Group IB organometallic chemistry: XXIX. Synthetic and structural aspects of polynuclear arylcopperlithium compounds Ar4Cu2Li2 (“arylcuprates”) and interaggregate exchange phenomena in Ar4Cu4/Ar4Li4/Ar4Cu2Li2 systems

The thermally stable arylmetal-IB-lithium compounds (2-Me₂NCHZC₆H₄)₄M₂Li₂ (M = Cu, Ag or Au; Z = H or Me) and (2-Me₂NC₆H₄)₄M₂Li₂ have been prepared by a $\text{2}\text{1}$ molar reaction of the aryllithium compounds with the corresponding metal-IB halide (Cu or Ag) or metal-lB halide phosphine complex (BrAuPPh₃). These tetranuclear complexes were also made by an interaggregate exchange reaction of the pure arylmetal-IB clusters with the aryllithium compound.The structure of these compounds in solution consists of aryl groups bridging one metal-lB and one lithium atom of a trans M₂Li₂ core. The four built-in ligands coordinate to lithium resulting in two-coordination at M and four-coordination at Li. These conclusions were based on ¹H and ¹³C NMR spectroscopic data (J(AgC(1)), J(LiC(1)) of solutions of these tetranuclear compounds as well as on the ¹⁹⁷Au Mössbauer data of solid (2-Me₂NC₆H₄)₄Au₂Li₂ (IS 5.65 mm/s and QS 12.01 mm/s).The interaggregate exchange between the tetranuclear species is discussed in terms of an associative mechanism involving formation of an octanuclear intermediate in which the aryl groups can migrate via (3c-2e)edge-(2c-2e)corner(3c-2e)edge movements without M₂Ar bond cleavage.Some aspects of the organic reactions in which organocuprates are involved as intermediates are discussed in terms of the novel structural information.     

Three Dimensionally Ordered Mesoporous Carbon as a Stable,High‐Performance Li–O2 Battery Cathode

Enabled by the reversible conversion between Li₂O₂ and O₂, Li–O₂ batteries promise theoretical gravimetric capacities significantly greater than Li‐ion batteries. The poor cycling performance, however, has greatly hindered the development of this technology. At the heart of the problem is the reactivity exhibited by the carbon cathode support under cell operation conditions. One strategy is to conceal the carbon surface from reactive intermediates. Herein, we show that long cyclability can be achieved on three dimensionally ordered mesoporous (3DOm) carbon by growing a thin layer of FeO_x using atomic layer deposition (ALD). 3DOm carbon distinguishes itself from other carbon materials with well‐defined pore structures, providing a unique material to gain insight into processes key to the operations of Li–O₂ batteries. When decorated with Pd nanoparticle catalysts, the new cathode exhibits a capacity greater than 6000 mAh g_carbon^?1 and cyclability of more than 68 cycles.     

Three Dimensionally Ordered Mesoporous Carbon as a Stable,High‐Performance Li–O2 Battery Cathode

Enabled by the reversible conversion between Li₂O₂ and O₂, Li–O₂ batteries promise theoretical gravimetric capacities significantly greater than Li‐ion batteries. The poor cycling performance, however, has greatly hindered the development of this technology. At the heart of the problem is the reactivity exhibited by the carbon cathode support under cell operation conditions. One strategy is to conceal the carbon surface from reactive intermediates. Herein, we show that long cyclability can be achieved on three dimensionally ordered mesoporous (3DOm) carbon by growing a thin layer of FeO_x using atomic layer deposition (ALD). 3DOm carbon distinguishes itself from other carbon materials with well‐defined pore structures, providing a unique material to gain insight into processes key to the operations of Li–O₂ batteries. When decorated with Pd nanoparticle catalysts, the new cathode exhibits a capacity greater than 6000 mAh g_carbon⁻¹ and cyclability of more than 68 cycles.     

Synthesis and reactivity of acyclic and macrocyclic uracils bridged with five-membered heterocycles

Replacement of terminal atoms of Br in 1,3-bis(bromopentyl)-5(6)-substituted uracils with 2-mercapto-5-methyl-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercaptoimidazole, and 2-mercaptobenzimidazoles resulted in a series of acyclic compounds and isomeric heterocyclophanes. Structures of macrocyclic regioisomers were unambiguously determined by NMR data. One of the regioisomers exhibits a hypochromic effect with respect to model compounds. The acyclic uracils obtained bridged with five-membered heterocycles are alkylated with methyliodide and methyl tosylate, and oxidated with m-CPBA, H₂O₂, and I₂.     

Anchoring an Artificial Solid–Electrolyte Interphase Layer on a 3D Current Collector for High‐Performance Lithium Anodes

The application of Li anodes is hindered by dendrite growth and side reactions between Li and electrolyte, despite its high capacity and low potential. A simple approach for this challenge is now demonstrated. In our strategy, the garnet‐type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO)‐based artificial solid–electrolyte interphase (SEI) is anchored on Cu foam by sintering the Cu foam coated with LLZTO particles. The heat treatment leads to the interdiffusion of Cu and Ta₂O₅ at the Cu/LLZTO interface, through which LLZTO layer is fixed on Cu foam. 3D structure lowers the current density, and meanwhile the SEI reduces the contact of Li and electrolyte. Furthermore, the anchoring construction can endure Li‐deposition‐induced volume change. Therefore, LLZTO‐modified Cu foam shows much improved Li plating/stripping performance, including long lifespan (2400 h), high rate (maximum current density of 20 mA cm^?2), high areal capacity (8 mA h cm^?2 for 100 cycles), and high efficiency (over 98 %).     

[Ph2P(NSiMe3)]2CLi2: A Dilithium Dianionic Methanide Salt with an Unusual Li4C2 Cluster Structure

Four lithium atoms in a square-planar arrangement are capped by two carbon atoms and encapsulated by NSiMe₃ chelation in the dilithium methanide salt 1 . This air- and moisture-sensitive complex is formed by the reaction of CH₂(Ph₂P=NSiMe₃)₂ with alkyl- or aryllithium reagents.     

Determination of triacylglycerol regioisomers using electrospray ionization-quadrupole ion trap mass spectrometry with a kinetic method

The kinetic method was applied to differentiate and quantify mixtures of regioisomeric triacylglycerols (TAGs) by generating and mass selecting alkali ion bound metal dimeric clusters with a TAG chosen as reference (ref) and examining their competitive dissociations in a quadrupole ion trap mass spectrometer. This methodology readily distinguished pairs of regioisomers (AAB/ABA) such as LLO/LOL, OOP/OPO and SSP/SPS and consequently distinguished sn-1/sn-3, sn-2 substituents on the glycerol backbone. The dimeric complex ions [ref, Li, TAG_{(AAB and/or ABA)}]⁺ generated by electrospray ionization mass spectrometry were subjected to collision induced dissociation causing competitive loss of either the neutral TAG reference (ref) leading to [Li(AAB and/or ABA)]⁺ or the neutral TAG molecule (TAG_{(AAB and/or ABA)}) leading to [ref, Li]⁺. The ratio of the two competitive dissociation rates, defined by the product ion branching ratio (R_iso), was related via the kinetic method to the regioisomeric composition of the investigated TAG mixture. In this work, a linear correlation was established between composition of the mixture of each TAG regioisomer and the logarithm of the branching ratio for competitive fragmentation. Depending on the availability of at least one TAG regioisomer as standard, the kinetic method and the standard additions method led to the quantitative analysis of natural TAG mixtures.     

Graphene-Enabled Electric-Field Regulation and Ionic Redistribution Around Lithiophilic Aurum Nanoparticles Toward a Dendrite-Free and 2000-Cycle-Life Lithium Metal Battery

Lithium metal batteries (LMBs) have attracted extensive attention owing to their high energy density. However, the uncontrolled volume changes and serious dendrite growth of the Li metal anode have hindered their commercialization. Herein, a three-dimensional Cu foam decorated with Au nanoparticles and conformal graphene layer was designed to tune the Li plating/stripping behaviors. The 3D−Cu conductive host anchored by lithiophilic Au nanoparticles can effectively alleviate the volume expansion caused by the continuous plating/stripping of Li and reduce the nucleation energy barrier. Notably, the conductive graphene not only facilitates the transfer of electrons, but also acts as an ionic rectifier, thereby avoiding the aggregation of local current density and Li⁺ ions around Au nanoparticles and enabling the uniform Li⁺ flux. As a result, the G−Au@3D−Cu/Li anode ensures the non-dendritic and homogeneous Li⁺ plating/stripping. Electrochemical results show that the symmetric G−Au@3D−Cu/Li cell delivers a low voltage hysteresis of 110 mV after 1000 h at 1 mA cm⁻². Matched with a layered LiNi_0.6Co_0.2Mn_0.2O₂ cathode, the NCM622||G−Au@3D−Cu/Li full cell exhibits a long cycle life of 2000 cycles and an ultra-low capacity decay rate (0.01 % per cycle).     

Intrinsic Stress-strain in Barium Titanate Piezocatalysts Enabling Lithium−Oxygen Batteries with Low Overpotential and Long Life

Rechargeable lithium−oxygen (Li−O₂) batteries with high theoretical energy density are considered as promising candidates for portable electronic devices and electric vehicles, whereas their commercial application is hindered due to poor cyclic stability caused by the sluggish kinetics and cathode passivation. Herein, the intrinsic stress originated from the growth and decomposition of the discharge product (lithium peroxide, Li₂O₂) is employed as a microscopic pressure resource to induce the built-in electric field, further improving the reaction kinetics and interfacial Lithium ion (Li⁺) transport during cycling. Piezopotential caused by the intrinsic stress-strain of solid Li₂O₂ is capable of providing the driving force for the separation and transport of carriers, enhancing the Li⁺ transfer, and thus improving the redox reaction kinetics of Li−O₂ batteries. Combined with a variety of in situ characterizations, the catalytic mechanism of barium titanate (BTO), a typical piezoelectric material, was systematically investigated, and the effect of stress-strain transformation on the electrochemical reaction kinetics and Li⁺ interface transport for the Li−O₂ batteries is clearly established. The findings provide deep insight into the surface coupling strategy between intrinsic stress and electric fields to regulate the electrochemical reaction kinetics behavior and enhance the interfacial Li⁺ transport for battery system.     

The formation of lithium diarylargentates from arylsilver compounds and the corresponding aryllithium compounds

Diarylsilverlithium compounds of the type Ar₂AgLi are formed by treating arylsilver compounds with the corresponding aryllithium compounds. Cryoscopy in benzene shows that the Ar₂AgLi compounds are associated into dimers. NMR spectroscopic data indicate that only one type of aryl group is present in these dimers, and that each aryl group is bridging between one silver and one lithium atom.     

[2 + 3]‐Cycloadditions of Phosphonodithioformate S‐Methanides with CS,NN,and CC Dipolarophiles

The reaction of the methyl (dialkoxyphosphinyl)‐dithioformates (= methyl dialkoxyphosphinecarbodithioate 1‐oxides) 10 with CH₂N₂ at − 65° in THF yielded cycloadducts which eliminated N₂ between − 40 and − 35° to give the corresponding phosphonodithioformate S‐methanides ( =methylenesulfonium (dialkoxyoxidophosphino)(methylthio)methylides) 11 (Scheme 3). These reactive 1,3‐dipoles were intercepted by aromatic thioketones to yield 1,3‐dithiolanes. Whereas the reaction with thiobenzophenone ( 12b ) led to the sterically more congested isomers 15 regioselectively, a mixture of both regioisomers was obtained with 9H‐fluorene‐9‐thione ( 12a ). Trapping of 11 with phosphono‐ and sulfonodithioformates led exclusively to the sterically less hindered 1,3‐dithiolanes 16 and 18 , respectively (Scheme 4). In addition, reactive CC dipolarophiles such as ethenetetracarbonitrile, maleic anhydride, and N‐phenylmaleimide as well as the NN dipolarophile dimethyl diazenedicarboxylate were shown to be efficient interceptors of 11 (Scheme 5).     

Synthetic studies on nogalamycin congeners [1]1 chiral synthesis of the def-ring system of nogalamycin

From the retrosynthetic perspective on nogalamycin congeners, the potent antitumor antibiotics of the anthra-cycline family, the regioselective Diels-Alder reaction employing the naphthoquinone (4), the CDEF-ring system of nogalamycin congeners, as a dienophile was anticipated to constitute the key step of one of the most convenient and flexible synthetic routes to their 11-deoxyanthracyclinone frameworks (3). As a model study to explore an efficient and reliable synthetic scheme to produce the characteristic bicyclic acetal structure of 4 in an optically active form, the preparation of the DEF-ring system (6) was first examined prior to the chiral synthesis of 4. The chiral synthesis of 6 accomplished starting from readily available (-)-D-arabinose (11), involves the following novel aspects: (1) synthesis of the suitably functionalized (-)-methylketone (18) from 11 through (-)-b-D-gentosaminide (14) which carries the stereochemistries at the C_2' -, C_3'-, and C_4'-positions, (2) stereoselective construction of the C5'-asymmetric center by chelation-controlled addition of the aryllithium [9 (M=Li)] to 18, (3) formation of the bicyclic acetal by treating the hydroquinone (28) with trimethylsilyl bromide.     

Substitution nucléophile aromatique cine d'un groupe méthoxy en série arènetricarbonylchrome

Treatment of veratroletricarbonylchromium (1a) with n-BuLi and ClSi(CHMe₂)₃ yields 3-triisopropylsilyl (2b), 3,6-bis(triisopropylsilyl)veratroletricarbonylchromium (3b) and an unexpected dinuclear complex, the formation of which is interpreted as a cine-nucleophilic aromatic substitution of a methoxy group by an aryllithium tricarbonylchromium complex.     

Reaction of 2-trifluoroacetyl-1,8-Bis(dimethylamino)naphthalene with strong organic bases: Deprotonation of 1-NMe2 group resulting in the formation of Benzo[g]indole derivatives versus nucleophilic addition to CO group

A novel approach to pyrrole ring closure in 2-trifluoroacetyl- and 2-ethoxycarbonyl-1,8-bis(dimethylamino)naphthalenes via treatment with 2-lithium-1,8-bis(dimethylamino)naphthalene producing the corresponding benzo[g]indole derivatives, was examined with different alkyl- and aryllithium compounds as well as with LDA. It was found that the highest yields of benzo[g]indoles (up to 70%) are obtained with aryllithium reagents when they contain NMe₂ group in ortho-position to the carbanionic centre. In all other cases the formation of acyclic alcohol arising from ordinary intermolecular addition of the carbanion to the CO group strongly prevails. The dramatic facilitation of deprotonation of the N-Me group in substrate followed by pyrrolic cyclization in the case of 2-lithium-N,N-dimethylanilines was explained through a specific structure of the reaction transition state.     

Synthese de derives mono- ou disilicies au niveau d'un carbone fonctionnel

Aliphatic saturated amides treated with Me₃SiCl/Li/THF were found to react in two ways. Either alkoxysilanes, mono- or di-silylated at the functional carbon, or C-silylated amines were obtained dependent of the original amide structure and the experimental conditions. (Me₃Si)₂CHN(SiMe₃)₂ exhibited Physicochemical properties that are particular for hindered rotation about the CN bond. A general mechanism is proposed to explain these results.     

Structural Analysis of Novel [60]Fullerene Bisadduct Regioisomers by DFT Calculation

The structural analysis of the first [60]fullerenyl 1,38-bisadduct having the almost perpendicular angle between two addends was performed based on the simulation of ¹³C-NMR spectral line patterns using the DFT calculation at the B3LYP/6-31G? level of the theory. Among seven closely related model regioisomers of C₆₀(CH₃)₂ applied in the calculation, we confirmed that the 1,38-bisadduct and 1,4-bisadduct, being the most plausible regioisomers in a structure showing an approximate consistency of spectral line profiles, match with that of the experimentally obtained spectrum.     

Preparation of solvated and/or unsolvated simple and mixed diarylmagnesiums

Arylation of arylmagnesium halides or magnesium halide etherates by aryllithium provides a convenient method of preparing Ar₂Mg(Et₂O)₂ or Ar₂Mg(THF)₂. The ether complexes can be completely desolvated but the THF complexes cannot. Mixed diarylmagnesium tetrahydrofuranates, Ar¹Ar²Mg(THF)₂, although coordinationally saturated, have ¹H and ¹³C NMR spectra which suggest that they are fluxional.     

Hybrids of MnO<Subscript>2</Subscript> nanoparticles anchored on graphene sheets as efficient sulfur hosts for high-performance lithium sulfur batteries

Lithium–sulfur (Li–S) battery is considered as a promising option for electrochemical energy storage applications because of its low-cost and high theoretical capacity. However, the practical application of Li–S battery is still hindered due to the poor electrical conductivity of S cathode and the high dissolution/shuttling of polysulfides in electrolyte. Herein, we report a novel physical and chemical entrapment strategy to address these two problems by designing a sulfur–MnO₂@graphene (S–MnO₂@GN) ternary hybrid material structure. The MnO₂ particles with size of ~ 10 nm are anchored tightly on the wrinkled and twisted GN sheets to form a highly efficient sulfur host. Benefiting from the synergistic effects of GN and MnO₂ in both improving the electronic conductivity and hindering polysulfides by physical and chemical adsorptions, this unique S–MnO₂@GN composite exhibits excellent electrochemical performances. Reversible specific capacities of 1416, 1114, and 421 mA h g^?1 are achieved at rates of 0.1, 0.2, and 3.2 C, respectively. After a 100 cycle stability test, S–MnO₂@GN composite cathode could still maintain a reversible capacity of 825 mA h g^?1.     

Influencing Factors on Li-ion Conductivity and Interfacial Stability of Solid Polymer Electrolytes,Exampled by Polycarbonates,Polyoxalates and Polymalonates

The application of solid polymer electrolytes (SPEs) in all-solid-state(ASS) batteries is hindered by lower Li⁺-conductivity and narrower electrochemical window. Here, three families of ester-based F-modified SPEs of poly-carbonate (PCE), poly-oxalate (POE) and poly-malonate (PME) were investigated. The Li⁺-conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li⁺, the Li⁺-conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl-units are observed more effective than −O−CH₂−CF₂−CF₂−CH₂−O− during the in situ passivation of Li-metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li-metal and high-voltage-cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl-group in malonate and the suppression of enol isomerization. The coordinating capability with Li⁺, molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.     

Synthesis and electrochemical properties of individual isomers of isocyanurate-substituted bis-organodiazadihomofullerenes

The reactions of fullerene C₆₀ with isocyanurate-substituted azides afforded individual regioisomers of bis-adducts. The structures of the regioisomers depend on the structure of the organic fragment in azide and are determined primarily by the bulkiness of this fragment. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 672–677, April, 2006.