Ruthenium(II) complex catalysts bearing a 2,6-bis(tetrazolyl)pyridine ligand for the transfer hydrogenation of ketones

Article abstract of DOI:10.1016/S1872-2067(17)62994-2

Three ruthenium(II) complex catalysts bearing 2,6-bis(tetrazolyl)pyridine were synthesized, structurally characterized, and applied in the transfer hydrogenation of ketones. Their different catalytic activities were attributed to the different phosphine ligands on the 4-chloro-2,6-bis(1-(p-tolyl)- 1H- tetrazol-5-yl)pyridine ruthenium(II) complexes, with that based on 1,4- bis(diphenylphosphino) butane exhibiting better catalytic activity. A variety of ketones were reduced to their corresponding alcohols with >95% conversion.

Full text of DOI:10.1016/S1872-2067(17)62994-2

ChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ327–333
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
ꢀ
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
Ruthenium(II)ꢀcomplexꢀcatalystsꢀbearingꢀaꢀ
,6‐bis(tetrazolyl)pyridineꢀligandꢀforꢀtheꢀtransferꢀhydrogenationꢀofꢀ
ketonesꢀ
2
a,
a,b
LiandiꢀWangꢀ *,ꢀTingtingꢀLiuꢀ
ꢀ
aꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences,ꢀDalianꢀ116023,ꢀLiaoning,ꢀChinaꢀ
bꢀUniversityꢀofꢀChineseꢀAcademyꢀofꢀSciences,ꢀBeijingꢀ100049,ꢀChinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Threeꢀruthenium(II)ꢀcomplexꢀcatalystsꢀbearingꢀ2,6‐bis(tetrazolyl)pyridineꢀwereꢀsynthesized,ꢀstruc‐
turallyꢀcharacterized,ꢀandꢀappliedꢀinꢀtheꢀtransferꢀhydrogenationꢀofꢀketones.ꢀTheirꢀdifferentꢀcatalyticꢀ
Receivedꢀ1ꢀNovemberꢀ2017ꢀ
Acceptedꢀ1ꢀDecemberꢀ2017ꢀ
Publishedꢀ5ꢀFebruaryꢀ2018ꢀ
activitiesꢀwereꢀattributedꢀtoꢀtheꢀdifferentꢀphosphineꢀligandsꢀonꢀtheꢀ4‐chloro‐2,6‐bis(1‐(p‐tolyl)‐
ꢀ
1H‐
tetrazol‐5‐yl)pyridineꢀ ruthenium(II)ꢀ complexes,ꢀ withꢀ thatꢀ basedꢀ onꢀ 1,4‐bis(diphenylphosphino)
ꢀ
butaneꢀexhibitingꢀbetterꢀcatalyticꢀactivity.ꢀAꢀvarietyꢀofꢀketonesꢀwereꢀreducedꢀtoꢀtheirꢀcorrespondingꢀ
alcoholsꢀwithꢀ>95%ꢀconversion.ꢀ
Keywords:ꢀ
©ꢀ2018,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
2,6‐Bis(tetrazolyl)pyridineꢀ
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
Rutheniumꢀ
Transferꢀhydrogenationꢀ
Ketoneꢀ
Homogeneousꢀcatalysis
1.ꢀ ꢀ Introductionꢀ
Ho,ꢀ Er,ꢀ Tm,ꢀ andꢀ Yb)ꢀ canꢀ beꢀ efficientlyꢀ sensitizedꢀ usingꢀ
2,6‐bis(tetrazole)pyridineꢀ [26,27].ꢀ Furthermore,ꢀ platinum(II)ꢀ
Nitrogen‐containingꢀligandsꢀhaveꢀbeenꢀwidelyꢀusedꢀinꢀcoor‐
complexesꢀ bearingꢀ 2,6‐bis(tetrazole)pyridineꢀ canꢀ beꢀ usedꢀ asꢀ
luminescentꢀ films,ꢀ dopantsꢀ forꢀ OLEDs,ꢀ andꢀ toꢀ formꢀ supramo‐
lecularꢀ polymericꢀ nanofibersꢀ [28–31].ꢀ Rutheniumꢀ complexesꢀ
dinationꢀchemistryꢀandꢀhomogeneousꢀcatalysisꢀowingꢀtoꢀeaseꢀofꢀ
manipulationꢀandꢀtheꢀhighꢀcatalyticꢀactivityꢀofꢀtheirꢀtransitionꢀ
metalꢀcomplexesꢀ[1–5].ꢀManyꢀpyridyl‐basedꢀsymmetricꢀligands,ꢀ
basedꢀ onꢀ mixedꢀ ligandsꢀ 2,2':6',2''‐terpyridineꢀ andꢀ 2,6‐
ꢀ
suchꢀ asꢀ 2,2':6',2''‐terpyridinesꢀ [6–10],ꢀ 2,6‐bis(oxazolinyl)
ꢀ
ꢀ
pyri‐
bis(tetrazole)pyridineꢀ haveꢀ beenꢀ reportedꢀ andꢀ usedꢀ inꢀ
dye‐sensitizedꢀ solarꢀ cellsꢀ toꢀ affordꢀ novelꢀ rutheniumꢀ dyesꢀ
[32–34].ꢀTheseꢀligandsꢀcanꢀalsoꢀbeꢀcoordinatedꢀwithꢀotherꢀmet‐
als,ꢀ suchꢀ asꢀ aꢀ reportedꢀ seriesꢀ ofꢀ homolepticꢀ complexesꢀ ofꢀ
2,6‐bis(tetrazole)pyridineꢀ withꢀ Co ,ꢀ Ni ,ꢀ Cu ,ꢀ andꢀ Zn ꢀ [35].ꢀ
Furthermore,ꢀ 2,6‐bis(tetrazolyl)pyridineꢀ ligandsꢀ canꢀ recoverꢀ
ꢀ
dinesꢀ [11–15],ꢀ 2,6‐bis(imino)pyridinesꢀ [16–20], andꢀ 2,6‐
ꢀ
ꢀ
bis(pyrazoyl)
pliedꢀinꢀorganicꢀsynthesisꢀandꢀhomogeneousꢀcatalysis.ꢀ
,6‐Bis(tetrazolyl)pyridinesꢀareꢀpyridyl‐basedꢀmultidentateꢀ
ꢀ
ꢀ
pyridines [21–25]ꢀ haveꢀ beenꢀ reportedꢀ andꢀ ap‐
II
II
II
II
2
chelatingꢀagentsꢀcontainingꢀnineꢀNꢀatoms,ꢀandꢀtheirꢀmetalꢀcom‐
plexesꢀ haveꢀ beenꢀ appliedꢀ inꢀ functionalꢀ materialsꢀ fabrication,ꢀ
coordinationꢀ chemistry,ꢀ andꢀ catalysis.ꢀ Theseꢀ ligandsꢀ canꢀ beꢀ
trivalentꢀminorꢀactinidesꢀeffectivelyꢀandꢀselectivelyꢀfromꢀHNO
3
ꢀ
media,ꢀwhileꢀexhibitingꢀweakꢀorꢀalmostꢀnoꢀextractionꢀofꢀtriva‐
usedꢀinꢀtheꢀsynthesisꢀofꢀluminescentꢀmaterialsꢀusingꢀaꢀself‐
semblyꢀ strategy.ꢀ Bothꢀ visibleꢀ andꢀ near‐infraredꢀ (IR)ꢀ lumines‐
cenceꢀemissionsꢀofꢀlanthanideꢀcationsꢀ(Pr,ꢀNd,ꢀSm,ꢀEu,ꢀTb,ꢀDy,ꢀ
ꢀ
as‐
lentꢀ lanthanidesꢀ withꢀ similarꢀ chemicalꢀ propertiesꢀ [36,37].ꢀ
However,ꢀ 2,6‐bis(tetrazolyl)pyridineꢀ ligandsꢀ haveꢀ rarelyꢀ beenꢀ
appliedꢀinꢀcatalyticꢀreactions.ꢀInꢀ2016,ꢀzincꢀpolymersꢀbasedꢀonꢀ
*ꢀCorrespondingꢀauthor.ꢀTel:ꢀ+86‐411‐84379551;ꢀE‐mail:ꢀwangliandi@dicp.ac.cnꢀ
DOI:ꢀ10.1016/S1872‐2067(17)62994‐2ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ39,ꢀNo.ꢀ2,ꢀFebruaryꢀ2018ꢀ ꢀ ꢀ

328ꢀ
LiandiꢀWangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ327–333ꢀ
2,6‐bis(tetrazole)pyridineꢀ withꢀ differentꢀ morphologiesꢀ andꢀ
solvedꢀinꢀCH Cl2ꢀ(100ꢀmL).ꢀThisꢀsolutionꢀwasꢀthenꢀaddedꢀdrop‐
2
particleꢀsizesꢀwereꢀobtainedꢀandꢀusedꢀinꢀtheꢀcyclizationꢀofꢀaro‐
maticꢀ dinitrilesꢀ withꢀ β‐aminoalcoholsꢀ asꢀ heterogeneousꢀ cata‐
lystsꢀ[38].ꢀ
wiseꢀtoꢀaꢀstirredꢀsuspensionꢀofꢀNaN3ꢀ(13.6ꢀg,ꢀ209ꢀmmol)ꢀinꢀDMFꢀ
(100ꢀmL).ꢀAfterꢀadditionꢀwasꢀcompleted,ꢀstirringꢀwasꢀcontinuedꢀ
forꢀ16ꢀhꢀatꢀroomꢀtemperature.ꢀTheꢀreactionꢀmixtureꢀwasꢀthenꢀ
treatedꢀ withꢀ water,ꢀ theꢀ organicꢀ layerꢀ wasꢀ separatedꢀ andꢀ
washedꢀwithꢀwaterꢀ(3200ꢀmL),ꢀandꢀallꢀvolatilesꢀwereꢀremovedꢀ
underꢀreducedꢀpressure.ꢀTheꢀresultantꢀresidueꢀwasꢀpurifiedꢀbyꢀ
columnꢀchromatographyꢀonꢀsilicaꢀgelꢀ(eluent:ꢀpetroleumꢀetherꢀ
Theꢀtransferꢀhydrogenationꢀ(TH)ꢀofꢀunsaturatedꢀsubstratesꢀ
catalyzedꢀ byꢀ transitionꢀ metalꢀ complexesꢀ hasꢀ attractedꢀ muchꢀ
attentionꢀowingꢀtoꢀitsꢀcapacityꢀforꢀreliableꢀreductionꢀusingꢀsim‐
pleꢀproceduresꢀwithꢀmildꢀconditionsꢀandꢀisꢀconsideredꢀaꢀpro‐
spectiveꢀalternativeꢀtoꢀdirectꢀhydrogenationꢀ[39–43].ꢀVersatileꢀ
ruthenium(II)ꢀ2‐aminomethylpyridineꢀ(ampy)ꢀcomplexesꢀhaveꢀ
beenꢀreportedꢀbyꢀBarattaꢀetꢀal.ꢀ[44–49]ꢀandꢀdemonstratedꢀveryꢀ
highꢀcatalyticꢀactivityꢀinꢀtheꢀTHꢀandꢀasymmetricꢀTHꢀ(ATH)ꢀofꢀ
ketones.ꢀ Moreover,ꢀ Noyoriꢀ ruthenium(II)ꢀ complexes,ꢀ contain‐
ingꢀ N‐sulfonylatedꢀ 1,2‐diaminesꢀ asꢀ chiralꢀ ligands,ꢀ haveꢀ beenꢀ
usedꢀ asꢀ efficientꢀ catalystsꢀ forꢀ theꢀ ATHꢀ ofꢀ ketonesꢀ andꢀ iminesꢀ
(60–90ꢀ°C)/CH
2
Cl2ꢀ=ꢀ2:1,ꢀv/v)ꢀtoꢀaffordꢀ2ꢀasꢀaꢀwhiteꢀsolidꢀ(8.7ꢀg,ꢀ
1
35%).ꢀm.p.ꢀ247–248ꢀ°C.ꢀ HꢀNMRꢀ(CDCl3,ꢀ400ꢀMHz,ꢀ25ꢀ°C)ꢀδꢀ8.28ꢀ
(s,ꢀ2ꢀH,ꢀpyridylꢀCH),ꢀ7.11ꢀ(d,ꢀ4ꢀH,ꢀJꢀ=ꢀ8.2ꢀHz)ꢀandꢀ6.92ꢀ(d,ꢀ4ꢀH,ꢀJꢀ=ꢀ
8.3ꢀHz)ꢀ(bothꢀp‐tolylꢀCH),ꢀ2.38ꢀ(s,ꢀ6ꢀH,ꢀp‐tolylꢀCH
13
1
3
).ꢀ C{ H}ꢀNMRꢀ
(CDCl3,ꢀ 100ꢀ MHz,ꢀ 25ꢀ °C)ꢀ δꢀ 150.7,ꢀ 147.1,ꢀ 145.8,ꢀ 140.6,ꢀ 131.8,ꢀ
129.8,ꢀ 127.2,ꢀ 124.8,ꢀ 21.4.ꢀ HRMSꢀ Calcd.ꢀ forꢀ C21
H
16ClN :ꢀ
9
429.1217;ꢀFound:ꢀ429.1212.ꢀ
[
50–55].ꢀ Furthermore,ꢀ transition‐metalꢀ complexesꢀ bearingꢀ aꢀ
Rutheniumꢀ complexꢀ 3a.ꢀ Underꢀ aꢀ nitrogenꢀ atmosphere,ꢀ aꢀ
mixtureꢀ ofꢀ 4‐chloro‐2,6‐bis(1‐(p‐tolyl)‐1H‐tetrazol‐5‐yl)pyri‐
dineꢀ2ꢀ(215ꢀmg,ꢀ0.5ꢀmmol),ꢀRuCl (PPh ꢀ(480ꢀmg,ꢀ0.5ꢀmmol),ꢀ
andꢀCH Cl ꢀ(40ꢀmL)ꢀwasꢀstirredꢀatꢀ40ꢀ°Cꢀforꢀ4ꢀh.ꢀAfterꢀcoolingꢀtoꢀ
ambientꢀtemperature,ꢀ allꢀvolatilesꢀ wereꢀ evaporatedꢀunderꢀre‐
ducedꢀ pressure.ꢀ Theꢀ resultantꢀ residueꢀ wasꢀ purifiedꢀ byꢀ flashꢀ
ligandꢀwithꢀNHꢀfunctionalityꢀalsoꢀexhibitꢀhighꢀcatalyticꢀactivityꢀ
inꢀtransferꢀhydrogenationꢀreactionsꢀ[56–59].ꢀAlthoughꢀvariousꢀ
ligandsꢀ andꢀ theirꢀ transition‐metalꢀ complexesꢀ haveꢀ beenꢀ syn‐
thesizedꢀforꢀTH,ꢀtheꢀdevelopmentꢀofꢀefficientꢀcatalyticꢀsystemsꢀ
isꢀ stillꢀ needed.ꢀ Weꢀ haveꢀ beenꢀ interestedꢀ inꢀ developingꢀ
N‐heterocyclicꢀ ligandsꢀ andꢀ theꢀ correspondingꢀ highlyꢀ effectiveꢀ
catalystꢀsystemꢀforꢀapplicationꢀinꢀhomogeneousꢀcatalysis.ꢀVar‐
iousꢀ pyridyl‐basedꢀ N‐containingꢀ ligandsꢀ andꢀ theirꢀ rutheni‐
um(II)ꢀcomplexesꢀhaveꢀbeenꢀreportedꢀandꢀappliedꢀtoꢀtheꢀTHꢀofꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2
)
3 3
2
2
chromatographyꢀ onꢀ silicaꢀ gelꢀ (eluent:ꢀ CH
2
Cl
2
/CH
3
OH =ꢀ 10:1,ꢀ
ꢀ
v/v).ꢀ Recrystallizationꢀ inꢀ hexane–CH Cl ꢀ (3:1,ꢀ v/v)ꢀ atꢀ roomꢀ
2
2
temperatureꢀ gaveꢀ ruthenium(II)ꢀ complexꢀ 3aꢀ asꢀ aꢀ reddishꢀ
1
brownꢀsolidꢀ(479ꢀmg,ꢀ85%).ꢀm.p.ꢀ>155ꢀCꢀdec.ꢀ HꢀNMRꢀ(CDCl3,ꢀ
ꢀ
ketonesꢀ[60–65]. Herein,ꢀweꢀdescribeꢀtheꢀsynthesisꢀandꢀstruc‐
turalꢀcharacterizationꢀofꢀruthenium(II)ꢀcomplexesꢀofꢀ4‐chloro‐
400ꢀMHz,ꢀ25ꢀC)ꢀδꢀ7.56,ꢀ7.40,ꢀ7.33,ꢀ7.27,ꢀ7.13,ꢀandꢀ6.72ꢀ(eachꢀm,ꢀ
13
1
ꢀ
10:9:3:6:6:6ꢀH,ꢀaromaticꢀCH),ꢀ2.56ꢀ(s,ꢀ6ꢀH,ꢀp‐tolylꢀCH ).ꢀ C{ H}ꢀ
3
2
,6‐bis(1‐(p‐tolyl)‐1H‐tetrazol‐5‐yl)pyridineꢀ withꢀ differentꢀ
ꢀ
NMRꢀ (CDCl3,ꢀ100ꢀ MHz,ꢀ 25ꢀ C)ꢀ δꢀ 153.25,ꢀ 153.22,ꢀ 146.8,ꢀ 145.1,ꢀ
144.2,ꢀ 134.8,ꢀ 134.7,ꢀ 134.2,ꢀ 133.7,ꢀ 133.3,ꢀ 133.2,ꢀ 131.6,ꢀ 130.8,ꢀ
129.9,ꢀ 129.8,ꢀ 129.3,ꢀ 128.7,ꢀ 128.6,ꢀ 128.5,ꢀ 127.8,ꢀ 127.7,ꢀ 125.5,ꢀ
phosphorusꢀligandsꢀandꢀtheirꢀcatalyticꢀbehaviorꢀinꢀTHꢀreactionsꢀ
ofꢀketones.ꢀ ꢀ
31
1
125.3,ꢀ21.5.ꢀ P{ H}ꢀNMRꢀ(CDCl3,ꢀ162ꢀMHz,ꢀ25ꢀC)ꢀδꢀ40.4,ꢀ35.0.ꢀ
2.ꢀ ꢀ Experimentalꢀ
Rutheniumꢀ complexꢀ 3b.ꢀ Underꢀ aꢀ nitrogenꢀ atmosphere,ꢀ aꢀ
mixtureꢀ ofꢀ 1,4‐bis(diphenylphosphino)butaneꢀ (512ꢀ mg,ꢀ 1.2ꢀ
mmol),ꢀRuCl (PPh ꢀ(959ꢀmg,ꢀ1.0ꢀmmol),ꢀandꢀCH Cl ꢀ(50ꢀmL)ꢀ
wasꢀ stirredꢀatꢀ roomꢀtemperatureꢀ forꢀ2ꢀ h.ꢀThen,ꢀ4‐chloro‐2,6‐
2.1.ꢀ ꢀ Generalꢀconsiderationsꢀ
2
)
3 3
2
2
ꢀ
ꢀ
ꢀ
Allꢀmanipulationꢀofꢀair‐ꢀandꢀmoisture‐sensitiveꢀcompoundsꢀ
wasꢀcarriedꢀoutꢀunderꢀaꢀnitrogenꢀatmosphereꢀusingꢀstandardꢀ
bis(1‐(p‐tolyl)‐1H‐tetrazol‐5‐yl)pyridineꢀ2ꢀ(429ꢀmg,ꢀ1.0ꢀmmol)ꢀ
wasꢀaddedꢀandꢀtheꢀmixtureꢀwasꢀstirredꢀatꢀ40ꢀ°Cꢀforꢀ4ꢀh.ꢀAfterꢀ
coolingꢀtoꢀambientꢀtemperature,ꢀallꢀvolatilesꢀwereꢀevaporatedꢀ
underꢀreducedꢀpressure.ꢀTheꢀresultantꢀresidueꢀwasꢀpurifiedꢀbyꢀ
Schlenkꢀtechniques.ꢀSolventsꢀwereꢀdriedꢀandꢀdistilledꢀpriorꢀtoꢀ
1
13
1
useꢀaccordingꢀtoꢀliteratureꢀmethods.ꢀ Hꢀandꢀ C{ H}ꢀNMRꢀspec‐
traꢀwereꢀrecordedꢀonꢀaꢀBrukerꢀDRX‐400ꢀspectrometerꢀ(Bruker,ꢀ
Germany)ꢀandꢀallꢀchemicalꢀshiftꢀvaluesꢀareꢀreferencedꢀtoꢀTMSꢀ=ꢀ
flashꢀchromatographyꢀonꢀsilicaꢀgelꢀ(eluent:ꢀAcOEt/CH
3
OH=ꢀ5:1,ꢀ
ꢀ
v/v).ꢀ Recrystallizationꢀ inꢀ hexane–CH Cl ꢀ (3:1,ꢀ v/v)ꢀ atꢀ roomꢀ
2
2
1
13
0
.00ꢀ ppmꢀ orꢀ CDCl
3
ꢀ (( H),ꢀ 7.26ꢀ ppmꢀ andꢀ ( C),ꢀ 77.16ꢀ ppm).ꢀ
temperatureꢀ gaveꢀ ruthenium(II)ꢀ complexꢀ 3bꢀ asꢀ aꢀ reddishꢀ
1
HRMSꢀ analysisꢀ wasꢀperformedꢀbyꢀtheꢀ AnalysisꢀCenter,ꢀDalianꢀ
Universityꢀ ofꢀ Technology.ꢀ Allꢀ meltingꢀ pointsꢀ areꢀ uncorrected.ꢀ
Thin‐layerꢀ chromatographyꢀ (TLC)ꢀ analysisꢀ wasꢀ performedꢀ
usingꢀglass‐backedꢀplatesꢀcoatedꢀwithꢀsilicaꢀgelꢀ(0.2ꢀmm).ꢀFlashꢀ
columnꢀchromatographyꢀwasꢀperformedꢀonꢀsilicaꢀgelꢀ(200–300ꢀ
mesh).ꢀAllꢀchemicalꢀreagentsꢀwereꢀpurchasedꢀfromꢀcommercialꢀ
suppliersꢀandꢀusedꢀasꢀreceivedꢀunlessꢀotherwiseꢀindicated.ꢀ
brownꢀsolidꢀ(754ꢀmg,ꢀ71%).ꢀm.p.ꢀ>180ꢀCꢀdec.ꢀ HꢀNMRꢀ(CDCl3,ꢀ
400ꢀ MHz,ꢀ 25ꢀ C)ꢀ δꢀ 7.95,ꢀ 7.62,ꢀ 7.45,ꢀ 7.36,ꢀ 7.28,ꢀ 7.07ꢀ andꢀ 6.86ꢀ
(eachꢀm,ꢀ4:8:6:2:4:2:4ꢀH,ꢀaromaticꢀCH),ꢀ2.83,ꢀ2.37,ꢀ2.11ꢀandꢀ1.79ꢀ
13
1
(eachꢀm,ꢀ4CH
2
),ꢀ2.57ꢀ(s,ꢀ6ꢀH,ꢀp‐tolylꢀCH ).ꢀ C{ H}ꢀNMRꢀ(CDCl3,ꢀ
3
100ꢀ MHz,ꢀ 25ꢀ C)ꢀ δꢀ 153.2,ꢀ 145.7,ꢀ 144.8,ꢀ 144.4,ꢀ 136.4,ꢀ 136.0,ꢀ
134.0,ꢀ 133.9,ꢀ 132.7,ꢀ 132.2,ꢀ 131.8,ꢀ 131.6,ꢀ 131.5,ꢀ 131.0,ꢀ 130.2,ꢀ
129.3,ꢀ129.2,ꢀ129.1,ꢀ128.1,ꢀ128.0,ꢀ125.6,ꢀ124.3,ꢀ33.0,ꢀ32.7,ꢀ29.3,ꢀ
1
2
9.1,ꢀ26.1,ꢀ21.7,ꢀ20.1.ꢀ31P{ H}ꢀNMRꢀ(CDCl3,ꢀ162ꢀMHz,ꢀ25ꢀC)ꢀδꢀ
2
.2.ꢀ ꢀ Preparationꢀofꢀligandꢀandꢀrutheniumꢀcomplexesꢀ
40.4,ꢀ33.9.ꢀ ꢀ
Rutheniumꢀ complexꢀ 3c.ꢀ Underꢀ aꢀ nitrogenꢀ atmosphere,ꢀ aꢀ
mixtureꢀ ofꢀ 1,5‐bis(diphenylphosphino)pentaneꢀ (106ꢀ mg,ꢀ 0.24ꢀ
mmol),ꢀRuCl (PPh ꢀ(193ꢀmg,ꢀ0.2ꢀmmol),ꢀandꢀCH Cl ꢀ(10ꢀmL)ꢀ
wasꢀ stirredꢀ atꢀ roomꢀ temperatureꢀ forꢀ 2ꢀ h.ꢀ Thenꢀ 4‐chloro‐2,6‐
4
‐Chloro‐2,6‐bis(1‐(p‐tolyl)‐1H‐tetrazol‐5‐yl)pyridineꢀ(2).ꢀAꢀ
2
6
mixtureꢀ ofꢀ N ,N ‐di‐p‐tolylpyridine‐2,6‐dicarboxamideꢀ (1)ꢀ
20.0ꢀg,ꢀ58ꢀmmol),ꢀPCl5ꢀ(24.2ꢀg,ꢀ116ꢀmmol),ꢀandꢀSOCl ꢀ(120ꢀmL)ꢀ
wereꢀheatedꢀatꢀ80ꢀ°Cꢀforꢀ3ꢀh.ꢀExcessꢀSOCl ꢀwasꢀremovedꢀunderꢀ
reducedꢀpressureꢀandꢀtheꢀresultingꢀimidoylꢀchlorideꢀwasꢀdis‐
2
)
3 3
2
2
(
2
ꢀ
2
bis(1‐(p‐tolyl)‐1H‐tetrazol‐5‐yl)pyridineꢀ 2ꢀ (86ꢀ mg,ꢀ 0.2ꢀ mmol)ꢀ
wasꢀaddedꢀandꢀtheꢀmixtureꢀwasꢀstirredꢀatꢀ40ꢀ°Cꢀforꢀ4ꢀh.ꢀAfterꢀ

ꢀ
LiandiꢀWangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ327–333ꢀ
329ꢀ
p-Tol
coolingꢀtoꢀambientꢀtemperature,ꢀallꢀvolatilesꢀwereꢀevaporatedꢀ
underꢀreducedꢀpressure.ꢀTheꢀresultantꢀresidueꢀwasꢀpurifiedꢀbyꢀ
flashꢀ chromatographyꢀ onꢀ silicaꢀ gelꢀ (eluent:ꢀ CH
CH OH =ꢀ 5:5:1,ꢀ v/v).ꢀ Recrystallizationꢀ inꢀ hexane–CH
v/v)ꢀatꢀroomꢀtemperatureꢀgaveꢀruthenium(II)ꢀcomplexꢀ3cꢀasꢀaꢀ
Cl
p-Tol
p-Tol
p-Tol
2
Cl
2
/AcOEt/
ꢀ
HN
NH
(i)
(ii)
N
N
N
3
ꢀ
2
Cl ꢀ (3:1,ꢀ
2
N
N
N
N
O
O
N
N
N
1
1
2
reddishꢀbrownꢀsolidꢀ(154ꢀmg,ꢀ74%).ꢀm.p.ꢀ>193ꢀCꢀdec.ꢀ HꢀNMRꢀ
(
CDCl3,ꢀ400ꢀMHz,ꢀ25ꢀC)ꢀδꢀ7.87,ꢀ7.58,ꢀ7.44,ꢀ7.38,ꢀ7.30,ꢀ7.23,ꢀ6.96,ꢀ
andꢀ6.74ꢀ(eachꢀm,ꢀ4:8:2:4:2:4:2:4ꢀH,ꢀaromaticꢀCH),ꢀ2.52ꢀ(s,ꢀ6ꢀH,ꢀ
p‐tolylꢀ CH ),ꢀ 2.44,ꢀ 2.17,ꢀ 1.92,ꢀ 1.66,ꢀ andꢀ 1.46ꢀ (eachꢀ m,ꢀ 5CH ).ꢀ
Cl
3
2
p-Tol
p-Tol
13
1
N
N
N
C{ H}ꢀ NMRꢀ (CDCl3,ꢀ 100ꢀ MHz,ꢀ 25ꢀ C)ꢀ δꢀ 153.1,ꢀ 145.3,ꢀ 145.0,ꢀ
44.3,ꢀ 136.0,ꢀ 135.6,ꢀ 133.9,ꢀ 133.8,ꢀ 131.7,ꢀ 130.8,ꢀ 130.0,ꢀ 129.0,ꢀ
28.9,ꢀ128.8,ꢀ127.9,ꢀ127.8,ꢀ125.4,ꢀ123.9,ꢀ27.6,ꢀ27.3,ꢀ26.5,ꢀ26.33,ꢀ
6.26,ꢀ26.2,ꢀ21.5,ꢀ19.85,ꢀ19.79,ꢀ19.7.ꢀ31P{ H}ꢀNMRꢀ(CDCl3,ꢀ162ꢀ
N
(iii)
Cl
N
N
Cl
2
1
1
2
N
N
N
Ru
1
Ph P
3
PPh3
3a
MHz,ꢀ25ꢀC)ꢀδꢀ41.8,ꢀ32.2.ꢀ ꢀ
Cl
2.3.ꢀ ꢀ GeneralꢀprocedureꢀforꢀTHꢀofꢀketonesꢀcatalyzedꢀbyꢀ3ꢀ
p-Tol
p-Tol
N
N
N
N
Underꢀaꢀnitrogenꢀatmosphere,ꢀaꢀmixtureꢀofꢀketoneꢀ(2ꢀmmol),ꢀ
catalystꢀ3ꢀ(0.01ꢀmmol),ꢀandꢀ2‐propanolꢀ(18ꢀmL)ꢀwasꢀstirredꢀatꢀ
(iv)
Cl
N
Cl
N
N
2
N
N
Ru
8
2ꢀCꢀforꢀ10ꢀmin.ꢀThen,ꢀiPrOKꢀsolutionꢀinꢀ2‐propanolꢀ(2.0ꢀmL,ꢀ
3
b, n = 4
Ph2P
PPh2
0.1ꢀ mol/L,ꢀ 0.2ꢀ mmol)ꢀ wasꢀ introducedꢀ toꢀ initiateꢀ theꢀ reaction.ꢀ
3c, n = 5
n
Theꢀ reactionꢀ mixtureꢀ wasꢀ stirredꢀ atꢀ reflux.ꢀ Afterꢀ theꢀ statedꢀ
time,ꢀ0.1ꢀmLꢀofꢀtheꢀreactionꢀmixtureꢀwasꢀsampledꢀandꢀimmedi‐
atelyꢀdilutedꢀwithꢀ0.5ꢀmLꢀofꢀ2‐propanolꢀprecooledꢀtoꢀ0ꢀ°C,ꢀandꢀ
filteredꢀthroughꢀaꢀshortꢀpadꢀofꢀceliteꢀtoꢀquenchꢀtheꢀreactionꢀbyꢀ
removingꢀtheꢀcomplexꢀcatalyst.ꢀTheꢀresultantꢀfiltrateꢀwasꢀusedꢀ
forꢀGCꢀanalysis.ꢀAfterꢀtheꢀreactionꢀwasꢀfinished,ꢀtheꢀmixtureꢀwasꢀ
condensedꢀunderꢀreducedꢀpressureꢀandꢀsubjectedꢀtoꢀflashꢀsilicaꢀ
gelꢀcolumnꢀchromatographyꢀtoꢀaffordꢀtheꢀalcoholꢀproduct.ꢀTheꢀ
alcoholꢀproductsꢀwereꢀidentifiedꢀbyꢀcomparisonꢀwithꢀauthenticꢀ
samplesꢀusingꢀNMRꢀandꢀGCꢀanalyses.ꢀ
Schemeꢀ1.ꢀSynthesisꢀofꢀligandꢀ2ꢀandꢀ complexesꢀ3a–c.ꢀ Conditions:ꢀ (i)ꢀ
PCl ,ꢀSOCl ,ꢀ80ꢀ°C,ꢀ3ꢀh;ꢀ(ii)ꢀNaN ,ꢀCH Cl ,ꢀDMF,ꢀrt,ꢀ16ꢀh;ꢀ(iii)ꢀRuCl (PPh ,ꢀ
ꢀ (0.1ꢀ MPa),ꢀ 40ꢀ °C,ꢀ 4ꢀ h;ꢀ (iv)ꢀ RuCl (PPh ,ꢀ dppbꢀ orꢀ dpppe,ꢀ
ꢀ(0.1ꢀMPa),ꢀ40ꢀ°C,ꢀ4ꢀh.ꢀ
5
2
3
2
2
2
)
3 3
CH
CH
2
Cl
Cl
2
,ꢀ N
,ꢀN
2
2
)
3 3
2
2
2
vicinityꢀ(Fig.ꢀ1).ꢀTheꢀP(1)–Ru–P(2)ꢀangleꢀinꢀ3bꢀwasꢀ92.54(3)°,ꢀ
suggestingꢀthatꢀtheꢀtwoꢀPPh ꢀligandsꢀwereꢀalmostꢀorthogonalꢀtoꢀ
eachꢀ other.ꢀ P(1)ꢀ andꢀ Cl(1)ꢀ wereꢀ almostꢀ linearꢀ toꢀ eachꢀ otherꢀ
P(1)–Ru–Cl(1),ꢀ171.32(3)°)ꢀandꢀpositionedꢀonꢀtwoꢀsidesꢀofꢀtheꢀ
ligandꢀ plane.ꢀ Theꢀ presenceꢀ ofꢀ threeꢀ Ru–Nꢀ bondsꢀ (2.058(2),ꢀ
2
(
2
2
.079(2),ꢀ andꢀ 2.096(2)ꢀ Å),ꢀ twoꢀ Ru–Pꢀ bondsꢀ (2.3186(8)ꢀ andꢀ
.3467(9)ꢀ Å),ꢀ anꢀ Ru–Clꢀ bondꢀ (2.4538(8)ꢀ Å),ꢀ aꢀ N(5)–Ru–P(2)ꢀ
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
angleꢀ ofꢀ 171.79(6)°,ꢀ andꢀ aꢀ P(1)–Ru–Cl(1)ꢀ angleꢀ ofꢀ 171.32(3)°ꢀ
2
6
Aꢀ mixtureꢀ ofꢀ N ,N ‐di‐p‐tolylpyridine‐2,6‐dicarboxamideꢀ 1,ꢀ
,ꢀandꢀSOCl ꢀwereꢀheatedꢀtoꢀaffordꢀanꢀimidoylꢀchloride.ꢀTheꢀ
PCl
5
2
ligand,ꢀ 4‐chloro‐2,6‐bis(1‐(p‐tolyl)‐1H‐tetraz‐ol‐5‐yl)pyridineꢀ
,ꢀwasꢀthenꢀobtainedꢀbyꢀcycloadditionꢀofꢀtheꢀimidoylꢀchlorideꢀtoꢀ
NaN ꢀ inꢀ DMF.ꢀ Treatmentꢀ ofꢀ ligandꢀ 2ꢀ withꢀ rutheniumꢀ com‐
poundsꢀinꢀCH Cl ꢀgaveꢀcomplexesꢀ3a–cꢀunderꢀreactionꢀcondi‐
2
3
2
2
tionsꢀ(iii)ꢀorꢀ(iv)ꢀ(Schemeꢀ1).ꢀDueꢀtoꢀcyclicꢀtension,ꢀcomplexesꢀ3ꢀ
withꢀ2,ꢀ3,ꢀorꢀ6‐carbonꢀalkylꢀchainsꢀbetweenꢀtheꢀtwoꢀphosphorusꢀ
ligandsꢀ wereꢀ notꢀ obtainedꢀ underꢀ theꢀ sameꢀ conditions.ꢀ Com‐
plexesꢀ3a–cꢀwereꢀstableꢀwhenꢀexposedꢀtoꢀairꢀatꢀambientꢀtem‐
perature.ꢀ
Theꢀ structuresꢀ ofꢀ complexesꢀ 3ꢀ wereꢀ supportedꢀ byꢀ NMRꢀ
analysisꢀinꢀsolution.ꢀTheꢀchemicalꢀshiftsꢀofꢀtheꢀpyridylꢀCHꢀhy‐
drogenꢀatomsꢀinꢀcomplexesꢀ3ꢀwereꢀshiftedꢀupfieldꢀbyꢀ0.3–0.7ꢀ
ppmꢀinꢀtheꢀprotonꢀNMRꢀspectrumꢀcomparedꢀwithꢀthoseꢀofꢀlig‐
andꢀ precursorꢀ 2.ꢀ Complexesꢀ 3a–cꢀ showedꢀ twoꢀ signalsꢀ inꢀ theꢀ
31
1
P{ H}ꢀ NMRꢀ spectra,ꢀ suggestingꢀ thatꢀ theꢀ twoꢀ phosphorousꢀ
groupsꢀwereꢀpositionedꢀinꢀdifferentꢀenvironments.ꢀSingleꢀcrys‐
talsꢀ ofꢀ 3bꢀ suitableꢀ forꢀ X‐rayꢀ crystallographicꢀ studyꢀ wereꢀ ob‐
tainedꢀ toꢀ furtherꢀ validateꢀ theꢀ complexꢀ structureꢀ [66].ꢀ Inꢀ theꢀ
solidꢀ state,ꢀ theꢀ cationicꢀ metalꢀ centerꢀ ofꢀ complexꢀ 3bꢀ wasꢀ sur‐
roundedꢀbyꢀtridentateꢀNNNꢀligandꢀ2,ꢀtwoꢀPPh
chlorideꢀanion,ꢀwithꢀanotherꢀdissociatedꢀchlorideꢀanionꢀinꢀtheꢀ
2
ꢀligands,ꢀandꢀaꢀ
Fig.ꢀ 1.ꢀ Molecularꢀ structureꢀ ofꢀ 3bꢀ withꢀ aꢀ H Oꢀ moleculeꢀ andꢀ chlorideꢀ
anionꢀomittedꢀforꢀclarity.ꢀ
2

330ꢀ
LiandiꢀWangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ327–333ꢀ
identifiedꢀaꢀsix‐coordinateꢀmetalꢀcenterꢀinꢀcomplexꢀ3bꢀwithꢀaꢀ
distortedꢀbipyramidalꢀenvironment.ꢀ ꢀ
>97%ꢀ conversionsꢀ forꢀ theseꢀ ketonesꢀ inꢀ 20–40ꢀ minꢀ (Tableꢀ 1,ꢀ
entriesꢀ 7,ꢀ 12,ꢀ andꢀ 13).ꢀ Electron‐donatingꢀ substituent‐bearingꢀ
aromaticꢀketonesꢀo‐,ꢀm‐,ꢀandꢀp‐methylacetophenoneꢀrequiredꢀaꢀ
longerꢀtimeꢀtoꢀbeꢀtransformedꢀintoꢀtheꢀtargetꢀreductionꢀprod‐
Ruthenium(II)ꢀ complexesꢀ 3a–cꢀ wereꢀ testedꢀ asꢀ catalystsꢀ inꢀ
theꢀTHꢀofꢀketonesꢀ(Tableꢀ1).ꢀUsingꢀ0.5ꢀmol%ꢀofꢀ3ꢀasꢀcatalyst,ꢀ
withꢀ aꢀmolarꢀratioꢀofꢀ 200/20/1ꢀ forꢀketone/base/catalystꢀ andꢀ
iPrOKꢀasꢀtheꢀbaseꢀpromoter,ꢀtransferꢀhydrogenationꢀofꢀaceto‐
phenoneꢀ wasꢀ conductedꢀ inꢀ 2‐propanolꢀ atꢀ 82ꢀ °C.ꢀ Toꢀ achieveꢀ
uctsꢀ (Tableꢀ 1,ꢀ entriesꢀ 5,ꢀ 10,ꢀ andꢀ 11).ꢀ Propiophenone,ꢀ 2‐
ace‐
ꢀ
tonaphthone,ꢀ2‐benzoylpyridine,ꢀandꢀbenzophenoneꢀwereꢀalsoꢀ
smoothlyꢀreducedꢀtoꢀtheirꢀcorrespondingꢀalcoholsꢀinꢀ93%–96%ꢀ
conversionsꢀwithinꢀ1–2ꢀhꢀ(Tableꢀ1,ꢀentriesꢀ14–17).ꢀDueꢀtoꢀtheꢀ
rigidityꢀ ofꢀ theꢀ carbonylꢀ rings,ꢀ 1‐tetraloneꢀ andꢀ 9‐fluorenoneꢀ
proceededꢀwithꢀtheꢀpoorestꢀreactionꢀactivityꢀaffordingꢀ70%ꢀandꢀ
83%ꢀconversionꢀafterꢀ2ꢀandꢀ0.5ꢀh,ꢀrespectively,ꢀwithꢀextendedꢀ
reactionꢀtimesꢀproducingꢀnoꢀimprovementꢀ(Tableꢀ1,ꢀentriesꢀ18ꢀ
andꢀ19).ꢀForꢀtheꢀreductionꢀofꢀaliphaticꢀketones,ꢀcyclohexanoneꢀ
andꢀlinearꢀ2‐heptanoneꢀachievedꢀ>95%ꢀconversionsꢀinꢀ40ꢀminꢀ
andꢀ3ꢀh,ꢀrespectivelyꢀ(Tableꢀ1,ꢀentriesꢀ9ꢀandꢀ21),ꢀwhileꢀcyclo‐
pentanoneꢀwasꢀreducedꢀtoꢀitsꢀdesiredꢀalcoholꢀinꢀ90%ꢀconver‐
sionꢀinꢀ2ꢀh,ꢀwithꢀnoꢀfurtherꢀtransformationꢀtakingꢀplaceꢀwhenꢀ
theꢀreactionꢀtimeꢀwasꢀextendedꢀ(Tableꢀ1,ꢀentryꢀ20).ꢀTheꢀdiffer‐
enceꢀbetweenꢀtheꢀcatalyticꢀactivityꢀofꢀcomplexesꢀ3a–cꢀinꢀtheꢀTHꢀ
>96%ꢀyield,ꢀcorrespondingꢀcomplexesꢀ3a,ꢀ3bꢀandꢀ3cꢀwereꢀre‐
actedꢀforꢀ1,ꢀ1,ꢀandꢀ2ꢀh,ꢀrespectivelyꢀ(Tableꢀ1,ꢀentriesꢀ1–3).ꢀFur‐
therꢀresearchꢀintoꢀtheꢀcatalystꢀactivitiesꢀwasꢀperformedꢀusingꢀ
3aꢀandꢀ3b.ꢀForꢀo‐methylacetophenone,ꢀbothꢀcatalystsꢀrequiredꢀ
3ꢀhꢀtoꢀreachꢀ97%ꢀconversionꢀ(Tableꢀ1,ꢀentriesꢀ4ꢀandꢀ5).ꢀWhenꢀ
o‐chloroacetophenoneꢀ wasꢀ tested,ꢀ 3bꢀ showedꢀ betterꢀ catalyticꢀ
activity,ꢀ withꢀ onlyꢀ 20ꢀ minꢀ neededꢀ toꢀ reachꢀ 97%ꢀ conversionꢀ
(
Tableꢀ1,ꢀentriesꢀ6ꢀandꢀ7).ꢀFurthermore,ꢀforꢀcyclohexanone,ꢀ3bꢀ
showedꢀbetterꢀcatalyticꢀactivityꢀthanꢀ3aꢀ(Tableꢀ1,ꢀentriesꢀ8ꢀandꢀ
).ꢀNext,ꢀ0.5ꢀmol%ꢀ3bꢀasꢀcatalystꢀwasꢀusedꢀinꢀtypicalꢀreactions,ꢀ
9
exhibitingꢀ veryꢀ goodꢀ catalyticꢀ activityꢀ forꢀ theꢀ transferꢀ hydro‐
genationꢀ ofꢀ o‐,ꢀ m‐,ꢀ andꢀ p‐chloroacetophenoneꢀ andꢀ achievingꢀ
Tableꢀ1ꢀ
Transferꢀhydrogenationꢀofꢀketonesꢀcatalyzedꢀbyꢀcomplexesꢀ3a–c.ꢀ
ꢀ
ꢀ
a
ꢀa
Entryꢀ
Ru(II)ꢀcat.ꢀ
Ketoneꢀ
Timeꢀ(h)ꢀ
1ꢀ
Yield ꢀ(%)ꢀ
Entryꢀ
12ꢀ
Ru(II)ꢀcat.ꢀ
Ketoneꢀ
Timeꢀ(h)ꢀ
2/3ꢀ
Yield ꢀ(%)ꢀ
1ꢀ
3aꢀ
97ꢀ
3bꢀ
98ꢀ
ꢀ
ꢀ
2
ꢀ
3bꢀ
3cꢀ
3aꢀ
3bꢀ
3aꢀ
3bꢀ
3aꢀ
3bꢀ
3bꢀ
3bꢀ
1ꢀ
2ꢀ
97ꢀ
96ꢀ
97ꢀ
97ꢀ
97ꢀ
97ꢀ
98ꢀ
98ꢀ
95ꢀ
93ꢀ
13ꢀ
14ꢀ
15ꢀ
16ꢀ
17ꢀ
18ꢀ
19ꢀ
20ꢀ
3bꢀ
3bꢀ
3bꢀ
3bꢀ
3bꢀ
3bꢀ
3bꢀ
3bꢀ
1/2ꢀ
2ꢀ
97ꢀ
93ꢀ
95ꢀ
96ꢀ
94ꢀ
70ꢀ
83ꢀ
90ꢀ
3ꢀ
ꢀ
4ꢀ
3ꢀ
1ꢀ
ꢀ
O
N
5ꢀ
3ꢀ
Ph
1ꢀ
ꢀ
O
6ꢀ
1ꢀ
2ꢀ
ꢀ
7ꢀ
1/3ꢀ
1ꢀ
2ꢀ
ꢀ
O
8ꢀ
1/2ꢀ
2ꢀ
ꢀ
ꢀ
O
9ꢀ
2/3ꢀ
2ꢀ
ꢀ
ꢀ
O
1
0ꢀ
1ꢀ
21ꢀ
ꢀ
3bꢀ
Me
4
3ꢀ
ꢀ
97ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
1
2ꢀ
Conditions:ꢀKetone,ꢀ2.0ꢀmmolꢀ(0.1ꢀmol/Lꢀinꢀ20ꢀmLꢀofꢀiPrOH);ꢀcatalyst,ꢀ0.5ꢀmol%ꢀ3;ꢀketone/iPrOK/catalystꢀ=ꢀ200:20:1;ꢀ0.1ꢀMPaꢀN
2
,ꢀ82ꢀC.ꢀ ꢀ
a
ꢀDeterminedꢀbyꢀGCꢀanalysis.

ꢀ
LiandiꢀWangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ327–333ꢀ
331ꢀ
Cl
Ru(II)ꢀcatalystꢀforꢀtheꢀtransferꢀhydrogenationꢀofꢀketones.ꢀ
Referencesꢀ
p-Tol
p-Tol
N
N
N
N
N
Cl
N
Cl
N
N
N
Ru
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3b
4
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p-Tol
p-Tol
[
N
N
N
O
OH
N
O
N
N
[6] A.ꢀArrigo,ꢀA.ꢀSantoro,ꢀF.ꢀPuntoriero,ꢀP.ꢀP.ꢀLainé,ꢀS.ꢀCampagna,ꢀCoord.ꢀ
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N
N
Cl
Ru
+
base
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PPh2
I
Cl
4
Cl
2
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p-Tol
p-Tol
p-Tol
R1
N
R2 p-Tol
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N
N
N
N
N
N
N
N
H
N
N
Cl
N
O
N
N
Cl
N
N
N
N
Ru
Ru
4
2011,ꢀ40,ꢀ1459–1511.ꢀ
Ph2P
PPh2 4b
Ph2P
PPh2 III
4
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[
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11,ꢀ48–65.ꢀ
N
R2
H
N
N
[
N
N
N
Cl
N
Ru
O
[
Ph2P
PPh2
4
R1
R2
II
8
Schemeꢀ2.ꢀAꢀproposedꢀmechanism.ꢀ
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ofꢀ ketonesꢀ wasꢀ presumablyꢀ attributedꢀ toꢀ theꢀ phosphorusꢀ lig‐
ands.ꢀTheseꢀresultsꢀsuggestedꢀthatꢀdppbꢀinꢀ3bꢀwasꢀmoreꢀfavor‐
ableꢀforꢀstabilizingꢀtheꢀactiveꢀcatalyticꢀspecies.ꢀ
[
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[
2016,ꢀ6,ꢀ65205–65221.ꢀ
Inꢀtheꢀruthenium‐catalyzedꢀtransferꢀhydrogenationꢀreactionꢀ
ofꢀketones,ꢀtheꢀcatalyticallyꢀactiveꢀspeciesꢀisꢀusuallyꢀaꢀRu(II)Hꢀ
complexꢀ generatedꢀ inꢀ situꢀ fromꢀ aꢀ Ru(II)Clꢀ complexꢀ catalystꢀ
precursorꢀ [49,62,64,67–70].ꢀ Toꢀ confirmꢀ theꢀ reactionꢀ mecha‐
[
22] Y.ꢀS.ꢀL.ꢀV.ꢀNarayana,ꢀM.ꢀBaumgarten,ꢀK.ꢀMüllen,ꢀR.ꢀChandrasekar,ꢀ
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13–31.ꢀ
[
[
[
[
[
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nism,ꢀcomplexꢀ3bꢀwasꢀtreatedꢀwithꢀiPrOKꢀorꢀK
2
CO
3
ꢀinꢀrefluxingꢀ
1
Trans.,ꢀ2014,ꢀ43,ꢀ7577–7588.ꢀ
2‐propanolꢀ underꢀ aꢀ nitrogenꢀ atmosphere.ꢀ Theꢀ Hꢀ NMRꢀ spec‐
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DaltonꢀTrans.,ꢀ2012,ꢀ41,ꢀ1268–1277.ꢀ
trumꢀofꢀtheꢀinseparableꢀproductꢀmixtureꢀshowedꢀaꢀdoubletꢀofꢀ
2
doubletsꢀatꢀ−6.00ꢀppmꢀwithꢀ J(H,P)ꢀ=ꢀ107.9ꢀandꢀ24.4ꢀHz,ꢀwhichꢀ
suggestedꢀ theꢀ presenceꢀ ofꢀ Ru–Hꢀ functionality.ꢀ Theseꢀ resultsꢀ
impliedꢀthatꢀcomplexesꢀ3ꢀcouldꢀreadilyꢀgeneratedꢀRu(II)Hꢀspe‐
ciesꢀ inꢀ situꢀ underꢀ theꢀ statedꢀ conditions.ꢀ Thisꢀ Ru(II)Hꢀ speciesꢀ
thenꢀcatalyzesꢀtheꢀketoneꢀreductionꢀviaꢀaꢀpossibleꢀinner‐sphereꢀ
pathwayꢀ(Schemeꢀ2).ꢀUnfortunately,ꢀexpectedꢀRu(II)Hꢀcomplexꢀ
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4bꢀwasꢀnotꢀsuccessfullyꢀisolated.ꢀ ꢀ
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3132–13137.ꢀ
4.ꢀ ꢀ Conclusionsꢀ
1
[
31] C.ꢀA.ꢀStrassert,ꢀC.ꢀH.ꢀChien,ꢀM.ꢀD.ꢀGalvezꢀLopez,ꢀD.ꢀKourkoulos,ꢀD.ꢀ
Ruthenium(II)ꢀ complexesꢀ basedꢀ onꢀ 2,6‐bis(tetrazolyl)pyri‐
ꢀ
ꢀ
Hertel,ꢀK.ꢀ Meerholz,ꢀ L.ꢀ DeꢀCola,ꢀ Angew.ꢀChem.ꢀInt.ꢀEd.,ꢀ2011,ꢀ50,ꢀ
dineꢀhaveꢀbeenꢀsuccessfullyꢀsynthesized,ꢀcharacterizedꢀbyꢀNMRꢀ
andꢀX‐rayꢀcrystallographicꢀanalysis,ꢀandꢀappliedꢀinꢀtheꢀtransferꢀ
hydrogenationꢀofꢀketones.ꢀTheꢀruthenium(II)ꢀcomplexꢀbasedꢀonꢀ
946–950.ꢀ
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1
,4‐bis(diphenylphosphino)butaneꢀ exhibitedꢀ betterꢀ catalyticꢀ
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activity,ꢀsmoothlyꢀreducingꢀvariousꢀtypesꢀofꢀketonesꢀtoꢀtheꢀcor‐
respondingꢀalcoholsꢀwithꢀgoodꢀcatalyticꢀefficiency.ꢀTheꢀpresentꢀ
workꢀ demonstratesꢀ anꢀ efficientꢀ pyridyl‐basedꢀ symmetricalꢀ
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L.ꢀY.ꢀHan,ꢀI.ꢀBedja,ꢀR.ꢀK.ꢀGupta,ꢀQ.ꢀShen,ꢀJ.ꢀOtsuki,ꢀJ.ꢀPowerꢀSources,ꢀ

332ꢀ
LiandiꢀWangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ327–333ꢀ
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2018,ꢀ39:ꢀ327–333ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(17)62994‐2
Ruthenium(II)ꢀcomplexꢀcatalystsꢀbearingꢀaꢀ2,6‐bis(tetrazolyl)pyridineꢀligandꢀforꢀtheꢀtransferꢀhydrogenationꢀofꢀketonesꢀ
LiandiꢀWangꢀ*,ꢀTingtingꢀLiuꢀ
DalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences;ꢀUniversityꢀofꢀChineseꢀAcademyꢀofꢀSciencesꢀ
O
OH
OH
R2
O
Ru(II) cat.
o
R1
R2
iPrOK, 82 C
R1
Cl
Cl
p-Tol
p-Tol
p-Tol
p-Tol
N
N
N
N
N
N
Ru(II) cat.:
Cl
Cl
Cl
Cl
N
N
N
N
N
N
N
N
N
N
N
N
Ru
Ru
Ph P
3
PPh3
Ph P
2
PPh2
n
n = 4, 5
ꢀ
Threeꢀruthenium(II)ꢀcomplexꢀcatalystsꢀbearingꢀ2,6‐bis(tetrazolyl)pyridineꢀwereꢀsynthesizedꢀandꢀappliedꢀinꢀtheꢀtransferꢀhydrogenationꢀofꢀ
ketones.ꢀ Theirꢀ differentꢀ catalyticꢀ activitiesꢀ wereꢀ attributedꢀ toꢀ theꢀ phosphineꢀ ligandsꢀ inꢀ theꢀ 4‐chloro‐2,6‐bis(1‐(p‐tolyl)‐1H‐te‐
ꢀ
trazol‐5‐yl)pyridineꢀruthenium(II)ꢀcomplexes.ꢀTheꢀruthenium(II)ꢀcomplexꢀbasedꢀonꢀ1,4‐bis(diphenylphosphino)butaneꢀexhibitedꢀbetterꢀ
catalyticꢀactivity,ꢀreducingꢀaꢀvarietyꢀofꢀketonesꢀtoꢀtheirꢀcorrespondingꢀalcoholsꢀwithꢀ>95%ꢀconversion.ꢀ
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吡啶基桥联双四唑钌(II)配合物催化酮的转移氢化反应
a,*
a,b
王连弟 , 刘婷婷
a
中国科学院大连化学物理研究所, 辽宁大连116023
b
中国科学院大学, 北京100049
摘要: 含氮配体具有稳定性好、易于合成等优点, 而且其过渡金属配合物表现出较高的催化活性, 因而在配位化学和均相
催化等研究领域受到了广泛关注. 基于吡啶骨架的三齿NNN配体具有良好的配位能力和丰富的配位模式，如吡啶桥联的
对称配体2,2':6',2''-三吡啶、2,6-双噁唑啉基吡啶、2,6-双亚胺基吡啶和2,6-双吡唑基吡啶等在有机合成及配合物催化剂制备
等方面得到广泛应用. 2,6-双四唑基吡啶也是基于吡啶的多齿配体, 已被用于合成发光材料或高效回收次锕系元素等, 但
是其在催化领域的应用较少.
过渡金属催化的不饱和化合物的转移氢化反应具有反应条件温和、不直接使用氢气等优点, 因而受到越来越多的关
注. 一系列优异的配体及配合物在转移氢化反应中脱颖而出, 如对甲苯磺酰手性二胺配体、2-甲胺基吡啶钌配合物、配体
中含有NH官能团的过渡金属配合物等. 我们也报道了几种吡啶基桥联的含氮配体及其钌配合物, 并应用于催化酮的转移
氢化反应. 在此基础上, 本文合成了三种连有不同膦配体的2,6-双四唑基吡啶钌配合物, 并用于催化酮的转移氢化反应.
2
6
从N ,N -二对甲苯基-2,6-吡啶二甲酰胺(1)出发, 经氯代/环化两步反应合成4-氯吡啶基桥联双四唑化合物(2), 配体2与
RuCl (PPh ) 在对应的反应条件下制得三种连有不同膦配体的2,6-双四唑基吡啶钌配合物(3), 其分子结构通过核磁共振波
2
3 3
谱和X射线单晶晶体结构测定得到确认. 将这三种钌配合物应用于催化酮的转移氢化反应, 当催化剂用量为0.5 mol%时,
在异丙醇回流条件下, 比较连有不同膦配体的2,6-双四唑基吡啶钌配合物的催化活性. 膦配体为1,4-双(二苯基膦)丁烷的钌
配合物3b表现出更高的催化活性, 含有双三苯基膦的钌配合物3a则表现出与3b相当或略低的催化活性, 含有1,5-双(二苯基
膦)戊烷的钌配合物3c活性最差. 以3b为催化剂拓展了一系列酮底物, 取代的芳香酮、链状和环状的脂肪酮都可以高效地被
还原, 大部分酮底物以>95%的转化率还原成相应的醇. 含有氯取代基的苯乙酮对反应有较大的加速作用, 反应时间更短,
转化率更高. 由于羰基环的张力, 1-四氢萘酮与9-芴酮转化率略低.
结合实验结果与相关文献, 提出了一条基于Ru-H活性中间体的内层反应机理: 钌配合物在iPrOK作用下生成Ru(II)-烷
氧基中间体I, 随后发生β-H消除反应脱去一分子丙酮得到Ru-H配合物, Ru-H配合物与酮底物作用经过渡态II生成另一分子
Ru(II)-烷氧基中间体III, 随后异丙醇与烷氧基发生交换生成目标产物, 同时生成中间体I完成催化循环.
关键词: 2,6-双四唑基吡啶; 钌; 转移氢化; 酮; 均相催化
收稿日期: 2017-11-01. 接受日期: 2017-12-01. 出版日期: 2018-02-05.
*
通讯联系人. 电话: (0411)84379551; 电子信箱: wangliandi@dicp.ac.cn
本文的电子版全文由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).