀforꢀ
cyanationꢀreactionsꢀ
ꢀ
KhodabakhshꢀNIKNAM*,ꢀAbdollahꢀDERIS,ꢀFarhadꢀPANAHI
ꢀ
DepartmentꢀofꢀChemistry,ꢀFacultyꢀofꢀSciences,ꢀPersianꢀGulfꢀUniversity,ꢀBushehrꢀ75169,ꢀIranꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
AnꢀefficientꢀheterogeneousꢀPdꢀcatalyticꢀsystemꢀhasꢀbeenꢀdeveloped,ꢀbasedꢀonꢀimmobilizationꢀofꢀPdꢀ
nanoparticlesꢀ(PNPs)ꢀonꢀ aꢀ silica‐bondedꢀ N‐propylpiperazineꢀ (SBNPP)ꢀ substrate.ꢀTheꢀ SBNPPꢀsub‐
strateꢀeffectivelyꢀstabilizesꢀtheꢀPNPsꢀandꢀimprovesꢀtheirꢀstabilityꢀagainstꢀaggregation.ꢀTheꢀcatalyticꢀ
Receivedꢀ30ꢀSeptemberꢀ2012ꢀ
Acceptedꢀ18ꢀDecemberꢀ2012ꢀ
Publishedꢀ20ꢀAprilꢀ2013ꢀ
activityꢀofꢀ thisꢀcatalystꢀ wasꢀinvestigatedꢀinꢀ theꢀcyanationꢀofꢀ arylꢀ halidesꢀ withꢀK
4
[Fe(CN) ]ꢀasꢀtheꢀ
6
cyanideꢀsource.ꢀTheꢀcatalystꢀcouldꢀbeꢀrecycledꢀseveralꢀtimesꢀwithoutꢀappreciableꢀlossꢀofꢀcatalyticꢀ
activity.ꢀ
Keywords:ꢀ
©ꢀ2013,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
Palladiumꢀnanoparticleꢀ
Silica‐bondedꢀN‐propylpiperazineꢀ
Cyanationꢀreactionꢀ
Arylꢀhalide
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1.ꢀ ꢀ Introductionꢀ
liberatesꢀ highlyꢀ poisonousꢀ hydrogenꢀ cyanide.ꢀ Recently,ꢀ anꢀ at‐
tractiveꢀimprovementꢀwasꢀmadeꢀbyꢀBellerꢀandꢀcoworkersꢀ[8,9].ꢀ
Arylꢀ nitrilesꢀ areꢀ importantꢀ buildingꢀ blocksꢀ ofꢀ numerousꢀ
Nontoxic,ꢀinexpensive,ꢀandꢀeasilyꢀhandledꢀK
4
[Fe(CN) ]ꢀwas,ꢀforꢀ
6
pharmaceuticals,ꢀ agrochemicals,ꢀ herbicides,ꢀ naturalꢀ products,ꢀ
andꢀdyesꢀ[1,2].ꢀTheyꢀareꢀalsoꢀvaluableꢀintermediatesꢀinꢀorganicꢀ
synthesisꢀandꢀcanꢀbeꢀeasilyꢀtransformedꢀintoꢀaꢀrangeꢀofꢀhetero‐
cycles.ꢀInꢀ addition,ꢀnitrilesꢀareꢀ versatileꢀintermediatesꢀinꢀ syn‐
theticꢀorganicꢀchemistry,ꢀsinceꢀtheyꢀcanꢀbeꢀeasilyꢀconvertedꢀintoꢀ
compoundsꢀ withꢀ otherꢀ functionalꢀ groupsꢀ suchꢀ asꢀ carboxylicꢀ
acids,ꢀ amides,ꢀ amines,ꢀ andꢀ aldehydesꢀ [3].ꢀ NaCNꢀ andꢀ KCNꢀ areꢀ
generallyꢀ usedꢀ asꢀ theꢀ cyanatingꢀ agentsꢀ forꢀ cyanationꢀ ofꢀ alkylꢀ
halidesꢀ[4].ꢀHowever,ꢀtheꢀextremelyꢀpoisonousꢀnatureꢀofꢀtheseꢀ
cyanideꢀsaltsꢀseriouslyꢀrestrictsꢀtheirꢀapplicationꢀfromꢀtheꢀen‐
vironmentalꢀ perspective.ꢀ Recently,ꢀ severalꢀ methodsꢀ forꢀ theꢀ
cyanationꢀ ofꢀ alkylꢀ halidesꢀ usingꢀ trimethylsilylꢀ cyanideꢀ
theꢀfirstꢀtime,ꢀintroducedꢀasꢀaꢀcyanideꢀsourceꢀinꢀcyanationꢀreac‐
tionsꢀ [8–10].ꢀ Furtherꢀ modificationsꢀ ofꢀ theꢀ protocolꢀ wereꢀ re‐
portedꢀforꢀPd‐ꢀandꢀCu‐catalyzedꢀcyanationꢀofꢀarylꢀhalidesꢀwithꢀ
4 6
K [Fe(CN) ]ꢀ[11–21].ꢀ ꢀ
Inꢀrecentꢀyears,ꢀconsiderableꢀattentionꢀhasꢀbeenꢀpaidꢀtoꢀtheꢀ
preparationꢀofꢀ heterogeneousꢀ Pdꢀcatalystsꢀ basedꢀonꢀnanome‐
ter‐scaleꢀPdꢀspeciesꢀ[22,23].ꢀPdꢀnanoparticlesꢀ(PNPs)ꢀonꢀaꢀsuit‐
ableꢀ supportꢀ areꢀ recoverable,ꢀ ligand‐free,ꢀ greenꢀ catalyticꢀ sys‐
temsꢀwithꢀimprovedꢀcatalyticꢀpropertiesꢀ[24–31].ꢀInꢀheteroge‐
neousꢀPNPꢀsystems,ꢀtheꢀcatalyticꢀpropertiesꢀareꢀimprovedꢀasꢀaꢀ
resultꢀofꢀtheꢀhighꢀsurface‐to‐volumeꢀratio,ꢀandꢀconsequentlyꢀtheꢀ
largeꢀfractionꢀofꢀmetalꢀatomsꢀatꢀtheꢀsurface,ꢀandꢀalsoꢀbyꢀstrongꢀ
synergisticꢀ interactionsꢀ betweenꢀ theꢀ PNPsꢀ andꢀ theꢀ supportꢀ
[22–31].ꢀUsually,ꢀPNPꢀcatalystsꢀareꢀpreparedꢀfromꢀaꢀPdꢀsalt,ꢀonꢀ
aꢀ substrateꢀ orꢀ stabilizer,ꢀ inꢀ theꢀ presenceꢀ ofꢀ aꢀ reducingꢀ agentꢀ
(
Me
beenꢀ developedꢀ [5–7].ꢀ Unfortunately,ꢀ theꢀ useꢀ ofꢀ Me
inconvenientꢀasꢀitꢀisꢀexpensive,ꢀsensitiveꢀtoꢀmoisture,ꢀandꢀeasilyꢀ
3
SiCN)ꢀasꢀtheꢀcyanatingꢀagent,ꢀwhichꢀisꢀlessꢀpoisonous,ꢀhaveꢀ
3
SiCNꢀ isꢀ
*ꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+98‐771‐4541494;ꢀFax:ꢀ+98‐771‐4545188;ꢀE‐mail:ꢀniknam@pgu.ac.ir,ꢀkhniknam@gmail.comꢀ ꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀPersianꢀGulfꢀUniversity.ꢀ
DOI:ꢀ10.1016/S1872‐2067(12)60532‐4ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ34,ꢀNo.ꢀ4,ꢀAprilꢀ2013

ꢀ
KhodabakhshꢀNIKNAMꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ718–722ꢀ ꢀ
ꢀ
O
OH
OH
(MeO) Si
Cl
3
SiO2
O Si
O
Cl
SiO2
Toluene, reflux, 18 h
H
N
OH
3
-CPS
N
H
O
O Si
O
Pd(OAc) / EtOH
SiO2
N
2
NH
O Si
O
N
Pd0
SiO2
O
NH
n
PNP-SBNPP
SBNPP
Schemeꢀ1.ꢀSyntheticꢀrouteꢀforꢀpreparationꢀofꢀPNP‐SBNPP.ꢀ
[32,33].ꢀ Steric,ꢀ electrostatic,ꢀ andꢀ electrostericꢀ factorsꢀ areꢀ re‐
2.2.2.ꢀ ꢀ PreparationꢀofꢀPNP‐SBNPPꢀ
sponsibleꢀforꢀstabilizationꢀofꢀtheꢀPNPsꢀduringꢀtheirꢀsynthesis.ꢀ
Inꢀ thisꢀ paper,ꢀ weꢀ describeꢀ theꢀ preparationꢀ ofꢀ immobilizedꢀ
PNPsꢀ onꢀ piperazine‐modifiedꢀ silicaꢀ (PNP‐SBNPP)ꢀ usingꢀ aꢀ
three‐stepꢀ process.ꢀ First,ꢀ activatedꢀ silicaꢀ wasꢀ reactedꢀ withꢀ
Toꢀ aꢀ mixtureꢀ ofꢀ SBNPPꢀ (1ꢀ g)ꢀ inꢀ absoluteꢀ ethanolꢀ (10ꢀ ml),ꢀ
palladiumꢀacetateꢀ(0.15ꢀg,ꢀ0.67ꢀmmol)ꢀwasꢀadded,ꢀandꢀtheꢀmix‐
tureꢀ wasꢀ stirredꢀ forꢀ 24ꢀ hꢀ atꢀ roomꢀ temperature.ꢀ Theꢀ mixtureꢀ
wasꢀthenꢀfilteredꢀandꢀwashedꢀwithꢀethanolꢀ(10ꢀmlꢀ×ꢀ3).ꢀAfterꢀ
dryingꢀinꢀaꢀvacuumꢀovenꢀatꢀ80ꢀ°C,ꢀPNP‐SBNPPꢀwasꢀobtainedꢀasꢀ
aꢀdarkꢀsolidꢀ(1.1ꢀg).ꢀ ꢀ
3‐chloropropyltrimethoxysilaneꢀinꢀrefluxingꢀtolueneꢀtoꢀproduceꢀ
‐chloropropylsilicaꢀ(3‐CPS)ꢀ[34,35].ꢀSecond,ꢀ3‐CPSꢀwasꢀtreatedꢀ
3
withꢀpiperazineꢀtoꢀgenerateꢀtheꢀcorrespondingꢀsubstrateꢀ[35].ꢀ
Finally,ꢀpalladiumꢀacetateꢀwasꢀreducedꢀonꢀtheꢀSBNPPꢀsubstrateꢀ
usingꢀ absoluteꢀ ethanolꢀ asꢀ theꢀ reducingꢀ agentꢀ (Schemeꢀ 1)ꢀ
2.3.ꢀ ꢀ Generalꢀprocedureꢀforꢀcyanationꢀreactionsꢀ
[36,37].ꢀTheꢀpiperazinesꢀgraftedꢀonꢀtheꢀsilicaꢀsurfaceꢀcanꢀactꢀasꢀ
AꢀmixtureꢀofꢀK
4
[Fe(CN) ]ꢀ(0.3ꢀmmol),ꢀarylꢀhalideꢀ(1ꢀmmol),ꢀ
6
nitrogenꢀ ligandsꢀ toꢀ stabilizeꢀ PNPs,ꢀ asꢀ previouslyꢀ reportedꢀ forꢀ
otherꢀnitrogenꢀligandsꢀ[38–40].ꢀ
Na
2
CO ꢀ (2.5ꢀ mmol),ꢀ PNP‐SBNPPꢀ (0.05ꢀ g,ꢀ 2.81ꢀ mol%),ꢀ andꢀ di‐
3
methylformamideꢀ (DMF;ꢀ 2ꢀ ml)ꢀ wasꢀ stirredꢀ atꢀ 120ꢀ °Cꢀ forꢀ theꢀ
specifiedꢀ time.ꢀ Theꢀ reactionꢀ wasꢀ followedꢀ usingꢀ TLC.ꢀ Afterꢀ
completionꢀ ofꢀ theꢀ reaction,ꢀ theꢀ mixtureꢀ wasꢀ cooledꢀ toꢀ roomꢀ
temperatureꢀ andꢀ filtered,ꢀ andꢀ theꢀ residueꢀ wasꢀ washedꢀ withꢀ
dichloromethaneꢀ (10ꢀ mlꢀ ×ꢀ 3)ꢀ toꢀ separateꢀ theꢀ catalyst.ꢀ Waterꢀ
2.ꢀ ꢀ Experimentalꢀ
2.1.ꢀ ꢀ Generalꢀ
(
50ꢀ ml)ꢀ wasꢀ addedꢀ toꢀ theꢀ organicꢀ phaseꢀ andꢀ theꢀ dichloro‐
methaneꢀwasꢀextractedꢀfromꢀtheꢀwater.ꢀTheꢀorganicꢀphaseꢀwasꢀ
driedꢀoverꢀNa SO .ꢀEvaporationꢀofꢀtheꢀorganicꢀsolventꢀgaveꢀtheꢀ
ChemicalsꢀwereꢀpurchasedꢀfromꢀFluka,ꢀMerck,ꢀandꢀAldrichꢀ
Chemicalꢀcompanies.ꢀInfraredꢀspectraꢀwereꢀrunꢀonꢀaꢀShimadzuꢀ
IR‐435ꢀ spectrometer.ꢀ Hꢀ andꢀ 13Cꢀ NMRꢀ spectraꢀ wereꢀ runꢀ onꢀ
BrukerꢀAvanceꢀ(500ꢀMHz)ꢀandꢀBrukerꢀUltrashieldꢀ(400ꢀMHz)ꢀ
spectrometers.ꢀ Tetramethylsilaneꢀ wasꢀ usedꢀ asꢀ theꢀ standardꢀ
andꢀchemicalꢀshiftsꢀwereꢀreportedꢀinꢀpartsꢀperꢀmillionꢀ(ppm).ꢀ
MeltingꢀpointsꢀwereꢀrecordedꢀonꢀanꢀSMP1ꢀmeltingꢀpointꢀappa‐
ratusꢀinꢀopenꢀcapillaryꢀtubesꢀandꢀareꢀuncorrected.ꢀTheꢀreactionꢀ
progressꢀ wasꢀ followedꢀ byꢀ thin‐layerꢀ chromatographyꢀ (TLC)ꢀ
usingꢀsilicaꢀgelꢀSILG/UVꢀ254ꢀplates.ꢀ3‐CPSꢀwasꢀpreparedꢀusingꢀaꢀ
previouslyꢀreportedꢀprocedureꢀ[34].ꢀ ꢀ
2
4
1
products.ꢀForꢀfurtherꢀpurification,ꢀifꢀneeded,ꢀtheꢀproductsꢀwereꢀ
passedꢀthroughꢀaꢀshortꢀcolumnꢀofꢀsilicaꢀgelꢀusingꢀn‐hexaneꢀasꢀ
theꢀ eluent.ꢀ Allꢀ theꢀ productsꢀ areꢀ knownꢀ compoundsꢀ andꢀ wereꢀ
comparedꢀwithꢀauthenticꢀsamples.ꢀ ꢀ
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
Transmissionꢀ electronꢀ microscopyꢀ (TEM)ꢀ imagesꢀ ofꢀ theꢀ
PNP‐SBNPPꢀcatalystꢀ(Fig.ꢀ1)ꢀshowꢀthatꢀPNPsꢀwithꢀaꢀnearꢀspher‐
2.2.ꢀ ꢀ Catalystꢀpreparationꢀ
2.2.1.ꢀ ꢀ PreparationꢀofꢀSBNPPꢀ
Toꢀaꢀmagneticallyꢀstirredꢀmixtureꢀofꢀ3‐CPSꢀ(3ꢀg)ꢀinꢀtolueneꢀ
(110ꢀ ml),ꢀ piperazineꢀ (1.3ꢀ mmol)ꢀ wasꢀ addedꢀ andꢀ theꢀ mixtureꢀ
wasꢀheatedꢀatꢀ60–70ꢀ°Cꢀinꢀtheꢀpresenceꢀofꢀtriethylamineꢀasꢀaꢀ
protonꢀabstractor,ꢀunderꢀcontinuousꢀstirringꢀinꢀaꢀdryꢀnitrogenꢀ
atmosphereꢀforꢀ48ꢀh.ꢀTheꢀmixtureꢀwasꢀfilteredꢀandꢀwashedꢀwithꢀ
dichloromethaneꢀ (10ꢀ mlꢀ ×ꢀ 3)ꢀ andꢀ ethanolꢀ (10ꢀ mlꢀ ×ꢀ 3).ꢀ Afterꢀ
dryingꢀ inꢀ anꢀ ovenꢀ atꢀ 80ꢀ °C,ꢀ SBNPPꢀ wasꢀ obtainedꢀ asꢀ aꢀ whiteꢀ
powderꢀ(3.4ꢀg)ꢀ[34,35].ꢀ ꢀ
Fig.ꢀ1.ꢀTEMꢀimagesꢀofꢀPNPsꢀonꢀSBNPPꢀsupport.ꢀ

ꢀ
KhodabakhshꢀNIKNAMꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ718–722ꢀ
35
30
25
20
15
10
5
0
3d5/2 = 335.0
3d3/2 = 340.1
5
10
15
20
25
30
35
40
345
340
335
330
Particle size (nm)
Binding energy (eV)
Fig.ꢀ 2.ꢀ Histogramꢀ showingꢀ sizeꢀ distributionꢀ ofꢀ PNPsꢀ onꢀ SBNPPꢀ sub‐
strate.ꢀ
Fig.ꢀ5.ꢀXPSꢀprofileꢀofꢀPNP‐SBNPP.ꢀ
SiO
,ꢀ andꢀ theꢀ otherꢀ peaksꢀ areꢀ indexedꢀ asꢀ theꢀ (111),ꢀ (200),ꢀ
2
icalꢀ morphologyꢀ areꢀ assembledꢀ onꢀ theꢀ SBNPPꢀ supportꢀ withꢀ
relativelyꢀgoodꢀmonodispersity.ꢀAꢀhistogramꢀshowingꢀtheꢀsizeꢀ
distributionꢀ ofꢀ theꢀ PNPsꢀ onꢀ theꢀ SBNPPꢀ substrateꢀ isꢀ shownꢀ inꢀ
Fig.ꢀ2,ꢀbasedꢀonꢀtheꢀdataꢀobtainedꢀfromꢀtheꢀTEMꢀimages.ꢀTheꢀ
averageꢀsizeꢀofꢀPNPsꢀinꢀtheꢀPd‐SBNPPꢀcatalystꢀwasꢀ20ꢀnmꢀ(Fig.ꢀ
(220),ꢀandꢀ(311)ꢀplanesꢀofꢀtheꢀPNPsꢀ[28,30].ꢀ
Figureꢀ5ꢀshowsꢀtheꢀX‐rayꢀphotoelectronꢀspectrumꢀ(XPS)ꢀofꢀ
theꢀ Pd(3d)ꢀ envelope,ꢀ confirmingꢀ theꢀ presenceꢀ ofꢀ metallicꢀ Pdꢀ
particles.ꢀXPSꢀPd(3d5/2)ꢀandꢀPd(3d3/2)ꢀpeaksꢀwereꢀobservedꢀatꢀ
bindingꢀ energiesꢀ ofꢀ 335ꢀ andꢀ 340.1ꢀ eV,ꢀ respectively.ꢀ Theseꢀ
bindingꢀenergiesꢀareꢀsimilarꢀtoꢀthoseꢀreportedꢀinꢀtheꢀliteratureꢀ
forꢀPdꢀmetalꢀ[30,41].ꢀ
2).ꢀ
Theꢀmicroscopicꢀfeaturesꢀofꢀtheꢀcatalystꢀwereꢀobservedꢀus‐
ingꢀscanningꢀelectronꢀmicroscopyꢀ(SEM;ꢀFig.ꢀ3).ꢀInꢀthisꢀfigure,ꢀ
weꢀcanꢀseeꢀtheꢀmorphologyꢀofꢀtheꢀsilicaꢀsubstrate.ꢀItꢀcanꢀbeꢀseenꢀ
thatꢀPNPsꢀwithꢀaꢀnearꢀsphericalꢀmorphologyꢀareꢀwellꢀimmobi‐
lizedꢀonꢀtheꢀSBNPPꢀsubstrate.ꢀ
Theꢀ X‐rayꢀ diffractionꢀ (XRD)ꢀ patternꢀ inꢀ Fig.ꢀ 4ꢀ showsꢀ theꢀ
crystallineꢀstructureꢀofꢀtheꢀPNP‐SBNPPꢀcatalyst.ꢀTheꢀXRDꢀpat‐
ternꢀofꢀtheꢀPNP‐SBNPPꢀcatalystꢀalsoꢀshowsꢀPNPsꢀonꢀtheꢀsilicaꢀ
surface.ꢀTheꢀstrongestꢀpeaksꢀofꢀtheꢀXRDꢀpatternꢀcorrespondꢀtoꢀ
Toꢀ confirmꢀ theꢀ Pdꢀ content,ꢀ theꢀ supportedꢀ catalystꢀ wasꢀ
treatedꢀwithꢀconcentratedꢀHClꢀandꢀHNO ꢀtoꢀdigestꢀtheꢀPdꢀspe‐
3
ciesꢀandꢀthenꢀanalyzedꢀusingꢀinductivelyꢀcoupledꢀplasmaꢀatom‐
icꢀ emissionꢀ spectroscopy.ꢀ Theꢀ Pdꢀ contentꢀ ofꢀ PNP‐SBNPPꢀ wasꢀ
determinedꢀtoꢀbeꢀδꢀ=ꢀ60.0ꢀ(60.0ꢀmg/Lꢀ=ꢀ6.0%,ꢀw/w).ꢀ
TheꢀreactionꢀofꢀiodobenzeneꢀwithꢀK
4
[Fe(CN) ]ꢀwasꢀstudiedꢀ
6
asꢀaꢀmodelꢀreactionꢀandꢀtheꢀcatalyticꢀloadingꢀofꢀPNP‐SBNPPꢀandꢀ
theꢀ reactionꢀ conditionsꢀ wereꢀ screened.ꢀ Theꢀ optimizedꢀ condi‐
tionsꢀ wereꢀ arylꢀ halideꢀ (1ꢀ mmol),ꢀ K
Na CO ꢀ(2.5ꢀmmol),ꢀandꢀPNP‐SBNPPꢀ(0.05ꢀg,ꢀ2.81ꢀmol%)ꢀinꢀ2ꢀ
mlꢀofꢀDMFꢀsolventꢀatꢀ120ꢀ°Cꢀ(Schemeꢀ2).ꢀ
Theꢀ systemꢀ wasꢀ extendedꢀ toꢀ theꢀ reactionꢀ ofꢀ K
withꢀotherꢀarylꢀhalidesꢀ(Tableꢀ1).ꢀTheꢀcyanationꢀofꢀiodobenzeneꢀ
withꢀ K [Fe(CN) ]ꢀ providedꢀ theꢀ nitrileꢀ inꢀ 85%ꢀ yieldꢀ (Tableꢀ 1,ꢀ
entryꢀ2).ꢀBromo‐ꢀandꢀchloro‐benzeneꢀtreatedꢀwithꢀK [Fe(CN) ]ꢀ
4
[Fe(CN) ]ꢀ (0.3ꢀ mmol),ꢀ
6
2
3
(
a)
(b)
4
[Fe(CN) ]ꢀ
6
4
6
4
6
respectivelyꢀprovidedꢀbenzonitrileꢀinꢀ70%ꢀandꢀ51%ꢀyieldsꢀ(Ta‐
bleꢀ1,ꢀentriesꢀ4ꢀandꢀ5).ꢀ3‐Bromopyridineꢀandꢀ3‐chloropyridineꢀ
wereꢀalsoꢀsuccessfullyꢀcyanated,ꢀprovidingꢀaꢀusefulꢀwayꢀofꢀin‐
troducingꢀaꢀcyanideꢀgroupꢀonꢀaꢀpyridineꢀringꢀ(Tableꢀ1,ꢀentriesꢀ7ꢀ
andꢀ 8).ꢀ Cyanationꢀ ofꢀ arylꢀ halidesꢀ inꢀ theꢀ presenceꢀ ofꢀ differentꢀ
functionalitiesꢀsuchꢀasꢀhydroxyl,ꢀamine,ꢀandꢀcarbonylꢀwasꢀalsoꢀ
achievedꢀusingꢀtheꢀpresentꢀcatalyticꢀsystemꢀ(Tableꢀ1,ꢀentriesꢀ6,ꢀ
Fig.ꢀ3.ꢀSEMꢀimagesꢀofꢀPNP‐SBNPP.ꢀ
SiO
2
10–12).ꢀ
Theꢀpossibilityꢀofꢀrecyclingꢀtheꢀcatalystꢀwasꢀexaminedꢀusingꢀ
theꢀreactionꢀofꢀiodobenzeneꢀwithꢀK
4 6
[Fe(CN) ]ꢀunderꢀtheꢀopti‐
SiO
2
(111)
X
K Fe(CN) (0.3 mmol)
4
6
PNP-SBNPP (0.05 g)
Na CO (2.5 mmol)
DMF (2 ml), 120 oC
(200)
R
(220)
(311)
CN
2
3
R
1
mmol
10
20 30 40 50 60 70 80 90 100
o
X = I, Br, Cl
Schemeꢀ2.ꢀPNP‐SBNPP‐catalyzedꢀcyanationꢀreaction.ꢀ
2
/( )
Fig.ꢀ4.ꢀXRDꢀpatternꢀofꢀPNP‐SBNPP.ꢀ

ꢀ
KhodabakhshꢀNIKNAMꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ718–722ꢀ ꢀ
ꢀ
Tableꢀ1ꢀ
PNP‐SBNPP‐catalyzedꢀcyanationꢀreactions.ꢀ
Entryꢀ
1ꢀ
Arylꢀhalideꢀ
Productꢀ
CN
Catalystꢀamountꢀ(g)ꢀ Timeꢀ(h) Yield
ꢀ
*ꢀ(%)ꢀ
TONꢀ
47.93ꢀ
TOFꢀ
7.98ꢀ
0.03ꢀ
0.05ꢀ
0.075ꢀ
0.05ꢀ
0.05ꢀ
0.05ꢀ
0.05ꢀ
ꢀ 6ꢀ
ꢀ 5ꢀ
ꢀ 4ꢀ
ꢀ 8ꢀ
16ꢀ
10ꢀ
ꢀ 7ꢀ
81ꢀ
85ꢀ
90ꢀ
70ꢀ
51ꢀ
72ꢀ
79ꢀ
I
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2ꢀ
30.24ꢀ
21.32ꢀ
24.91ꢀ
18.15ꢀ
25.62ꢀ
28.11ꢀ
6.04ꢀ
5.33ꢀ
3.11ꢀ
1.13ꢀ
2.56ꢀ
4.01ꢀ
I
I
CN
CN
CN
CN
ꢀ
3ꢀ
ꢀ
4ꢀ
Br
Cl
ꢀ
5ꢀ
ꢀ
ꢀ
6ꢀ
HO
Br
HO
CN
ꢀ
7ꢀ
Br
Cl
CN
CN
N
N
ꢀ
N
N
8ꢀ
0.05ꢀ
16ꢀ
57ꢀ
20.28ꢀ
1.27ꢀ
ꢀ
9ꢀ
0.05ꢀ
0.05ꢀ
ꢀ 8ꢀ
16ꢀ
12ꢀ
78ꢀ
63ꢀ
65ꢀ
27.76ꢀ
22.42ꢀ
15.40ꢀ
3.47ꢀ
1.40ꢀ
1.28ꢀ
OHC
Br
OHC
CN
CN
ꢀ
1
0ꢀ
1ꢀ
OHC
Cl
OHC
ꢀ
Br
Br
CN
CN
1
0.075ꢀ
ꢀ
H N
H N
2
12ꢀ
2
I
CN
0.075ꢀ
ꢀ 5ꢀ
79ꢀ
18.72ꢀ
3.74ꢀ
ꢀ
Reactionꢀconditions:ꢀarylꢀhalideꢀ(1ꢀmmol),ꢀK
4
Fe(CN)
6
ꢀ(0.3ꢀmmol),ꢀNa
2
CO ꢀ(2.5ꢀmmol),ꢀDMFꢀ(2ꢀml)ꢀatꢀ120ꢀ°C.ꢀ*Isolatedꢀyield.
3
mizedꢀconditions.ꢀUponꢀcompletion,ꢀtheꢀreactionꢀmixtureꢀwasꢀ
filteredꢀ andꢀ theꢀ catalystꢀ wasꢀ washedꢀ withꢀ dichloromethane.ꢀ
Theꢀrecycledꢀcatalystꢀcouldꢀbeꢀreusedꢀfourꢀtimesꢀwithoutꢀanyꢀ
treatmentꢀ(Fig.ꢀ6).ꢀ
lystꢀefficientlyꢀcatalyzedꢀtheꢀcyanationꢀreactionsꢀofꢀarylꢀhalides,ꢀ
withꢀgoodꢀtoꢀhighꢀyields.ꢀThisꢀcatalystꢀcouldꢀalsoꢀbeꢀrecoveredꢀ
andꢀreusedꢀseveralꢀtimesꢀwithoutꢀnoticeableꢀlossꢀofꢀactivity.ꢀ
Acknowledgmentsꢀ
4.ꢀ ꢀ Conclusionsꢀ
WeꢀthankꢀtheꢀPersianꢀGulfꢀUniversityꢀResearchꢀCouncilꢀforꢀ
partialꢀsupportꢀofꢀthisꢀwork.ꢀWeꢀalsoꢀthankꢀtheꢀSchoolꢀofꢀChem‐
istry,ꢀManchesterꢀUniversity,ꢀforꢀrunningꢀNMR,ꢀTEM,ꢀandꢀSEM.ꢀ
Inꢀconclusion,ꢀthisꢀworkꢀshowsꢀthatꢀPNPsꢀcanꢀbeꢀstabilizedꢀ
efficientlyꢀ byꢀ aꢀ SBNPPꢀsubstrate.ꢀTheseꢀmaterialsꢀcanꢀ beꢀ pre‐
pared,ꢀusingꢀaꢀsimpleꢀprocedure,ꢀfromꢀcommerciallyꢀavailableꢀ
andꢀ relativelyꢀ cheapꢀ startingꢀ materials.ꢀ Theꢀ PNP‐SBNPPꢀ cata‐
Referencesꢀ
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
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GraphicalꢀAbstractꢀ
ꢀ
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Silica‐functionalizedꢀN‐propylpiperazineꢀforꢀimmobilizationꢀofꢀ
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O
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KhodabakhshꢀNIKNAM*,ꢀAbdollahꢀDERIS,ꢀFarhadꢀPANAHIꢀ
Pd0
n
PersianꢀGulfꢀUniversity,ꢀIranꢀ
(0.05 g)
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X
CN
Aꢀ simpleꢀ andꢀ efficientꢀ procedureꢀ forꢀ theꢀ cyanationꢀ ofꢀ arylꢀ halidesꢀ
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4
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2 3
Na CO (2.5 mmol)
DMF (2 ml), 120 oC
(
1 mmol)
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