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
Extracting hydrogen from methanol is a safe and cost-efficient strategy for fuel supply. This process was realized recently at a mild condition with excellent efficiency by ruthenium pincer catalysts. Despite the expe...Extracting hydrogen from methanol is a safe and cost-efficient strategy for fuel supply. This process was realized recently at a mild condition with excellent efficiency by ruthenium pincer catalysts. Despite the experimental success, the associated mechanism remains under debate. With the aid of density functional theory(DFT) calculations, an updated and self-consistent mechanism which involves Me OH-catalysed dehydrogenation of ruthenium hydride intermediate and pre-protonation of the pincer ligand was present herein. This mechanism is kinetically favoured over the previously-proposed water- or formic- acid-participated ones and more consistent with the optimal experimental condition where strong base and neat methanol solvent are used.展开更多
Olefins find widespread applications in the synthesis of polyolefins and fine chemicals. With an increasing demand for olefins, the technologies for alkane dehydrogenation have drawn much attention. Several types of h...Olefins find widespread applications in the synthesis of polyolefins and fine chemicals. With an increasing demand for olefins, the technologies for alkane dehydrogenation have drawn much attention. Several types of heterogeneous catalysts have found applications in industry for the dehydrogenation of light alkanes, mainly ethane, propane, and butane. In the past three decades, a number of transition-metal complexes,particularly pincer-ligated iridium complexes, have been developed as the homogeneous catalysts for alkane dehydrogenations. The homogeneous catalyst systems operate under much milder conditions compared with the heterogeneous systems, and some systems exhibit good activity and high regioselectivity in dehydrogenation of alkanes longer than butane.展开更多
Pincer complexes are widely used in organometallic and coordination chemistry.The role of antimony as a central donor atom in pincer ligands has been extensively explored in recent years.Although phenylenediamine deri...Pincer complexes are widely used in organometallic and coordination chemistry.The role of antimony as a central donor atom in pincer ligands has been extensively explored in recent years.Although phenylenediamine derived PXP(X=B,Al,C,Si,Ge,Sn,N) type ligands exhibit diverse reactivity,analogues species based on antimony have been reported less frequently.Herein,we report a new PSbP complex and evaluate its reactivity.These species will broaden the family of phenylenediamine derived pincer complexes.展开更多
Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus...Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus(Ⅲ)species was reported.A series of structurally robust phosphorus(Ⅴ)compounds were formed via the formal oxidative addition reactions of C-X bonds to the phosphorus(Ⅲ)center.Density functional theory calculations show that the nucleophilic addition process is more favorable than the direct oxidative addition mechanism.Isomerization of bent structures of phosphorus(Ⅲ)compound to poorly nucleophilic compounds to undergo further C-X bond activation can be rationalized by frontier molecule orbital analysis.This study not only provides a deep understanding of the reactivity of phosphorus(Ⅲ)species but also demonstrates a potential of main group elements for the small-molecule activation.展开更多
A class of chiral 1,3-bis(diarylphosphinoethyl)benzenes, which are key intermediates for the synthesis of PCP-type chiral pincer ligands, were prepared in high diastereomeric ratios and excellent ee values via double ...A class of chiral 1,3-bis(diarylphosphinoethyl)benzenes, which are key intermediates for the synthesis of PCP-type chiral pincer ligands, were prepared in high diastereomeric ratios and excellent ee values via double asymmetric hydrogenation of the corresponding bis(diarylvinylphosphine oxide) substrates using a SpinPhox/Ir(I) complex as the catalyst. The hydrogenation product 5a was readily transformed into the corresponding borane-protected chiral PCP-type pincer ligand 7a with high enantiomeric excess, exemplifying a viable synthetic route to optically active chiral PCP pincer ligands.展开更多
Catalytic dehydrogenation,with its exceptional atom economy and chemoselectivity,offers a highly desirable yet challenging approach for converting multiple environmentally friendly alcohols into crucial molecules.Furt...Catalytic dehydrogenation,with its exceptional atom economy and chemoselectivity,offers a highly desirable yet challenging approach for converting multiple environmentally friendly alcohols into crucial molecules.Furthermore,the utilization of catalysts based on abundant elements found on Earth for alcohol dehydrogenation to produce acryl ketone holds significant promise as a versatile strategy in synthesizing key building blocks for numerous pharmaceutical applications.The present study describes a practical Co-catalyzed cascade dehydrogenative Claisen condensation of secondary alcohols with esters,facilitating the synthesis of a wide range of 3-hydroxy-prop-2-en-1-ones.We introduce a catalytic system based on novel and scalable indazole NNP-ligands coordinated to cobalt for efficient dehydrogenations of secondary alcohols,and propose a plausible reaction mechanism supported by control experiments and labeling studies.Notably,it allows for the streamlined synthesis of multiple pharmaceuticals in one-pot.展开更多
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 the National Basic Research Program (2012CB215306)the National Natural Science Foundation of China (21325208, 21361140372, 21572212)+2 种基金Chinese Academy of Sciences (KFJ-EW-STS-051)Fundamental Research Funds for the Central Universities (WK2060190025)Scientific research funds of Anhui University (J10117700074)
文摘Extracting hydrogen from methanol is a safe and cost-efficient strategy for fuel supply. This process was realized recently at a mild condition with excellent efficiency by ruthenium pincer catalysts. Despite the experimental success, the associated mechanism remains under debate. With the aid of density functional theory(DFT) calculations, an updated and self-consistent mechanism which involves Me OH-catalysed dehydrogenation of ruthenium hydride intermediate and pre-protonation of the pincer ligand was present herein. This mechanism is kinetically favoured over the previously-proposed water- or formic- acid-participated ones and more consistent with the optimal experimental condition where strong base and neat methanol solvent are used.
基金supported by the National Basic Research Program of China(2015CB856600)the National Natural Science Foundation of China(21422209,21432011,21421091)
文摘Olefins find widespread applications in the synthesis of polyolefins and fine chemicals. With an increasing demand for olefins, the technologies for alkane dehydrogenation have drawn much attention. Several types of heterogeneous catalysts have found applications in industry for the dehydrogenation of light alkanes, mainly ethane, propane, and butane. In the past three decades, a number of transition-metal complexes,particularly pincer-ligated iridium complexes, have been developed as the homogeneous catalysts for alkane dehydrogenations. The homogeneous catalyst systems operate under much milder conditions compared with the heterogeneous systems, and some systems exhibit good activity and high regioselectivity in dehydrogenation of alkanes longer than butane.
基金supported by the National Natural Science Foundation of China (Nos.21772088 and 91961116)the Fundamental Research Funds for the Central Universities (No.14380216)+2 种基金the Young Elite Scientist Sponsorship Program of China Association of Science and Technologythe Program of Jiangsu SpeciallyAppointed ProfessorShuangchuang Talent Plan of Jiangsu Province。
文摘Pincer complexes are widely used in organometallic and coordination chemistry.The role of antimony as a central donor atom in pincer ligands has been extensively explored in recent years.Although phenylenediamine derived PXP(X=B,Al,C,Si,Ge,Sn,N) type ligands exhibit diverse reactivity,analogues species based on antimony have been reported less frequently.Herein,we report a new PSbP complex and evaluate its reactivity.These species will broaden the family of phenylenediamine derived pincer complexes.
基金supported by the National Natural Science Foundation of China(Nos.21772088 and 21573179)the Natural Science Foundation of Jiangsu Province(No.BK20170635)the Young Elite Scientist Sponsorship Program of China Association of Science and Technology,the program of Jiangsu SpeciallyAppointed Professor and Shuangchuang Talent Plan of Jiangsu Province。
文摘Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus(Ⅲ)species was reported.A series of structurally robust phosphorus(Ⅴ)compounds were formed via the formal oxidative addition reactions of C-X bonds to the phosphorus(Ⅲ)center.Density functional theory calculations show that the nucleophilic addition process is more favorable than the direct oxidative addition mechanism.Isomerization of bent structures of phosphorus(Ⅲ)compound to poorly nucleophilic compounds to undergo further C-X bond activation can be rationalized by frontier molecule orbital analysis.This study not only provides a deep understanding of the reactivity of phosphorus(Ⅲ)species but also demonstrates a potential of main group elements for the small-molecule activation.
基金supported by the Basic Research Development Program of China(2010CB833300)the National Natural Science Foundation of China(21121062,21232009)+1 种基金the Chinese Academy of Sciencesthe Science and Technology Commission of Shanghai Municipality
文摘A class of chiral 1,3-bis(diarylphosphinoethyl)benzenes, which are key intermediates for the synthesis of PCP-type chiral pincer ligands, were prepared in high diastereomeric ratios and excellent ee values via double asymmetric hydrogenation of the corresponding bis(diarylvinylphosphine oxide) substrates using a SpinPhox/Ir(I) complex as the catalyst. The hydrogenation product 5a was readily transformed into the corresponding borane-protected chiral PCP-type pincer ligand 7a with high enantiomeric excess, exemplifying a viable synthetic route to optically active chiral PCP pincer ligands.
基金supported by the National Natural Science Foundation of China(22002067,22202228)the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(20220052)+1 种基金the Science and Technology Project of Shanxi Province(202103021223457,202303021221256)Research Project Supported by Shanxi Scholarship Council of China.
文摘Catalytic dehydrogenation,with its exceptional atom economy and chemoselectivity,offers a highly desirable yet challenging approach for converting multiple environmentally friendly alcohols into crucial molecules.Furthermore,the utilization of catalysts based on abundant elements found on Earth for alcohol dehydrogenation to produce acryl ketone holds significant promise as a versatile strategy in synthesizing key building blocks for numerous pharmaceutical applications.The present study describes a practical Co-catalyzed cascade dehydrogenative Claisen condensation of secondary alcohols with esters,facilitating the synthesis of a wide range of 3-hydroxy-prop-2-en-1-ones.We introduce a catalytic system based on novel and scalable indazole NNP-ligands coordinated to cobalt for efficient dehydrogenations of secondary alcohols,and propose a plausible reaction mechanism supported by control experiments and labeling studies.Notably,it allows for the streamlined synthesis of multiple pharmaceuticals in one-pot.
