氮掺杂有序介孔碳-Ni纳米复合材料的制备及电化学性能

以F127为模板剂,Ni Cl2为镍源,尿素为氮源,间苯二酚甲醛原位聚合树脂为碳源,分别采用均相法和两相法制备Ni-NOMC-1,Ni-N-OMC-2纳米复合材料。X射线衍射(XRD)、激光拉曼以及透射电子显微镜(TEM)等测试结果表明,复合材料具有有序介孔结构,Ni以金属微粒形式嵌于碳骨架中,提高了有序介孔碳的石墨化程度。X射线光电子能谱测试(XPS)表明尿素热解后以4种形式存在:sp3杂化与C结合的N原子,吡啶N原子,sp2杂化与C结合的N原子以及quaternary-N原子。Ni-N的共改性改变了碳载体的理化性质,有利于Pt纳米粒子的负载与分散。均相法制备的Ni-N-OMC-1复合材料微波负载Pt后,氧还原极限电流密度为5.32 m A·cm-2,氢氧化电化学活性面积高达138.53 m2·g-1,电化学催化活性优于商业20%Pt/C材料(4.49 m A·cm-2,96.98 m2·g-1)。     

Recent Progress towards Transition‐Metal‐Catalyzed Synthesis of Fluorenes

Fluorenes are a commonly encountered structural motif in materials science, pharmaceutical chemistry, and organic synthesis. Among various strategies towards the synthesis of this unique structure, transition metal‐catalyzed functionalization has emerged as one of the most efficient methods. This Minireview presents an overview of the recent advances in this emerging area by highlighting the reactions’ specificity and applicability and, where possible, provides a mechanistic rationale.     

Synthesis,Characterisation and Reactivity of Copper(I) Amide Complexes and Studies on Their Role in the Modified Ullmann Amination Reaction

A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide ( 1 ), copper(I) 2,2,6,6‐tetramethylpiperidide ( 2 ), copper(I) pyrrolidide ( 3 ), copper(I) piperidide ( 4 ), and copper(I) benzylamide ( 5 ). Their solid‐state structures and structures in [D₆]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1 , 2 and 4 are shown to exist as tetramers in the solid state by X‐ray crystallography. In [D₆]benzene solution, complexes 1 , 2 and 5 were found by using ¹H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 M concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one‐dimensional ¹H and ¹H DOSY NMR spectroscopy. Complexes 3 – 5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10‐phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol.     

Olefin Polymerization Catalyzed by Double‐Decker Dipalladium Complexes: Low Branched Poly(α‐Olefin)s by Selective Insertion of the Monomer Molecule

Dipalladium complexes of a cyclic bis(diimine) ligand with a double‐decker structure catalyze polymerization of ethylene and α‐olefins and copolymerization of ethylene with 1‐hexene. The polymerization of 1‐hexene yields a polymer that is mainly composed of the hexamethylene unit formed by 2,1‐insertion of the monomer into the palladium–carbon bond, followed by chain‐walking (6,1‐insertion). The polymerization of 4‐methyl‐1‐pentene proceeds by 2,1‐insertion with a selectivity of 92–97 %, and affords the polymer with methyl and 2‐methylhexyl branches. 2,1‐Insertion occurs selectively in all of the polymerization reactions of α‐olefins catalyzed by the dipalladium complexes. Ethylene polymerization with the catalyst at 100 °C lasts over 24 h, whereas the monopalladium–diimine catalyst loses its activity within 8 h at 60 °C. Polyethylene obtained by the dipalladium catalyst is less‐branched and has a higher molecular weight compared to that of the monopalladium catalyst under the same conditions. Copolymerization of ethylene with 1‐hexene affords solid products with melting points and molecular weights that vary depending on the polymerization time, suggesting formation of a block and/or gradient copolymer.     

Synthesis of 8‐Aminoquinolines by Using Carbamate Reagents: Facile Installation and Deprotection of Practical Amidating Groups

Described herein is the development of practical routes to 8‐aminoquinolines by using readily installable and easily deprotectable amidating reagents. Two scalable procedures were optimized under Rh^III‐catalyzed conditions: i) the use of pre‐generated chlorocarbamates and ii) a two‐step one‐pot process that directly employs carbamates. Both approaches are highly convenient for the gram‐scale synthesis of 8‐aminoquinolines under mild conditions. Facile deprotection of the synthetically versatile amidating groups was achieved under the Pd‐catalyzed transfer hydrogenation conditions with simultaneous deoxygenation of quinoline N‐oxides, thus yielding 8‐aminoquinolines in excellent overall efficiency.     

Terminal Phosphanido Rhodium Complexes Mediating Catalytic PP and PC Bond Formation

Complexes with terminal phosphanido (M? PR₂) functionalities are believed to be crucial intermediates in new catalytic processes involving the formation of P? P and P? C bonds. We showcase here the isolation and characterization of mononuclear phosphanide rhodium complexes ([RhTp(H)(PR₂)L]) that result from the oxidative addition of secondary phosphanes, a reaction that was also explored computationally. These compounds are active catalysts for the dehydrocoupling of PHPh₂ to Ph₂P? PPh₂. The hydrophosphination of dimethyl maleate and the unactivated olefin ethylene is also reported. Reliable evidence for the prominent role of mononuclear phosphanido rhodium species in these reactions is also provided.     

Ortho‐Quinone Methides as Reactive Intermediates in Asymmetric Brønsted Acid Catalyzed Cycloadditions with Unactivated Alkenes by Exclusive Activation of the Electrophile

An efficient method for the highly enantioselective synthesis of chiral chromanes bearing multiple stereogenic centers was developed. A chiral BINOL‐based N‐triflylphosphoramide proved to be an effective catalyst for the in situ generation of ortho‐quinone methides (o‐QMs) and their subsequent cycloaddition reaction with unactivated alkenes provided chromanes with excellent diastereo‐ and enantioselectivity.     

Tuning the Reactivity of Isocyano Group: Synthesis of Imidazoles and Imidazoliums from Propargylamines and Isonitriles in the Presence of Multiple Catalysts

The reaction of propargyl amines with tert‐butylisonitrile in the presence of a catalytic amount of both Yb(OTf)₃ and AgOTf afforded imidazoles, whereas the same reaction with primary and secondary alkylisonitriles, as well as arylisonitriles, in the presence of three metal salts [Yb(OTf)₃/AgOTf/KOTf] resulted in the 1,3,4,5‐tetrasubstituted imidazoliums in excellent yields. Both chiral amines and chiral isonitriles can be used to provide corresponding chiral heterocycles without racemization. In this multiple catalytic system, Yb(OTf)₃ catalyzed the insertion of isonitriles to the N? H bond of amines, AgOTf catalyzed the 5‐exo‐dig cyclization of the resulting amidine nitrogen to the tethered triple bond, and KOTf promoted the salt metathesis, thus providing at the same time the counterion to the imidazolium. Against common knowledge, the isocyano group acted in these reactions as a polarized triple bond instead of conventional carbene‐like function.     

A General and Mild Catalytic α‐Alkylation of Unactivated Esters Using Alcohols

Catalytic α‐alkylation of esters with primary alcohols is a desirable process because it uses low‐toxicity agents and generates water as the by‐product. Reported herein is a NCP pincer/Ir catalyst which is highly efficient for α‐alkylation of a broad scope of unactivated esters under mild reaction conditions. For the first time, alcohols alkylate unactivated α‐substituted acyclic esters, lactones, and even methyl and ethyl acetates. This method can be applied to the synthesis of carboxylic acid derivatives with diverse structures and functional groups, some of which would be impossible to access by conventional enolate alkylations with alkyl halides.     

Gold‐Catalyzed Intermolecular Anti‐Markovnikov Hydroamination of Alkylidenecyclopropanes

The cationic gold phosphine complex [{PCy₂(o‐biphenyl)}Au(NCMe)]⁺SbF₆^? (Cy=cyclohexyl) catalyzes the intermolecular, anti‐Markovnikov hydroamination reaction of monosubstituted and cis‐ and trans‐disubstituted alkylidenecyclopropanes (ACPs) with imidazolidin‐2‐ones and other nucleophiles. This reaction forms 1‐cyclopropyl alkylamine derivatives in high yield and with high regio‐ and diastereoselectivity. NMR spectroscopic analysis of gold π‐ACP complexes and control experiments point to the sp hybridization of the ACP internal alkene carbon atom as controlling the regiochemistry of the ACP hydroamination reaction.