Studies on the sequential reaction intermediates in aliphatic C‑H bond
functionalization initiated by a bis(μ
‑oxo)dinickel(3) complex
著者 Cho Jaeheung
著者別名 趙, 栽興
journal or
publication title
博士学位論文要旨 論文内容の要旨および論文審査 結果の要旨／金沢大学大学院自然科学研究科
volume 平成19年3月
page range 45‑51
year 2007‑03‑01
URL http://hdl.handle.net/2297/14585
氏名 学位の種類 学位記番号 学位授与の日付 学位授与の要件 学位授与の題目
趙栽興 博士（学術）
博甲第757号 平成１７年９月３０日
課程博士（学位規則第４条第１項）
StudiesontheSequentialReactionlntermediatesinAliphaticC-HBond FunctionalizationlnitiatedbyaBis(ノリ-ＯＸＯ)dinickel(IⅡ)Colnplex
(ビス（｣ｕ－オキソ)二核ニッケル(Ⅲ)錯体の酸化反応により誘導される反応中間 体の同定と反応機構に関する研究)
鈴木正樹（自然科学研究科・教授）
藤波修平（自然科学研究科･助教授），池田修（自然科学研究科･教授），
猪股勝彦（自然科学研究科・教授），磯邉清（自然科学研究科・教授）
論文審査委員(主査）
論文審査委員(副査）
AbStract
Reactionof［Ni2(OH)2(Me2-tpa)2]2＋（１）（Me2-tpa＝bis(6-methyl-2-pyridylmetllyl）
(Z-pylidylmethyl)amine)withexcessofH202underO2causedoxidationofalnethylenegroupof Me2-tpaligandtogiveamVnealkylatedligandandoxidationofalnethylgrouptoaffbrd ligandbasedcarboxylateandalkoxideasfinaloxidationproductsAseliesoftllesequential reactioninterlnediatesproducedintheoxidationpaihways，ａbis砂oxo)dinickcl(111)，
[Ni2(O)2(Me2-tpa)2]針（２），ａbis(ﾉﾙsuperoxo)dinickel(11)，［Ni2(02)2(Me2-tpa)2]2＋(3)，ａ Ｕ卜hydruxo)似alkylperoxo)dimckel(11)，［Ni2(OH)(Me2-tpa)(Me-tpa-CH200)]2＋(4)，anda bis似alkylperoxo)dimckel(11）complex，［Ni2(Me-tpa-CH200)2]2＋(5)，wasisolatedand cllaracterizedbyvanousphysicochenlicallneasurementsincludingX-raycrystallographyand tlleiroxidationmec11anisInswereinvestigated・ReactionoflwitllH202inmetllano1at40oC generated3・Disproportionationof3intheabse､ｃｅｏｆＨ２０２ａｔ－４０ｏＣｐｒｏｄｕｃｅｄＺａｎｄ０２．
Therlnaldccompositionof2underN2generatesanjV凸dealkylatedligandMe-dpa ((6-metllyl-2-pyridylmetllyl)(z-pyridylmetllyl)amine)andaligand-couplingdimerMe-tpa-CH2‐
CH2-tpaMe・ThefbrInationofMe-tpa-CH2-CH2-tpa-Mesuggeststllataligand-basedradical Me-tpaPCH2・isgeneratedasareactionintelrnediateproducedpresumablybyH-atonlabstraction bytlleoxogro叩.Isotopelabelingexperimentsrevealedtllatintrarnolecularcouplingoccurs・In contrast，decompositionofZand3inthepresenceofO2gavealigand-basedcarboxylate Me-tpa-COO-andalcoholMe-tpa-CH20HinsteadofMe-tpa-CH2-CH2-tpa-Me,indicatingtlle fbrInationOfaligand-basedperoxylradicalMe-tpa-CH200・generatedbytllereactionof Me-tpa-CH2･witllO2・OnepossiblepathwayfbrfUrtherreactionsinvolvestllefbmationof4ａｎｄ ５whiCllareresponsiblefbrthcfblTnationofMc-tpa-COO-andMe-tpa-CH20HTheperoxo ligandsin4and5areconvertedtoaligand-basedaldehydebyeitllerhomolysisorheterolysisof theO-Obondanddisproportionationofthealdellydegivescarboxylateandalkoxideviathe
Canni冗冗amreaction．
学位論文要旨
A1iphaticC-Hbondfimctionalizationbyvanousmetal-activeoxygenspeciesMm/Onsuchas
superoxo，peroxo，higdl-valentbis(J【上ＯＸＯ)dimetalspecies，etc、isofgrcatimportancefbr
understandingthereactionmecllanisnlsoflnetalloenzymesandutilizingmetalcomplexeSas
oxidationcatalysts・Inbiologicalsystems，O2-activatingmetalloenzymessucllasmethane
monooxygenase(ＭＭＯ）catalyzehydroxylationoflnethanetogivecolrespondingmethanol，
wherereductiveactivationofanO21no1ecule(dioxygen(02)弓superoxo(02-)弓peroxo(022~）
→ＯＸＯ(202~))ismducedbyoxidativeadditiontothetransitionmetalcentcr(s),andhigdl-valent bis仏ＯＸＯ)dimetalspeciesarepostulatedaspotentialoxidants(Schemel).Avarietyofsyntlletic lligll-valentbis似ＯＸＯ)dilnetal
MMOH-PcomplexesofFeandＣｕｈａｖｅ （｣(よperoxO)diiron(1Ⅱ）
becndevelopedandtheyCH4＋０２＋２Ｈ＋＋２e￣￣ＣＨ３０Ｈ＋H20
MMOH-Q
providedchemicalbasisｆｂｒ ｂｉｓ砂ＯＸＯ)diiron(１V）
understandingofstructuraland
Schemel･ReactioncatalyzedbyMMOandobservedintennediates．
vanousspectroscopicproperties,andreactivitiesofthelligdl-valentbis(ﾉﾙＯＸＯ)dilnetalcores、
Recently,suchlligd1-valentbis砂ＯＸＯ)dimetalchelnistryhasbeenextendedtoNiandCo complexes､Thecolnpansonoftllereactivityfbrthebis砂ＯＸＯ)dimetalcomplexeswithdifferent metalionsandligandsaffbrdsfUrtllerunderstandingoftlleC-HbondactivationmeC11amsm､In
tlliscontext，ａbis似OXO)dinickel(111）complex［Ni2(O)2(Me3-tpa)2]2＋（ZMe3~tpa，Me3-tpa＝
tris(6-methyl-2-pyridylmethyl)amine)hasbeenreportedinourlaboratory,wlliC11showsaliphatic C-Hbondactivationreactivitytogiveligand-basedalcoholandcarboxylate・Thatismsharp contrasttotllereactivityofabis砂OXO)dicopper(111）complex［Cu2(O)2(Me2-tpa)2]2＋（Zcu，
Me2-tpa＝bis(6-Inetllyl-2-pyridylnletllyl)(Z-pyridyllnetllyl)amine)wlliC11iscapableofoxidative 八Ｍcalkylationofthesupportingligand､Thus,itisobvioustllattllemetalionplaysanimportant loleintllealiphaticC-Hbondactivationoftllelligll-valentbis(ﾉﾙＯＸＯ)dimetalcolnplexes・
A1tllougdlanumberofbis(ﾉﾙoxo)dilnetal(111）complexeshavebeenshowntobecapableof aliphaticligandhydroxylationaswellaslVnealkylation,mecllanisticdetailsoftllefbnnation processfbrtheligand-basedcarboxylateunderO2havenotbeenreported
lntllisdissertation,wereportthattllereactionof[Ni2(OH)2(Me2-tpa)2]2十(1)withH202under O2causestheoxidationofametllylenegroupOfMe2-tpaligandtogiveamMeallKylatedligand andoxidationofalnetllylgrouptoaffbrdligand-basedcarboxylateandalcoholasfinaloxidation products､Aseriesoftllesequentialreactionintermediatesploducedmtheoxidationpatllways,ａ bis(J［んOXO)dinickel(111)，［Ni2(O)2(Me2-tpa)2]2十(2),ａbis(ﾉﾙsuperoxo)dimC1Kel(Ⅱ)，［Ni2(02)2(Me2 -tpa)2]2＋(3)，ａ(」【卜hydroxo)似alkylperoxo)diniCkel(11)，［Ni2(OH)(Me2-tpa)(Me-tpa-CH200)]2＋
(4),andabis(１(〃alkylperoxo)dinickel(11)complex,[Ni2(Me-tpa-CH200)2]2+(5),wasisolatedand cllaracterizedbyvarlouspllysicocllelnicallneasurelnentsincludingX-raycrystallographyand theiroxidationmechanisrnswereinvestigated．
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FormationandCharacterizationoftlleReactiveIntermediates･Ｔｈｅcomplex [Ni2(O)2(Me2-tpa)2]2+(2)wasobtainedbythedisproportionationof3mtlleabsenceofH202at
４０°Ｃ,becauselligdlreactivityof2towardH2021eadstofiJrtherreactiontogive3intllereaCtion oflwithH202・ZhasacentrosynnetricNi'''(ﾉﾋﾞﾙO)2Ni''I
corewitlltetradentateN-donorsoftlleMe2-tpa(Figurel)，
where2-pyridylmetl1ylsideannsareintlleequatorial positionsasfbundfbracolTesponding bisO卜OXO)dicopper(111）coInplex，［Cu2(O)2(Me2-tpa)2]2＋
(2Ｃｕ)mleaverageNi~NaxiaIbOnddistance(2.285Ａ)is
substantiallyshortertllantllatofZQI(2.515Ａ).Thelong axialbondsin2culnaybeascribedtoad8electron
,ﾎﾞﾘ藪L､≦
露,･･髄configuration，wllichtendstoadoptasquareplaneｒＦｉｇｕｒｅｌ・ORTEPdiagram（５０％
stm…ItMson･ted…MvemgoNi-OmdNLN璃翠iiy).錨ハIN蝿雌
bonddistances(1.852and2.130Ａ)ofZarecomparablelMrogcnatomsareomittedfbr
clarity
totllosem［Ni2(O)2(Me3-tpa)2]2十（ZMe3~tpa）（1.871ａｎｄ
2.143Ａ)However,theＮｉ…NiseparationandtlleNLN2bonddistance(2.796(1)and1.942(4)Ａ）
ofthein-planepyridylgroupinZissubstantiallyshortertllanthecorrespondingbonddistances (2.924(1)ａｎｄｚ.045(9)Ａ)in2Me3~tpa,intllelatterofwllichtlle6-metllylglouppreventsaclose approachoftllepyridylgro叩toamckelatombystericrequlrement、TYlein-plane 6-Inetllylpyridylgro叩ＳｏｆＺＭｅ３~tpafiDrlnahydrophobiccavityaroundaNiIII(ﾉﾙO)ZNiII'core，
WhichhasasignificantinfluenceontllereactivitywithＨ202（videinfia).Theelectronic spectmnofZshowsanintensebandat376nm(ど＝cα､６０００Ｍ~1cmｱ')inacetomtrileat-40oC，
similartotllatof2Me3~tp2(ﾉ１，，，ｍ＝394,1,,ｓ＝cα､４０００Ｍ-1cm-1).Suchintenseabsorptionbands havealsobeenobservedfbrfive-coordmatebisOJ-oxo)dinickel(111）colnplexescontaining tridentateN-donorligands（ﾉ１m“＝４０４～４１４，m)．Thesebandshavebeenassignedas
O2--to-Ni(111)chargctransfertransition(LMCT:(Gg＋dx2-h+))→(dxy(-)－Gm*))onthebasis
oftheoreticalcalculationsThereisatrendinCTtransitionenergies;CTtransitionenergieSoftlle
six-coordinatecolnplexes(Zand2M~tpa)arelligherthantlloseoftllefive-coordinatecomplexes
suchas[Ni2(O)2⑰Mc3)2](ﾉ１m`zx＝４１０，，，ｅ＝４２００Ｍ~1ｃｍ~').Tllismaybeattributabletoan
incrｅａｓｅｏｆｄｏｒｂｉｔａｌｅｎｅｒｇｙｄｕｅｔｏｔｌｌｅｉncreasedcoordinationnumberfiPoｍｆｉｖｅｔｏｓｉｘ (dinlimshingtheLewisacidityofNi(111)centers).Inaddition,theCTtransitionenergyof2is
higherthanthatof2Me3~tpa・TllisisalsoascribedtoastrongerelectrondOnationofMe2-tpawllich
lncreasesdorbitalenergycomparedtotllatofMe3-tpa､Tllisiss叩portedbytlleshorterNi-N2 bonddistance(1.942(4)Ａ)ofthein-planepyridylgroupm2relativetothecolrespondmgNi-N2 bonddistance(2.045(9)Ａ)oftllein-plane6-Inetllylpyridylgro叩in2Me3~tpa
Thecomplex［Ni2(02)2(Me2-tpa)2]2＋（３）hasacentrosynunetricNi''(ﾉﾙ00)2Nincorewitll
tetradentateN-dOnorsofthｅＭｅ２－ｔｐａａｓｆｂｕｎｄｆｂｒ
[Ni2(02)2(Me3-tpa)2]2+(３Ｍ~tpa).TheO-Obonddistanceof ３（L338(3)Ａ)iscon1parabletotllatof3Me3~tpa(1.345(6) A).ESI-TOF/MSspectnmnofacrystallinesampleof3in acetone/acetonitrileat-70oCshowedasignal colrespondmgtoamonomeric［Ni(02)(Me2-tpa)]+，
suggestingtllat3candissociateintoamonolnerinsolution、
However,thereisapossibilitytllattlledissociationoccurs
onlyundertlleESI-TOF/MSconditions・Inordertoclariか －－’￣－－－－－－一一…－－－.～…ニーユーユー…LﾕﾝFigure2・ORTEPdiagram（５０％
wl1ether3dissociatesintoaInonoInerinsolution，probability）ｏｆｔｈｅ［Ni2(Me-tpa
‐CH200)2]2＋ｃａｔｉｏｎｉｎ５－(BPh4)2．
electronicandEPRspectraweremcasured・ThefiJ11IMrogenatomsareomittedfbr characterizationofSinsolutionandsolidstateswithc'arity・
varlousspectroscopicmetllodsshowedtllatdimerstruclurerelnainsintactmsolutionstateが
Itisnotedtllattllerlnaldecompositionof3attlletemperatureabove-20oCgavealigand-based alk:ylperoxocomplex[Ni2(OH)(Me2-tpa)(Me-tpa-CH200)]2+(4),WllichisineqUilibriulnwitlll
and[Ni2(Me-tpa-CH200)2]2+(5),altlloughtheequilibriumliesintlleleftside(４÷１＋5).Tlle
complex5canbealsopreparedbytllereactionoflwitllexcessH202at20oCT11ecrystal structureof4consistsoftwoNi(11）centerslinkedbyahydroxobridgeinonesideandan alkylperoxobridgeintheotllerside,andthelatterofWllichisaligand-basedperoxidederived fionltlleoxidationofoneofthelnetllylgroupsintlleMe2-tpaligand・Tllecrystalstructureof5
hasaNiⅡ(JLJCOR)ZNiIIcoremWllichoneoftllemetllylgroupsofeachMe2-tpaligandisoxidized
toaligand-basedperoxideandtlleresultmgtwoperoxideslinktwonickel(11)ions(Figure2).TIle peroxidesseemtobestabilizedbytllefbrnlationoftllesixmemberedchelateringsandbridges，
TheO-ObonddistanceofL458(4)Ain5issimilartothatof4(1.462(6)Ａ).Complex4and5 arenovelexaml)lesofstructurallycharacterizedreactioninterlnediatesisolatedduringtlle
oxidationreactions．
-48-
ReactMtyoftlleIntermediates・Therlnaldecolnpositionof2underN2generatesan JVLdealkylatedligandandaligand-couplingdimerMe-tpa-CH2-CH2-tpa-Me､Thefbmationof Me-tpa-CH2-CHZ-tpa-Mesuggeststllataligand-basedradicalMe-tpa-CH2・isgeneratedasa reactionintennediateproducedpresulnablybyH-atomabstractionbytlleoxogroupIsotope labelingexperilnentslwealedtllatintraInolecularcouplingoccUrs（Figure3)．Incontrast，
decompositionof2and3intllepresenceofO2gavealigand-basedcarboxylateMe-tpa厚ＣＯＯ￣
andalcoholMe-tpa厚CH20HmsteadofMe-tpa負CH2-CH2-tpa-Me,indicatingtllefbrlnationofa ligand-basedperoxylradicalMe-tpa-CH200･generatedbytllereactionofMe-tpa-CH2･witllO2．
OnepossiblepatllwayfiDrfUrtherreactions involvesthefbmationｏｆ４ａｎｄ５ｄｅｒｉｖｅｄ Ｂｏｍ３ｗｈｉｃｈａｒｅｒｅｓponsiblefbrtlle fbmlationofMe-tｐａ－ＣＯＯ￣and Me-tpa-CH20H．Isotopelabeling experinlentsrevealedtllattlleirfbnnation processinvolvesthefbllowiilgsteps:１)tlle alkylperoxideligandsof4and5canbe convertedtoaligand-basedaldehydeby eitllerhomolysisorheterolysisoftheO-O bond,２）oxygenoftllealdellydecanbe exchangedwithH20viathefbnnationof aceta１，３）disproportionationofthe aldellydegivescarboxylateandalkoxide
viatheCannizzaroreactionStudiesontlle conversionof3to4via2andtlletllermal
decompositionof5providetllefirst detailedfbmationprocessoftlle ligand-basedcarboxylate、
RelationMweenReactMtyand Structures、ThereactivityofZtoward
pIN12(O)2(Me2-tpa)212.:53％
■INi2(O)2(d1-Me2rlpa)2f,:47％
□Me-tpa-CH2-CH2~tpa-Me:54％■dhFMe-tpa-CH2rCH2Ftpa-Me:46％
(a） (b）
Ⅲ
Ⅲ lⅢ.＿Ｓｍ
Ｓｉｍ．393
llllll
lIlll，
lUI
390３９２３９４３９６３９８４００６３２６３４６３６６３８６４０６４２ ｍなｍ/２
Figure3・ESI-TOF/MSspectraof(a)themixtureof
[Ni2(Oﾙ(Me2-tpa)2]2＋ａｎｄ［Ni2(O)2(cli-Me2-tpa)2]2＋in
acetonitrileat-40oC(relativeratio＝５３：４７),and(b）
couplingdimmersrccoveredafterthermal decompositionatroomtemperature(relativemtioof Me-tpa-CH2-CH2-tpa-MeandcL-Me-tpa-CH2-CH2 -tpa-Me＝５４：４６.ＮＯＣ！i-Me-tpa厚CH2-CH2-tpa-Meis detected)．
２ ２期０３.tpa
Figure4･Comparisonofspace-fillingmodelsfbrthe bis(〃oxo)dinickel(Ⅲ）complexes2and2Me3-tpa H202isquitedifferentffomthatof、1s(〃oxo)dlnlcKel(Ⅲ）comPlexeszandZ……。
（nickel:yellow;oxygen:１ｃｄ；nitrogen:blUe；Carbon：
[Ni2(O)2(Me3-tpa)2]2＋（ZMe3~tpa)．Unlikegray;hydrogen:cyan)．
2M日~tpa,complex2couldnotbeobtainedbyadirectreactionof[Ni2(OH)2(Me2-tpa)2]2+(1)witll
H202,sinccZisextremelIyreactivewitllH202toproduceS,T11isdifferentialreactivityseemsto
beattributabletotllestructuralfeaturesof2andZMe3-tpa(Figure4).Zhasaspacearoundtlle
Ni､('z卜O)ZNiIIIcorefbraccessofH202，whereasthereisnotenoughspacearoundthe NiII'(ﾉﾙO)2NiIIIcorem2Mc3~tpa・Thus,thein-plane6-metllylpyridylgroupsm2M小tpasignificantly
suppresstllereactivitywitllH202bythestereochelnicaleffect・
nleC-Hbondactivationoftllecoordmatedligandsinbis仏ＯＸＯ)dimetal(111)colnplexesis closelyrelatedtotllestructureandtheC-Hbondstrength2canoxidizebotllmetllyleneand methylgroups・Aballandstickmodelof2suggeststllattlleOox｡…Hdistancesfbrtllenletllyl groupsare２．２９－２．８５Ａdependingontlleorientationoftllehydrogenatonlsofthemelllyl
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Figures・Ballandstickmodesof(a)２M画~tpIl,(b)２ａｎｄ(c)ZcushowingtheC…0.ｘｏａｎｄＨ…Ooxo distances(A)closetotlleoxogroups､IMrogenatomswereplacedatthecalculatedpositionsnle
C-HbonddislancesaresettoO95A．
groupsandtllosefbrtllemethylenegroupsare2.59-2.70Ａ(Figure5b).Altlloughthehydrogens ofthemetllylgro叩scanapproachmorecloselytotlleoxogroups,tlleoxidationoftllemetllylene groupslnaybeattributabletoweakerC-Hbondenergyoftllemetllylenegroups・Asilnilar jMealkylationhasalsobeenobservedfbrthecolTespondmgcoppercomplex [Cu2(O)2(MC2-tpa)2]2+(2Cl),wherenooxidationofthelnetllylgroupWasdetected・Aballand stickmodelof2curevealstllattheOox｡…Hdistancesfbrtlleaxialmetllylgroups(2.75-3.34Ａ）
arelongerthantllosem2asshowninFigure5c・Thislongerdistancein2cumaybeascribedto
d8electronconfigurationwllichtendstoadoptasquare-planargeometly・Thustllehydrogen
atomsoftllemethylgroupsin2canapproachmorecloselytotheoxogroupcomparedtolllosein
2cuandtllisseelnstoberesponsiblefbrtlleparalleloxidationoftllemetllylandthemetllylene
gro叩s・Incontrast,selectiveoxidationoftllelnetllylgroupwasobservedfbr21M~tpa(onlyatrace aInountoflVnealjylationwasdetected),wllichseelnstobeduetotlleproxilnityeffectofthe in-planemethylgroupm2Me3~tpa(Oox｡…Ｈ＝2,17‐2.72A)asshownmFigure5a・
ThefindmgsinthisdissertationprovideanimportantbasisfbrchemistryofaliphaticC-Hbond fimctionaliZationbytllehigh-valentbis砂ＯＸＯ)dimetalcomplexes．
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