A cobalt pincer complex bearing both P and C-stereogenic centers has been designed and synthesized,allowing for the development of the first cobalt-catalyzed asymmetric hydrogenation of quinoxalines under relatively m...A cobalt pincer complex bearing both P and C-stereogenic centers has been designed and synthesized,allowing for the development of the first cobalt-catalyzed asymmetric hydrogenation of quinoxalines under relatively mild conditions.Valuable chiral 1,2,3,4-tetrahydroquinoxalines could be obtained with high yields and excellent enantioselectivities(35 examples,up to>99%ee).展开更多
A convenient colorimetric approach for visual detection of melamine in raw milk was realized by using gold nanoparticles(AuNPs)stabilized by an unsymmetrical terpyridyl zinc complex with a thymine fragment at one term...A convenient colorimetric approach for visual detection of melamine in raw milk was realized by using gold nanoparticles(AuNPs)stabilized by an unsymmetrical terpyridyl zinc complex with a thymine fragment at one terminal and a quaternary ammonium salt at the other.Even without pre-addition of melamine or relative additives,obvious color change from red to blue was observed by naked eye in the presence of trace amount of melamine,which was attributed to the alternation of aggregation state of AuNPs caused by the selective binding between the thymine fragment and melamine via triple hydrogenbonding interactions.Remarkably,the detection limit for melamine was as low as 2.4 ppb,providing a highly sensitive and efficient approach for the visual detection of melamine.展开更多
A nonsymmetrical PNN pincer ligand[6-(^(t)Bu_(2)PNH)C_(5)H_(4)N-2-(3-Mes)C_(3)H_(2)N_(2)]and its corresponding cobalt-N_(2)complex were synthesized and characterized.By the stoichiometric reaction of the PNN ligand li...A nonsymmetrical PNN pincer ligand[6-(^(t)Bu_(2)PNH)C_(5)H_(4)N-2-(3-Mes)C_(3)H_(2)N_(2)]and its corresponding cobalt-N_(2)complex were synthesized and characterized.By the stoichiometric reaction of the PNN ligand lithium salt with CoCl_(2),the complex 3,(PNN)CoCl,was obtained.Then,reduction of 3 with NaBHEt3under a dinitrogen atmosphere yielded complex 5,(PNN)Co(Ⅰ)(η^(1)-N_(2)).Single-crystal X-ray analysis,IR spectrum,and DFT calculations revealed that the dinitrogen in 5 was only weakly reduced by the cobalt center.The reactions of 5 with carbon monoxide and 2,6-dimethylphenyl isocyanide gave carbonyl and isocyanide complexes 6 and 7 with the release of N_(2),respectively.Furthermore,these cobalt complexes,especially complex 5,demonstrated the capacity to convert dinitrogen to N(TMS)_(3)with moderate efficiency.展开更多
The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst l...The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is readily scaled up to 2 mmol scale without any loss in activity and enantioselectivity. Density functional theory(DFT)calculations have been performed to better understand the reaction mechanism and to explain the stereochemical outcome of the reactions.展开更多
Platinum complexes of the diimino/carbazolyl NNN pincer ligand have been prepared and characterized.Cyclometallation of the mesityl substituent was observed to occur unexpectedly easily in(NNN)PtOTf,which also catalyz...Platinum complexes of the diimino/carbazolyl NNN pincer ligand have been prepared and characterized.Cyclometallation of the mesityl substituent was observed to occur unexpectedly easily in(NNN)PtOTf,which also catalyzed cyclometallation in(NNN)PtMe.Introduction Pincer complexes have gained in popularity in part because they offer a robust and well-defined framework for study of elementary reactions at transition metal centers.1 Our group,among many others,has been particularly attracted to pincer ligands based on the diarylamido central unit with ortho-positioned side donors(Chart 1).展开更多
Iron catalysis is attractive for organic synthesis because iron is inexpensive,abundant,and non-toxic.To control the activity and stability of an iron center,a large number of iron pincer complexes have been synthesiz...Iron catalysis is attractive for organic synthesis because iron is inexpensive,abundant,and non-toxic.To control the activity and stability of an iron center,a large number of iron pincer complexes have been synthesized.Many such complexes exhibit excellent catalytic activity in a number of important organic reactions such as hydrogenation,hydrosilylation,dehydrogenation,and carbon-carbon bond forming reactions.In this review,recent examples of representative iron pincer catalysts are presented.展开更多
This work reports the first example of mono-nuclear Cu pincers with SNS ligation acting as electrocatalyst precursors for the electrochemical conversion of carbon dioxide to CO and H_(2)in protic organic media.
Palladium POCOP-pincer hydride complexes[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdH(R=tBu,2a;R=^(i)Pr,2b;R=^(c)Pe,2c,^(c)Pe=cyclopentyl)have been synthesized from[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCl(1a-c)and LiAlH_(4) or LiBEt_(3)H...Palladium POCOP-pincer hydride complexes[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdH(R=tBu,2a;R=^(i)Pr,2b;R=^(c)Pe,2c,^(c)Pe=cyclopentyl)have been synthesized from[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCl(1a-c)and LiAlH_(4) or LiBEt_(3)H.These hydride complexes react with phenylacetylene to afford H2,[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCuCPh(3a-c)and a small amount of styrene.When the R groups are isopropyl groups,a second palladium species is generated,and it has been identified as an alkenyl complex(E)-[2,6-(^(i)Pr_(2)PO)_(2)C_(6)H_(3)]PdCHvCHPh(4b).Mechanistic studies have shown that decomposition of these palladium pincer complexes and related palladium methyl complexes[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCH_(3)(5a-c)occurs at room temperature in the presence of H_(2)(1 atm or lower),resulting in the leaching of palladium particles.These particles have been shown to catalyze the hydrogenation of phenylacetylene and diphenylacetylene to their alkene and alkane products.A mechanism for the formation of palladium particles has been proposed.The structures of 1a,1c,2a,2c,3a,4b and 5b have been studied by X-ray crystallography.展开更多
This work describes the efficacy of[PNP]PdCl(1a),where[PNP]^(-)=bis(2-diphenylphosphinophenyl)amide,as a catalyst precursor for C_(sp)-C_(sp2) bond-forming cross-coupling reactions of terminal alkynes with aryl halide...This work describes the efficacy of[PNP]PdCl(1a),where[PNP]^(-)=bis(2-diphenylphosphinophenyl)amide,as a catalyst precursor for C_(sp)-C_(sp2) bond-forming cross-coupling reactions of terminal alkynes with aryl halides in the presence of copper bromide and aliphatic amines in ethereal solutions under mild conditions.This catalysis is compatible with acetylenes that are alkyl,alkenyl,(hetero)aryl,or silyl substituted and aryl iodides or bromides that are electronically activated,neutral,or deactivated.The low reaction constants of 0.82(6)and 0.97(7)obtained from Hammett plots of competitive reactions employing electronically distinct aryl iodides and terminal alkynes,respectively,are likely suggestive of irrelevance of the rate-determining step in these catalytic transformations to oxidative addition of aryl halides or generation of mono-substituted acetylides.In sharp contrast,reactions employing a phosphorus-bound isopropyl derived 1b gave rather unsatisfactory results,highlighting a profound phosphorus substituent effect on this aryl alkynylation catalysis.展开更多
The hydroboration of alkenes catalyzed using an inexpensive and easily accessible Earth-abundant cobalt pincer complex based on a PN5P triazine backbone is reported.The presented protocol allows efficient anti-Markovn...The hydroboration of alkenes catalyzed using an inexpensive and easily accessible Earth-abundant cobalt pincer complex based on a PN5P triazine backbone is reported.The presented protocol allows efficient anti-Markovnikov functionalization of alkenes bearing a wide range of functional groups(unsaturated amines,carbonates,ethers,vinylarenes,vinylsilanes,and natural products)under mild conditions with high yields.Moreover,the presented procedure exhibits unique selectivity distinguishing vinylsilyl groups from other alkenyl or alkyne groups,leading to an interesting class of bifunctional compounds that have potential application in the synthesis of advanced materials.Their application potential was demonstrated by several model transformations.展开更多
We report a series of redox-active bis(pincer)Pd(II)complexes in which the redox active units are based on either a diarylamido or a carbazolide framework.Compounds 1 and 2 contain two full diarylamido/bis(pincer)PNP ...We report a series of redox-active bis(pincer)Pd(II)complexes in which the redox active units are based on either a diarylamido or a carbazolide framework.Compounds 1 and 2 contain two full diarylamido/bis(pincer)PNP units connected either via an Ar–O–Ar linker(1)or an Ar–Ar bond(2).Compound 3 is a fused bis(pincer)where the two PNP units share an aromatic ring.展开更多
Herein we report the application of a Co(II)PNN^(H) pincer catalyst system(PNN^(H)=2-(5-(t-butyl)-1Hpyrazol-3-yl)-6-(dialkylphosphinomethyl)pyridine)for the highly E-selective transfer semihydrogenation of internal di...Herein we report the application of a Co(II)PNN^(H) pincer catalyst system(PNN^(H)=2-(5-(t-butyl)-1Hpyrazol-3-yl)-6-(dialkylphosphinomethyl)pyridine)for the highly E-selective transfer semihydrogenation of internal diaryl alkynes using methanol and ammonia borane as hydrogen donors.The catalyst system is highly active(short reaction times,low Co concentration)and operates at very mild conditions(low temperature and transfer hydrogenation conditions).Spectroscopic and computational studies suggest that catalysis occurs via the Co(II)oxidation state,most likely with a Co(II)hydride as the key intermediate.Computational analysis of the reaction mechanism further rationalises the selective formation of E-alkenes and the absence of overreduction to produce alkanes.展开更多
Photoactive,octahedral transition metal complexes supported by rigid,multidentate ligand scaffolds have been successfully deployed for diverse photochemical processes.Challenges remain,however,in addressing deficienci...Photoactive,octahedral transition metal complexes supported by rigid,multidentate ligand scaffolds have been successfully deployed for diverse photochemical processes.Challenges remain,however,in addressing deficiencies in reaction scalability,selectivity,and media penetration.In this regard,the development of new materials with intense red or near-infrared(NIR)absorption is of great interest.Herein,we report the synthesis,structure,and spectroscopic characterization of air-stable,dicationic transition metal complexes[M(CNC)_(2)]^(2+)(M=Cr,Mn,and Fe)supported by bis(carbene)-amide CNC pincer ligands.Results show intense NIR absorption(ε_(max)≈10000 M^(−1) cm^(-1))with the metal-dependent peak maxima spanning the first and second NIR regions.Importantly,the lowest energy main NIR absorption in each complex is assigned to the ligand-to-metal charge-transfer(LMCT)transition from the amide-based non-bonding orbital to the three-centered N–M–Nπ-antibonding orbital.Broadly,our studies provide a blueprint for the design of intense NIR-absorbing metal complexes based on a parallel N–M–Nπ-bonding motif with flanking strong field carbene donors.展开更多
NNN pincer incorporated porous organic polymers(POPs)were prepared using a facile knitting method of pyridine based ligands via the Friedel–Crafts reaction.Ru-based molecular catalysts supported on the prepared POPs ...NNN pincer incorporated porous organic polymers(POPs)were prepared using a facile knitting method of pyridine based ligands via the Friedel–Crafts reaction.Ru-based molecular catalysts supported on the prepared POPs were implemented for catalytic CO_(2)hydrogenation into formate and methyl formate.In particular,a heterogeneous Ru/N-Me-3-bpp-POP catalyst exhibited the maximum catalytic conversion of CO_(2)into formate,with a turnover number(TON)of 1877,and into methyl formate with a TON of 2197.In addition,the stability of the Ru/N-Me-3-bpp-POP catalyst was demonstrated over five successive runs with a slight decrease in the catalytic efficiency,which may originate from Ru leaching.展开更多
Comprehensive Summary Terpyridine ligands have been applied as a class of unique ligands due to their rich coordination chemistry in the catalysis.Herein,we developed a new class of C_(2)-symmetric chiral terpyridine-...Comprehensive Summary Terpyridine ligands have been applied as a class of unique ligands due to their rich coordination chemistry in the catalysis.Herein,we developed a new class of C_(2)-symmetric chiral terpyridine-pyrroloimidazolone ligands(TPy-BPI).Their catalytic activity was evaluated in the asymmetric Friedel-Crafts alkylation of indoles with 2,3-dioxopyrrolidines.Excellent yields(up to 92%)and high enantioselectivities(up to 97%ee)are obtained for a wide range of substrates under mild conditions.展开更多
The atom-economical reaction of carbon dioxide(CO_(2))with epoxides possesses the potential to utilize captured CO_(2)for synthesizing useful chemicals.Among a wide range of metal complexes employed for this transform...The atom-economical reaction of carbon dioxide(CO_(2))with epoxides possesses the potential to utilize captured CO_(2)for synthesizing useful chemicals.Among a wide range of metal complexes employed for this transformation,iron(Fe)stands out because of its low cost,ready availability,and stability.In this work,a pyridine-based pincer PN^(3)-Fe(II)complex was synthesized and used as an efficient catalyst for the CO_(2)epoxide cycloaddition.More importantly,this complex enabled the direct capture of CO_(2)in the atmosphere and conversion into cyclic carbonates in excellent yields.展开更多
Readily prepared chiral bis(imidazoline)NCN pincer iridium(III)complexes have been developed as the new and highly stereoselective catalysts for the direct asymmetric addition of terminal alkynes to trifluoropyruvates...Readily prepared chiral bis(imidazoline)NCN pincer iridium(III)complexes have been developed as the new and highly stereoselective catalysts for the direct asymmetric addition of terminal alkynes to trifluoropyruvates.With a catalyst loading of 5 mol%,a variety of optically activeα-trifluoromethylated tertiary propargylic alcohols were thus produced in good yields with high enantioselectivity(27 examples,74%–96%ee).Both enantiomers of the catalysis products were obtained by using enantiomeric Ir(III)catalysts.In addition,gram scale synthesis of the product and its transformation to a potentially very useful 2H-1,2,3-triazole compound were accomplished.Control experiments suggested that the alkynylide Ir(III)intermediates were involved in the reactions.展开更多
A new type of dianionic Ir(Ⅲ) CCC pincer complexes(SNHC-Ir, 1a–1c) is successfully designed and synthesized by developing a one-step methodology, which involves an initial coordination of Ir(I) with the NHC and subs...A new type of dianionic Ir(Ⅲ) CCC pincer complexes(SNHC-Ir, 1a–1c) is successfully designed and synthesized by developing a one-step methodology, which involves an initial coordination of Ir(I) with the NHC and subsequent metallation of double sp2C–H bonds. This method is considerably useful over those reported by using strong coordination ligand or carbonic anion exchange,and would provide an alternative efficient template of organometallics synthesis. Experimental and density functional theory(DFT) calculation results indicate that the spirocyclic framework is a favourable factor for the facile formation and stabilization of these complexes. Primary investigation shows that chloride 1b can well catalyze homo and hetero addition of styrene derivatives and remote olefin isomerization, which represents the first catalytic application of the dianionic CCC pincer complexes.展开更多
Catalyst innovation lies at the heart of transition-metal-catalyzed reaction development.In this article,we have explored the C(sp2)–H alkenylation activity with novel spirocyclic N-heterocyclic carbene(NHC)-based cy...Catalyst innovation lies at the heart of transition-metal-catalyzed reaction development.In this article,we have explored the C(sp2)–H alkenylation activity with novel spirocyclic N-heterocyclic carbene(NHC)-based cyclometalated ruthenium pincer catalyst system,SNRu-X.After screening catalyst and condition,a high valent Ru(Ⅳ)dioxide(X=O_(2))species has demonstrated superior reactivity in the catalytic alkenylation of aromatic and olefinic C–H bonds with unactivated alkenyl bromides and triflates.This reaction has achieved the easy construction of a wide range of(hetero)aromatic alkenes and dienes,in good to excellent yields with exclusive selectivity.Preliminary mechanistic studies indicate that this reaction may proceed through a single electron transfer(SET)triggered oxidative addition,by doing so,providing valuable complementary to classical alkenylation reactions that are dependent on activated alkenyl precursors.展开更多
基金the financial support of the National Natural Science Foundation of China(No.21672133)the Opening Foundation of Key Laboratory of Applied Surface and Colloid Chemistry,Ministry of Education(No.GK202205011)the Fundamental Research Funds for the Central Universities(Nos.GK202307007 and GK202002003)。
文摘A cobalt pincer complex bearing both P and C-stereogenic centers has been designed and synthesized,allowing for the development of the first cobalt-catalyzed asymmetric hydrogenation of quinoxalines under relatively mild conditions.Valuable chiral 1,2,3,4-tetrahydroquinoxalines could be obtained with high yields and excellent enantioselectivities(35 examples,up to>99%ee).
基金Financial support from the State General Administration of the People’s Republic of China for Quality Supervision and Inspection and Quarantine(No.2016QK122)the Science and Technology Projects of Jiangxi Province(No.20181BBH80007)+1 种基金Shanghai Institute of Quality Inspection and Technical Researchthe Department of Chemistry,Fudan University。
文摘A convenient colorimetric approach for visual detection of melamine in raw milk was realized by using gold nanoparticles(AuNPs)stabilized by an unsymmetrical terpyridyl zinc complex with a thymine fragment at one terminal and a quaternary ammonium salt at the other.Even without pre-addition of melamine or relative additives,obvious color change from red to blue was observed by naked eye in the presence of trace amount of melamine,which was attributed to the alternation of aggregation state of AuNPs caused by the selective binding between the thymine fragment and melamine via triple hydrogenbonding interactions.Remarkably,the detection limit for melamine was as low as 2.4 ppb,providing a highly sensitive and efficient approach for the visual detection of melamine.
基金supported by the National Natural Science Foundation of China(Nos.21988101 and 22201013)Beijing Natural Science Foundation(No.2222008)supported by the High-performance Computing Platform of Peking University。
文摘A nonsymmetrical PNN pincer ligand[6-(^(t)Bu_(2)PNH)C_(5)H_(4)N-2-(3-Mes)C_(3)H_(2)N_(2)]and its corresponding cobalt-N_(2)complex were synthesized and characterized.By the stoichiometric reaction of the PNN ligand lithium salt with CoCl_(2),the complex 3,(PNN)CoCl,was obtained.Then,reduction of 3 with NaBHEt3under a dinitrogen atmosphere yielded complex 5,(PNN)Co(Ⅰ)(η^(1)-N_(2)).Single-crystal X-ray analysis,IR spectrum,and DFT calculations revealed that the dinitrogen in 5 was only weakly reduced by the cobalt center.The reactions of 5 with carbon monoxide and 2,6-dimethylphenyl isocyanide gave carbonyl and isocyanide complexes 6 and 7 with the release of N_(2),respectively.Furthermore,these cobalt complexes,especially complex 5,demonstrated the capacity to convert dinitrogen to N(TMS)_(3)with moderate efficiency.
基金supported by a grant from the National Nat-ural Science Foundation of China(No.21472176).
文摘The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is readily scaled up to 2 mmol scale without any loss in activity and enantioselectivity. Density functional theory(DFT)calculations have been performed to better understand the reaction mechanism and to explain the stereochemical outcome of the reactions.
基金the US National Science Foundation(grant CHE-1062840 for the REU site at TAMU and grant CHE-1300299 to O.V.O.)the Welch Foundation(grant A-1717 to O.V.O.)for support of this research.We are also grateful to Ms.Linda Redd for editorial assistance,to Allen Lunsford for assistance with cyclic voltammetry measurements,and to Prof.Andrei Vedernikov for insightful discussions.
文摘Platinum complexes of the diimino/carbazolyl NNN pincer ligand have been prepared and characterized.Cyclometallation of the mesityl substituent was observed to occur unexpectedly easily in(NNN)PtOTf,which also catalyzed cyclometallation in(NNN)PtMe.Introduction Pincer complexes have gained in popularity in part because they offer a robust and well-defined framework for study of elementary reactions at transition metal centers.1 Our group,among many others,has been particularly attracted to pincer ligands based on the diarylamido central unit with ortho-positioned side donors(Chart 1).
文摘Iron catalysis is attractive for organic synthesis because iron is inexpensive,abundant,and non-toxic.To control the activity and stability of an iron center,a large number of iron pincer complexes have been synthesized.Many such complexes exhibit excellent catalytic activity in a number of important organic reactions such as hydrogenation,hydrosilylation,dehydrogenation,and carbon-carbon bond forming reactions.In this review,recent examples of representative iron pincer catalysts are presented.
基金support from the Connecticut NASA Space Grant Alliance for this project(award number P-1168)JRM also thanks the National Science Foundation(CHE-1827854)for the acquisition of a 400 MHz NMR Spectrometer and Fairfield University for awarding JRM a Summer Research Stipend.RMK,EMA,and SEZ thank the Hardiman Scholars Program at Fairfield University for generous summer research support.
文摘This work reports the first example of mono-nuclear Cu pincers with SNS ligation acting as electrocatalyst precursors for the electrochemical conversion of carbon dioxide to CO and H_(2)in protic organic media.
基金the National Science Foundation(CHE-0952083)Alfred P.Sloan Foundation(research fellowship to H.G.)the University of Cincinnati Honors Program for supporting this research.
文摘Palladium POCOP-pincer hydride complexes[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdH(R=tBu,2a;R=^(i)Pr,2b;R=^(c)Pe,2c,^(c)Pe=cyclopentyl)have been synthesized from[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCl(1a-c)and LiAlH_(4) or LiBEt_(3)H.These hydride complexes react with phenylacetylene to afford H2,[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCuCPh(3a-c)and a small amount of styrene.When the R groups are isopropyl groups,a second palladium species is generated,and it has been identified as an alkenyl complex(E)-[2,6-(^(i)Pr_(2)PO)_(2)C_(6)H_(3)]PdCHvCHPh(4b).Mechanistic studies have shown that decomposition of these palladium pincer complexes and related palladium methyl complexes[2,6-(R_(2)PO)_(2)C_(6)H_(3)]PdCH_(3)(5a-c)occurs at room temperature in the presence of H_(2)(1 atm or lower),resulting in the leaching of palladium particles.These particles have been shown to catalyze the hydrogenation of phenylacetylene and diphenylacetylene to their alkene and alkane products.A mechanism for the formation of palladium particles has been proposed.The structures of 1a,1c,2a,2c,3a,4b and 5b have been studied by X-ray crystallography.
文摘This work describes the efficacy of[PNP]PdCl(1a),where[PNP]^(-)=bis(2-diphenylphosphinophenyl)amide,as a catalyst precursor for C_(sp)-C_(sp2) bond-forming cross-coupling reactions of terminal alkynes with aryl halides in the presence of copper bromide and aliphatic amines in ethereal solutions under mild conditions.This catalysis is compatible with acetylenes that are alkyl,alkenyl,(hetero)aryl,or silyl substituted and aryl iodides or bromides that are electronically activated,neutral,or deactivated.The low reaction constants of 0.82(6)and 0.97(7)obtained from Hammett plots of competitive reactions employing electronically distinct aryl iodides and terminal alkynes,respectively,are likely suggestive of irrelevance of the rate-determining step in these catalytic transformations to oxidative addition of aryl halides or generation of mono-substituted acetylides.In sharp contrast,reactions employing a phosphorus-bound isopropyl derived 1b gave rather unsatisfactory results,highlighting a profound phosphorus substituent effect on this aryl alkynylation catalysis.
基金supported by a National Science Centre Grant UMO-2018/30/E/ST5/00045.
文摘The hydroboration of alkenes catalyzed using an inexpensive and easily accessible Earth-abundant cobalt pincer complex based on a PN5P triazine backbone is reported.The presented protocol allows efficient anti-Markovnikov functionalization of alkenes bearing a wide range of functional groups(unsaturated amines,carbonates,ethers,vinylarenes,vinylsilanes,and natural products)under mild conditions with high yields.Moreover,the presented procedure exhibits unique selectivity distinguishing vinylsilyl groups from other alkenyl or alkyne groups,leading to an interesting class of bifunctional compounds that have potential application in the synthesis of advanced materials.Their application potential was demonstrated by several model transformations.
基金the Welch Foundation(grant A-1717 to O.V.O.)and the National Science Foundation(grant DMR-1654029 to L.F.)for support of this research.The。
文摘We report a series of redox-active bis(pincer)Pd(II)complexes in which the redox active units are based on either a diarylamido or a carbazolide framework.Compounds 1 and 2 contain two full diarylamido/bis(pincer)PNP units connected either via an Ar–O–Ar linker(1)or an Ar–Ar bond(2).Compound 3 is a fused bis(pincer)where the two PNP units share an aromatic ring.
基金support by the DFG(project code 419924354)is gratefully acknowledged.
文摘Herein we report the application of a Co(II)PNN^(H) pincer catalyst system(PNN^(H)=2-(5-(t-butyl)-1Hpyrazol-3-yl)-6-(dialkylphosphinomethyl)pyridine)for the highly E-selective transfer semihydrogenation of internal diaryl alkynes using methanol and ammonia borane as hydrogen donors.The catalyst system is highly active(short reaction times,low Co concentration)and operates at very mild conditions(low temperature and transfer hydrogenation conditions).Spectroscopic and computational studies suggest that catalysis occurs via the Co(II)oxidation state,most likely with a Co(II)hydride as the key intermediate.Computational analysis of the reaction mechanism further rationalises the selective formation of E-alkenes and the absence of overreduction to produce alkanes.
基金supported by the National Research Foundation of Korea(2022M3C1A3092056 to Y.L.and RS-2025-02634479 to S.L.)Seoul National University(Mid-Career Bridging Program to Y.L.and Ascending SNU Future Leader Fellowship to S.L.).
文摘Photoactive,octahedral transition metal complexes supported by rigid,multidentate ligand scaffolds have been successfully deployed for diverse photochemical processes.Challenges remain,however,in addressing deficiencies in reaction scalability,selectivity,and media penetration.In this regard,the development of new materials with intense red or near-infrared(NIR)absorption is of great interest.Herein,we report the synthesis,structure,and spectroscopic characterization of air-stable,dicationic transition metal complexes[M(CNC)_(2)]^(2+)(M=Cr,Mn,and Fe)supported by bis(carbene)-amide CNC pincer ligands.Results show intense NIR absorption(ε_(max)≈10000 M^(−1) cm^(-1))with the metal-dependent peak maxima spanning the first and second NIR regions.Importantly,the lowest energy main NIR absorption in each complex is assigned to the ligand-to-metal charge-transfer(LMCT)transition from the amide-based non-bonding orbital to the three-centered N–M–Nπ-antibonding orbital.Broadly,our studies provide a blueprint for the design of intense NIR-absorbing metal complexes based on a parallel N–M–Nπ-bonding motif with flanking strong field carbene donors.
基金financially supported by“Carbon to X Project”(2020M3H7A1098259&2020M3H7A1098271)through National Research Foundation(NRF)funded by the Ministry of Science&ICT and the Korea Institute of Science and Technology(KIST)supported by the Chung-Ang University Research Scholarship Grants in 2020.
文摘NNN pincer incorporated porous organic polymers(POPs)were prepared using a facile knitting method of pyridine based ligands via the Friedel–Crafts reaction.Ru-based molecular catalysts supported on the prepared POPs were implemented for catalytic CO_(2)hydrogenation into formate and methyl formate.In particular,a heterogeneous Ru/N-Me-3-bpp-POP catalyst exhibited the maximum catalytic conversion of CO_(2)into formate,with a turnover number(TON)of 1877,and into methyl formate with a TON of 2197.In addition,the stability of the Ru/N-Me-3-bpp-POP catalyst was demonstrated over five successive runs with a slight decrease in the catalytic efficiency,which may originate from Ru leaching.
基金the financial support from the NSFC(22061006)Key Laboratory of Applied Surface and Colloid Chemistry(Shaanxi Normal University)of Ministry of Education,Natural Science Basic Research Plan in Shaanxi Province of China(No.2024JC-YBMS-119)+1 种基金Key Research and Development Plan Project of Xianyang(L2023-ZDYF-QYCX-030)Guizhou Provincial Basic Research Program(GCC[2023]078,ZK[2023]043,ZK[2022]144).
文摘Comprehensive Summary Terpyridine ligands have been applied as a class of unique ligands due to their rich coordination chemistry in the catalysis.Herein,we developed a new class of C_(2)-symmetric chiral terpyridine-pyrroloimidazolone ligands(TPy-BPI).Their catalytic activity was evaluated in the asymmetric Friedel-Crafts alkylation of indoles with 2,3-dioxopyrrolidines.Excellent yields(up to 92%)and high enantioselectivities(up to 97%ee)are obtained for a wide range of substrates under mild conditions.
基金support was provided by King Abdullah University of Science and Technology(KAUST).
文摘The atom-economical reaction of carbon dioxide(CO_(2))with epoxides possesses the potential to utilize captured CO_(2)for synthesizing useful chemicals.Among a wide range of metal complexes employed for this transformation,iron(Fe)stands out because of its low cost,ready availability,and stability.In this work,a pyridine-based pincer PN^(3)-Fe(II)complex was synthesized and used as an efficient catalyst for the CO_(2)epoxide cycloaddition.More importantly,this complex enabled the direct capture of CO_(2)in the atmosphere and conversion into cyclic carbonates in excellent yields.
基金supported by grants from the National Natural Science Foundation of China(Nos.21472176 and U1904212)the Natural Science Foundation of Henan Province(No.222300420294)the China Postdoctoral Science Foundation(No.2020M672260).
文摘Readily prepared chiral bis(imidazoline)NCN pincer iridium(III)complexes have been developed as the new and highly stereoselective catalysts for the direct asymmetric addition of terminal alkynes to trifluoropyruvates.With a catalyst loading of 5 mol%,a variety of optically activeα-trifluoromethylated tertiary propargylic alcohols were thus produced in good yields with high enantioselectivity(27 examples,74%–96%ee).Both enantiomers of the catalysis products were obtained by using enantiomeric Ir(III)catalysts.In addition,gram scale synthesis of the product and its transformation to a potentially very useful 2H-1,2,3-triazole compound were accomplished.Control experiments suggested that the alkynylide Ir(III)intermediates were involved in the reactions.
基金This work was supported by the National Natural Science Foundation of China(21502080,21772076,21871117,21772071,21702136,91956203)the“111”Program of Ministry of Education of China,the Major Project(2018ZX09711001-005-002)of Ministry of Science and Technology of China+2 种基金the Science and Technology Commission of Shanghai Municipality(19IC1430100)This work was supported by the High-Performance Computing Center of Shanghai Jiao Tong UniversityAlso,we thank Prof.Qing-Wei Zhang from the University of Science and Technology of China for his helpful discussion.
文摘A new type of dianionic Ir(Ⅲ) CCC pincer complexes(SNHC-Ir, 1a–1c) is successfully designed and synthesized by developing a one-step methodology, which involves an initial coordination of Ir(I) with the NHC and subsequent metallation of double sp2C–H bonds. This method is considerably useful over those reported by using strong coordination ligand or carbonic anion exchange,and would provide an alternative efficient template of organometallics synthesis. Experimental and density functional theory(DFT) calculation results indicate that the spirocyclic framework is a favourable factor for the facile formation and stabilization of these complexes. Primary investigation shows that chloride 1b can well catalyze homo and hetero addition of styrene derivatives and remote olefin isomerization, which represents the first catalytic application of the dianionic CCC pincer complexes.
基金suported by the National Natural Science Foundation of China(2187,1117,91956203)the“111”Program of Minister of Education,Beijing National Laboratory for Molecular Sciences(BNLMS202109)the Science and Technology Commission of Shanghai Municipality(19JC1430100)。
文摘Catalyst innovation lies at the heart of transition-metal-catalyzed reaction development.In this article,we have explored the C(sp2)–H alkenylation activity with novel spirocyclic N-heterocyclic carbene(NHC)-based cyclometalated ruthenium pincer catalyst system,SNRu-X.After screening catalyst and condition,a high valent Ru(Ⅳ)dioxide(X=O_(2))species has demonstrated superior reactivity in the catalytic alkenylation of aromatic and olefinic C–H bonds with unactivated alkenyl bromides and triflates.This reaction has achieved the easy construction of a wide range of(hetero)aromatic alkenes and dienes,in good to excellent yields with exclusive selectivity.Preliminary mechanistic studies indicate that this reaction may proceed through a single electron transfer(SET)triggered oxidative addition,by doing so,providing valuable complementary to classical alkenylation reactions that are dependent on activated alkenyl precursors.
