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Formic acid yog ib qho ntawm cov neeg sib tw zoo tshaj plaws rau kev khaws cia cov kua hydrogen ntev. Ntawm no peb nthuav qhia cov ruthenium clamp complexes tshiab nrog cov mis dav dav [RuHCl(POP)(PPh3)] siv cov khoom lag luam lossis yooj yim synthesized xanthos-type tridentate POP clamp ligands. Peb siv cov complexes no los dehydrogenate formic acid los tsim CO2 thiab H2 nyob rau hauv qhov tsis muaj zog, tsis muaj reflux siv cov kua ionic BMIM OAc (1-butyl-3-methylimidazolium acetate) ua cov kuab tshuaj. Los ntawm qhov pom ntawm qhov zaus hloov pauv siab tshaj plaws, cov catalyst zoo tshaj plaws yog [RuHCl(xantphos)(PPh3)]Ru-1 complex paub hauv cov ntaub ntawv, uas muaj qhov zaus hloov pauv siab tshaj plaws ntawm 4525 h-1 ntawm 90 ° C rau 10 feeb. Tus nqi hloov pauv tom qab yog 74%, thiab kev hloov pauv tau ua tiav hauv 3 teev (> 98%). Ntawm qhov tod tes, tus catalyst nrog qhov kev ua tau zoo tshaj plaws, qhov tshiab [RuHCl(iPr-dbfphos)(PPh3)]Ru-2 complex, txhawb kev hloov pauv tiav hauv 1 teev, ua rau muaj qhov hloov pauv tag nrho ntawm 1009 h-1. Tsis tas li ntawd, kev ua haujlwm catalytic kuj tau pom ntawm qhov kub txog li 60 ° C. Hauv theem roj, tsuas yog CO2 thiab H2 tau pom; CO tsis tau kuaj pom. High-resolution mass spectrometry qhia tau tias muaj N-heterocyclic carbene complexes hauv cov tshuaj sib xyaw.
Qhov kev loj hlob ntawm kev lag luam ntawm lub zog rov ua dua tshiab thiab nws qhov kev hloov pauv tau ua rau muaj kev xav tau rau cov thev naus laus zis khaws cia hluav taws xob hauv kev lag luam hauv lub zog, thermal, kev lag luam thiab kev thauj mus los1,2. Hydrogen yog suav tias yog ib qho ntawm cov khoom siv hluav taws xob muaj ntau tshaj plaws3, thiab cov khoom siv hydrogen organic kua (LOHCs) tsis ntev los no tau dhau los ua qhov tseem ceeb ntawm kev tshawb fawb, muab cov lus cog tseg ntawm kev khaws cia hydrogen hauv daim ntawv yooj yim ua tiav yam tsis muaj teeb meem cuam tshuam nrog kev nias lossis cryogenic technologies4. ,5,6. Vim lawv cov khoom siv lub cev, ntau ntawm cov khoom siv thauj mus los uas twb muaj lawm rau roj av thiab lwm yam roj kua tuaj yeem siv los thauj LOHC7,8. Cov khoom siv lub cev ntawm formic acid (FA) ua rau nws yog tus neeg sib tw zoo rau kev khaws cia hydrogen nrog cov ntsiab lus hydrogen ntawm 4.4%9,10. Txawm li cas los xij, cov txheej txheem catalytic luam tawm rau formic acid dehydrogenation feem ntau xav tau kev siv cov kuab tshuaj organic volatile, dej lossis ntshiab formic acid,11,12,13,14 uas yuav tsum tau siv cov txheej txheem sib cais cov kuab tshuaj xws li condensation, uas tuaj yeem ua rau muaj teeb meem hauv cov neeg siv khoom siv. daim ntawv thov, ntxiv load. Qhov teeb meem no tuaj yeem kov yeej los ntawm kev siv cov kuab tshuaj uas muaj qhov siab tsis tseem ceeb, xws li cov kua ionic. Yav dhau los, peb pawg neeg ua haujlwm tau qhia tias cov kua ionic butylmethylimidazolium acetate (BMIM OAc) yog cov kuab tshuaj tsim nyog hauv qhov kev tshuaj tiv thaiv no siv cov khoom siv kho Ru-PNP Ru-MACHO hom 15 uas muaj nyob hauv khw. Piv txwv li, peb tau ua qauv qhia FA dehydrogenation hauv lub kaw lus ntws tas mus li siv BMIM OAc, ua tiav TON ntau dua 18,000,000 ntawm 95 ° C. Txawm hais tias qee lub kaw lus tau ua tiav TON siab yav dhau los, ntau lub tau vam khom cov kuab tshuaj organic volatile (xws li THF lossis DMF) lossis cov khoom siv ntxiv (xws li cov hauv paus). Qhov sib piv, peb txoj haujlwm siv cov kua ionic tsis volatile (ILs) thiab tsis muaj cov khoom ntxiv.
Hazari thiab Bernskoetter tau tshaj tawm txog kev dehydrogenation ntawm formic acid (FA) ntawm 80 ° C siv Fe-PNP catalyst nyob rau hauv qhov muaj dioxane thiab LiBF4, ua tiav tus lej tig rov qab zoo kawg nkaus (TON) ntawm kwv yees li 1,000,00016. Laurenci siv Ru (II) - complex catalyst TPPPTS hauv lub kaw lus FA dehydrogenation tas mus li. Txoj kev no ua rau yuav luag tiav FA dehydrogenation nrog me ntsis cov cim ntawm CO pom ntawm 80 ° C17. Txhawm rau kom nce qib ntxiv rau daim teb no, Pidko tau ua pov thawj txog kev dehydrogenation ntawm FA siv Ru-PNP clamp catalysts hauv DMF / DBU thiab DMF / NHex₃ sib xyaw, ua tiav TON tus nqi ntawm 310,000 txog 706,500 ntawm 90 ° C18. Hull, Himeda thiab Fujita tau kawm txog binuclear Ir complex catalyst uas KHCO3 thiab H2SO4 tau txi, hloov pauv CO2 hydrogenation thiab FA dehydrogenation. Lawv cov tshuab tau ua tiav TONs ntau dua 3,500,000 thiab 308,000 feem rau hydrogenation ntawm 30 ° C, CO2 / H2 (1: 1), 1 bar siab thiab rau dehydrogenation ntawm 60 thiab 90 ° C19. Sponholz, Junge thiab Beller tau tsim ib qho Mn-PNP complex rau kev hloov pauv CO2 hydrogenation thiab FA dehydrogenation ntawm 90 ° C20.
Ntawm no peb siv txoj hauv kev IL, tab sis es tsis txhob siv Ru-PNPs, peb tau tshawb nrhiav kev siv cov catalysts Ru-POP, uas peb txoj kev paub tsis tau ua pov thawj ua ntej hauv qhov no.
Vim lawv txoj kev sib txuas hlau-ligand zoo heev (MLC), amino-PNP clamp complexes raws li Noyori-hom tswv yim nrog kev sib cuam tshuam cov pab pawg amino ua haujlwm theem nrab 21 (xws li Ru-MACHO-BH) feem ntau yog nrov zuj zus hauv qee qhov kev ua haujlwm me me. Piv txwv nrov suav nrog CO22, hydrogenation ntawm alkenes thiab carbonyls, hloov hydrogenation23 thiab acceptorless dehydrogenation ntawm cawv24. Nws tau raug tshaj tawm tias N-methylation ntawm PNP clamp ligands tuaj yeem nres tag nrho cov catalyst activity25, uas tuaj yeem piav qhia los ntawm qhov tseeb tias amines ua haujlwm ua proton qhov chaw, uas yog qhov tseem ceeb thaum lub sijhawm catalytic siv MLC. Txawm li cas los xij, qhov sib txawv hauv formic acid dehydrogenation tau pom tsis ntev los no los ntawm Beller, qhov twg N-methylated Ru-PNP complexes tau qhia zoo dua catalytic dehydrogenation ntawm formic acid dua li lawv cov unmethylated counterparts26. Vim tias qhov qub complex tsis tuaj yeem koom nrog MLC los ntawm amino unit, qhov no qhia tau tias MLC, thiab yog li ntawd amino unit, yuav ua lub luag haujlwm tsis tseem ceeb hauv qee qhov kev hloov pauv (de) hydrogenation dua li qhov xav ua ntej.
Piv rau POP clamps, cov ruthenium complexes ntawm POP clamps tsis tau kawm txaus hauv thaj chaw no. POP ligands ib txwm siv rau hydroformylation, qhov twg lawv ua haujlwm ua chelating ligands es tsis yog lub kaum sab xis bidentate tom ntawm kwv yees li 120 ° rau clamping ligands, uas tau siv los ua kom zoo dua qhov kev xaiv rau cov khoom linear thiab branched27,28,29. Txij thaum ntawd los, Ru-POP complexes tsis tshua muaj siv hauv hydrogenation catalysis, tab sis piv txwv ntawm lawv cov haujlwm hauv kev hloov hydrogenation tau tshaj tawm yav dhau los30. Ntawm no peb qhia tau tias Ru-POP complex yog ib qho catalyst zoo rau dehydrogenation ntawm formic acid, lees paub Beller qhov kev tshawb pom tias cov amino unit hauv cov tshuaj Ru-PNP amine catalyst tsis tseem ceeb hauv qhov kev tshuaj tiv thaiv no.
Peb txoj kev tshawb fawb pib nrog kev tsim cov tshuaj catalysts nrog cov mis dav dav [RuHCl(POP)(PPh3)] (Daim Duab 1a). Txhawm rau hloov kho cov qauv steric thiab hluav taws xob, dibenzo[b,d]furan tau xaiv los ntawm cov khoom lag luam 4,6-bis(diisopropylphosphino) (Daim Duab 1b) 31. Cov tshuaj catalysts kawm hauv txoj haujlwm no tau tsim los ntawm kev siv txoj kev dav dav uas tsim los ntawm Whittlesey32, nrog rau kev siv [RuHCl(PPh3)3]•toluene33 adduct ua tus precursor. Sib tov cov hlau precursor thiab POP clamp ligand hauv THF nyob rau hauv cov xwm txheej anhydrous thiab anaerobic. Cov tshuaj tiv thaiv tau nrog los ntawm kev hloov xim tseem ceeb los ntawm xim av tsaus mus rau daj thiab muab cov khoom ntshiab tom qab 4 teev ntawm reflux lossis 72 teev ntawm reflux ntawm 40 ° C. Tom qab tshem tawm THF hauv vacuo thiab ntxuav ob zaug nrog hexane lossis diethyl ether, triphenylphosphine tau raug tshem tawm kom muab cov khoom ua hmoov daj hauv cov txiaj ntsig siab.
Kev tsim cov Ru-1 thiab Ru-2 complexes. a) Txoj kev tsim cov complexes. b) Cov qauv ntawm cov synthesized complex.
Ru-1 twb paub lawm los ntawm cov ntaub ntawv32, thiab cov yam ntxwv ntxiv tsom mus rau Ru-2. Lub 1H NMR spectrum ntawm Ru-2 tau lees paub qhov cis configuration ntawm lub phosphine atom hauv ligand ntawm hydride khub. Lub peak dt plot (Daim duab 2a) qhia 2JP-H coupling constants ntawm 28.6 thiab 22.0 Hz, uas nyob hauv qhov ntau ntawm cov ntawv ceeb toom yav dhau los32. Hauv hydrogen decoupled 31P {1H} spectrum (Daim duab 2b), 2JP-P coupling constant ntawm kwv yees li 27.6 Hz tau pom, lees paub tias ob qho tib si clamp ligand phosphines thiab PPh3 yog cis-cis. Tsis tas li ntawd, ATR-IR qhia txog tus yam ntxwv ruthenium-hydrogen stretching band ntawm 2054 cm-1. Rau kev piav qhia ntxiv txog cov qauv, Ru-2 complex tau crystallized los ntawm vapor diffusion ntawm chav tsev kub nrog zoo txaus rau kev tshawb fawb X-ray (Daim duab 3, Supplementary Table 1). Nws crystallizes nyob rau hauv lub triclinic system ntawm qhov chaw pawg P-1 nrog ib tug cocrystalline benzene unit ib chav tsev cell. Nws qhia txog lub dav P-Ru-P occlusal kaum ntawm 153.94 °, uas yog dav dua li 130 ° occlusal kaum ntawm bidentate DBFphos34. Ntawm 2.401 thiab 2.382 Å, qhov ntev ntawm Ru-PPOP bond ntev dua li Ru rau PPh3 bond ntev ntawm 2.232 Å, uas tej zaum yuav yog qhov tshwm sim ntawm lub dav backbone snack kaum ntawm DBFphos tshwm sim los ntawm nws lub hauv paus 5-ring. Lub geometry ntawm lub hlau chaw yog qhov tseem ceeb octahedral nrog lub O-Ru-PPh3 kaum ntawm 179.5 °. Kev sib koom tes H-Ru-Cl tsis yog linear tag nrho, nrog lub kaum ntawm kwv yees li 175 ° los ntawm triphenylphosphine ligand. Atomic nrug thiab bond ntev tau teev nyob rau hauv Rooj 1.
NMR spectrum ntawm Ru-2. a) Thaj chaw Hydride ntawm 1H NMR spectrum qhia lub teeb liab Ru-H dt. b) 31 P{1 H} NMR spectrum qhia cov teeb liab los ntawm triphenylphosphine (xiav) thiab POP ligand (ntsuab).
Cov qauv ntawm Ru-2. Cov ellipsoids thermal tau tso tawm nrog 70% qhov muaj feem. Rau qhov meej meej, cov cocrystalline benzene thiab hydrogen atoms ntawm cov pa roj carbon tau raug tshem tawm.
Txhawm rau ntsuam xyuas lub peev xwm ntawm cov complexes kom dehydrogenate formic acid, cov xwm txheej tshuaj tiv thaiv tau raug xaiv nyob rau hauv qab uas cov PNP-clamp complexes sib xws (piv txwv li, Ru-MACHO-BH) tau ua haujlwm heev15. Dehydrogenation ntawm 0.5 ml (13.25 mmol) formic acid siv 0.1 mol% (1000 ppm, 13 µmol) ruthenium complex Ru-1 lossis Ru-2 siv 1.0 ml (5.35 mmol) ionic kua (IL) BMIM OAc (rooj-duab) 2; Daim duab 4);
Yuav kom tau txais tus qauv, qhov kev tshuaj tiv thaiv tau ua thawj zaug siv cov khoom siv ua ntej [RuHCl(PPh3)3]·toluene. Qhov kev tshuaj tiv thaiv tau ua tiav ntawm qhov kub ntawm 60 txog 90 °C. Raws li kev soj ntsuam pom yooj yim, cov tshuaj tsis tuaj yeem yaj tag nrho hauv IL txawm tias muaj kev sib xyaw ntev ntawm qhov kub ntawm 90 °C, tab sis kev yaj tau tshwm sim tom qab kev qhia txog formic acid. Ntawm 90 °C, kev hloov pauv ntawm 56% (TOF = 3424 h-1) tau ua tiav hauv 10 feeb thawj zaug, thiab yuav luag muaj kev hloov pauv ntau (97%) tau ua tiav tom qab peb teev (nkag 1). Kev txo qhov kub mus rau 80 °C txo qhov kev hloov pauv los ntawm ntau dua ib nrab mus rau 24% tom qab 10 feeb (TOF = 1467 h-1, nkag 2), ntxiv txo nws mus rau 18% thiab 18% ntawm 70 °C thiab 60 °C, feem 6% (nkag 3 thiab 4). Hauv txhua qhov xwm txheej, tsis muaj lub sijhawm pib tshwm sim, qhia tias cov tshuaj catalyst yuav yog cov hom tshuaj reactive lossis tias kev hloov pauv ntawm cov hom tshuaj reactive sai dhau los nrhiav tau siv cov ntaub ntawv no.
Tom qab kev ntsuam xyuas cov khoom ua ntej, Ru-POP clamp complexes Ru-1 thiab Ru-2 tau siv nyob rau hauv tib qho xwm txheej. Ntawm 90 ° C, kev hloov pauv siab tau pom tam sim ntawd. Ru-1 tau ua tiav 74% kev hloov pauv hauv 10 feeb thawj zaug ntawm kev sim (TOFmax = 4525 h-1, nkag 5). Ru-2 tau qhia me ntsis tsawg dua tab sis ua haujlwm sib xws, txhawb nqa 60% kev hloov pauv hauv 10 feeb (TOFmax = 3669 h-1) thiab kev hloov pauv tag nrho hauv 60 feeb (> 99%) (nkag 9). Nws yog qhov tsim nyog tias Ru-2 zoo dua li cov hlau ua ntej thiab Ru-1 ntawm kev hloov pauv tag nrho. Yog li ntawd, thaum cov hlau ua ntej thiab Ru-1 muaj cov nqi TOF zoo sib xws ntawm kev ua tiav cov tshuaj tiv thaiv (330 h-1 thiab 333 h-1, feem), Ru-2 muaj TOF ntawm 1009 h-1.
Ru-1 thiab Ru-2 raug hloov pauv kub uas qhov kub tau maj mam txo qis hauv 10 ° C nce mus rau qhov tsawg kawg nkaus ntawm 60 ° C (Daim Duab 3). Yog tias ntawm 90 ° C lub complex qhia txog kev ua haujlwm tam sim ntawd, yuav luag tag nrho kev hloov pauv tshwm sim hauv ib teev, tom qab ntawd ntawm qhov kub qis dua qhov kev ua haujlwm poob qis heev. Kev hloov pauv ntawm Py-1 yog 14% thiab 23% tom qab 10 feeb ntawm 80 ° C thiab 70 ° C, feem, thiab tom qab 30 feeb nws nce mus rau 79% thiab 73% (nkag 6 thiab 7). Ob qho kev sim tau qhia txog tus nqi hloov pauv ntawm ≥90% hauv ob teev. Tus cwj pwm zoo sib xws tau pom rau Ru-2 (nkag 10 thiab 11). Qhov nthuav yog, Ru-1 tau me ntsis tseem ceeb thaum kawg ntawm kev tshuaj tiv thaiv ntawm 70 ° C nrog tag nrho TOF ntawm 315 h-1 piv rau 292 h-1 rau Ru-2 thiab 299 h-1 rau cov hlau precursor.
Qhov kub thiab txias txo qis mus rau 60 ° C ua rau tsis muaj kev hloov pauv pom thaum 30 feeb thawj zaug ntawm kev sim. Ru-1 tsis tshua muaj zog ntawm qhov kub qis tshaj plaws thaum pib ntawm kev sim thiab tom qab ntawd ua haujlwm ntau ntxiv, qhia txog qhov yuav tsum tau ua kom lub sijhawm ua haujlwm thaum lub sijhawm Ru-1 precatalyst hloov pauv mus ua hom catalytic. Txawm hais tias qhov no ua tau ntawm txhua qhov kub thiab txias, 10 feeb thaum pib ntawm kev sim tsis txaus los ntes lub sijhawm ua haujlwm ntawm qhov kub siab dua. Tus cwj pwm zoo sib xws tau pom rau Ru-2. Ntawm 70 thiab 60 ° C, tsis muaj kev hloov pauv tau pom thaum 10 feeb thawj zaug ntawm kev sim. Nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias hauv ob qho kev sim, cov pa roj carbon monoxide tsis tau pom hauv qhov txwv ntawm peb lub cuab yeej (<300 ppm), nrog H2 thiab CO2 yog cov khoom lag luam nkaus xwb uas tau pom.
Kev sib piv ntawm cov txiaj ntsig formic acid dehydrogenation tau txais yav dhau los hauv pawg ua haujlwm no, sawv cev rau lub xeev ntawm cov kos duab thiab siv Ru-PNP clamp complexes, qhia tau hais tias Ru-POP clamp tshiab synthesized muaj kev ua haujlwm zoo ib yam li nws cov PNP counterpart 15. Thaum clamp Lub PNP tau txais RPMs ntawm 500-1260 h-1 hauv kev sim ua ke, POP clamp tshiab tau txais TOFovertal tus nqi zoo sib xws ntawm 326 h-1, thiab TOFmax tus nqi ntawm Ru-1 thiab 1590 h-1 tau pom. feem, yog 1988 h-1 thiab 1590 h-1. Ru-2 yog 1 ntawm 80 ° C, Ru-1 yog 4525 h-1 thiab Ru-1 yog 3669 h-1 ntawm 90 ° C, feem.
Kev tshuaj ntsuam kub ntawm formic acid dehydrogenation siv Ru-1 thiab Ru-2 catalysts. Cov xwm txheej: 13 µmol catalyst, 0.5 ml (13.25 mmol) formic acid, 1.0 ml (5.35 mmol) BMIM OAc.
NMR yog siv los nkag siab txog cov txheej txheem ua haujlwm. Vim tias muaj qhov sib txawv tseem ceeb heev hauv 2JH-P ntawm hydride thiab phosphine ligands, qhov kev tsom mus rau txoj kev tshawb fawb no yog nyob rau ntawm hydride peak. Rau Ru-1, tus qauv dt ib txwm muaj ntawm chav hydrogenation tau pom thaum lub sijhawm 60 feeb thawj zaug ntawm dehydrogenation. Txawm hais tias muaj kev hloov pauv tseem ceeb ntawm −16.29 txog −13.35 ppm, nws cov kev sib txuas nrog phosphine yog 27.2 thiab 18.4 Hz, feem (Daim Duab 5, Peak A). Qhov no yog sib xws nrog tag nrho peb phosphines uas hydrogen ligand nyob hauv cis configuration thiab qhia tias ligand configuration ruaj khov me ntsis hauv IL rau kwv yees li ib teev nyob rau hauv cov xwm txheej ua haujlwm zoo tshaj plaws. Qhov kev hloov pauv downfield muaj zog yuav yog vim muaj kev tshem tawm cov chlorinated ligands thiab kev tsim cov acetyl-formic acid complexes sib xws, qhov tsim ntawm d3-MeCN complex hauv NMR tube, lossis kev tsim cov N-heterocycles sib xws. piav qhia. Carbene (NHC) complex. Thaum lub sijhawm dehydrogenation reaction, qhov muaj zog ntawm lub teeb liab no txuas ntxiv txo qis, thiab tom qab 180 feeb lub teeb liab tsis tau pom dua. Hloov chaw, ob lub teeb liab tshiab tau pom. Thawj qhov qhia txog tus qauv dd meej tshwm sim ntawm -6.4 ppm (peak B). Lub doublet muaj qhov sib txuas loj ntawm kwv yees li 130.4 Hz, qhia tias ib qho ntawm cov phosphine units tau tsiv mus rau hydrogen. Qhov no txhais tau tias POP clamp tau rov qab kho dua tshiab rau hauv κ2-P,P configuration. Qhov tshwm sim ntawm qhov complex no lig hauv catalysis yuav qhia tau tias hom tsiaj no ua rau txoj kev deactivation dhau sijhawm, tsim cov catalyst sink. Ntawm qhov tod tes, qhov kev hloov pauv tshuaj tsawg qhia tias nws yuav yog hom dihydrogenous15. Lub ncov tshiab thib ob nyob ntawm -17.5 ppm. Txawm hais tias nws qhov quav tsis paub, peb ntseeg tias nws yog triplet nrog qhov sib txuas me me ntawm 17.3 Hz, qhia tias cov hydrogen ligand tsuas yog khi rau phosphine ligand ntawm POP clamp, kuj qhia txog kev tso tawm ntawm triphenylphosphine (ncov C). Nws tuaj yeem hloov los ntawm lwm ligand, xws li ib pawg acetyl lossis NHC tsim nyob rau hauv situ los ntawm cov kua ionic. Kev sib cais ntawm PPh3 yog qhia ntxiv los ntawm ib qho muaj zog singlet ntawm -5.9 ppm. hauv 31P {1H} spectrum ntawm Ru-1 tom qab 180 feeb ntawm 90 ° C (saib cov ntaub ntawv ntxiv).
Thaj chaw Hydride ntawm 1H NMR spectrum ntawm Ru-1 thaum lub sijhawm dehydrogenation ntawm formic acid. Cov xwm txheej tshuaj tiv thaiv: 0.5 ml formic acid, 1.0 ml BMIM OAc, 13.0 µmol catalyst, 90 ° C. NMR tau coj los ntawm MeCN-d 3, 500 μl ntawm deuterated solvent, kwv yees li 10 μl ntawm cov tshuaj tiv thaiv sib xyaw.
Txhawm rau kom paub meej ntxiv txog qhov muaj cov tsiaj txhu hauv lub kaw lus catalytic, kev tshuaj xyuas qhov siab daws teeb meem loj (HRMS) ntawm Ru-1 tau ua tom qab txhaj tshuaj formic acid rau 10 feeb ntawm 90 ° C. Qhov no qhia txog qhov muaj cov tsiaj txhu tsis muaj chlorine ligand precatalyst hauv cov tshuaj sib xyaw. nrog rau ob lub NHC complexes, cov qauv tsim uas tau pom hauv Daim Duab 6. Cov spectrum HRMS sib xws tuaj yeem pom hauv Daim Duab Ntxiv 7.
Raws li cov ntaub ntawv no, peb xav kom muaj ib qho kev ua haujlwm hauv lub cev zoo ib yam li Beller tau hais, uas N-methylated PNP clamps ua rau tib qho kev ua haujlwm. Cov kev sim ntxiv tsis suav nrog cov kua ionic tsis tau qhia txog kev ua ub no, yog li nws txoj kev koom tes ncaj qha zoo li tsim nyog. Peb xav tias kev ua haujlwm ntawm Ru-1 thiab Ru-2 tshwm sim los ntawm chloride dissociation ua raws li qhov ua tau NHC ntxiv thiab triphenylphosphine dissociation (Scheme 1a). Qhov kev ua haujlwm no hauv txhua hom tsiaj tau pom yav dhau los siv HRMS. IL-acetate yog lub hauv paus Bronsted muaj zog dua li formic acid thiab tuaj yeem ua rau deprotonate tom kawg35. Peb xav tias thaum lub sijhawm catalytic cycle (Scheme 1b), cov hom A uas muaj NHC lossis PPh3 tau sib koom tes los ntawm formate los tsim cov hom B. Kev hloov kho dua tshiab ntawm cov complex no rau C thaum kawg ua rau muaj CO2 thiab trans-dihydrogen complex D. Kev protonation tom qab ntawm cov kua qaub rau hauv dihydro complex nrog cov acetic acid uas tau tsim ua ntej los tsim dihydro complex E zoo ib yam li cov kauj ruam tseem ceeb uas Beller tau hais siv N-methylated PNP clamp homologues. Tsis tas li ntawd, ib qho analogue ntawm cov complex EL = PPh3 tau synthesized ua ntej los ntawm kev sib xyaw stoichiometric siv Ru-1 hauv hydrogen huab cua tom qab rho tawm chloride nrog sodium ntsev. Kev tshem tawm ntawm hydrogen thiab kev sib koom tes ntawm formate muab A thiab ua tiav lub voj voog.
Ib txoj hauv kev rau qhov tshuaj tiv thaiv intrasphere ntawm formic acid dehydrogenation siv cov tshuaj kho Ru-POP Ru-1 tau raug npaj tseg.
Ib qho complex tshiab [RuHCl(iPr-dbfphos)(PPh3)] tau raug tsim ua ke. Lub complex tau piav qhia los ntawm NMR, ATRIR, EA thiab X-ray diffraction analysis ntawm cov siv lead ua ib leeg. Peb kuj tshaj tawm thawj zaug kev siv Ru-POP pincer complexes hauv dehydrogenation ntawm formic acid rau CO2 thiab H2. Txawm hais tias cov hlau precursor tau ua tiav cov haujlwm zoo sib xws (txog li 3424 h-1), lub complex tau mus txog qhov siab tshaj plaws ntawm kev hloov pauv mus txog 4525 h-1 ntawm 90 ° C. Ntxiv mus, ntawm 90 ° C, lub complex tshiab [RuHCl(iPr-dbfphos)(PPh3)] tau ua tiav tag nrho lub sijhawm ntawm kev ya (1009 h-1) kom ua tiav formic acid dehydrogenation, uas yog siab dua li ntawm cov hlau precursor (330 h-1). thiab lub complex tau tshaj tawm ua ntej [RuHCl(xantphos)(PPh3)] (333 h-1). Nyob rau hauv cov xwm txheej zoo sib xws, qhov ua tau zoo ntawm catalytic zoo ib yam li Ru-PNP clamp complex. Cov ntaub ntawv HRMS qhia txog qhov muaj carbene complex hauv cov tshuaj sib xyaw, txawm tias muaj me me xwb. Tam sim no peb tab tom kawm txog cov teebmeem catalytic ntawm carbene complexes.
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