共查询到20条相似文献,搜索用时 31 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(10):2816-2819
Complex [PtMe2(PMe2Ar )] ( 1 ), which contains a tethered terphenyl phosphine (Ar =2,6‐(2,6‐i Pr2C6H3)2C6H3), reacts with [H(Et2O)2]BArF (BArF−=B[3,5‐(CF3)2C6H3]4−) to give the solvent (S) complex [PtMe(S)(PMe2Ar )]+ ( 2⋅S ). Although the solvent molecule is easily displaced by a Lewis base (e.g., CO or C2H4) to afford the corresponding adducts, treatment of 2⋅S with C2H2 yielded instead the allyl complex [Pt(η3‐C3H5)(PMe2Ar )]+ ( 6 ) via the alkyne intermediate [PtMe(η2‐C2H2)(PMe2Ar )]+ ( 5 ). Deuteration experiments with C2D2, and kinetic and theoretical investigations demonstrated that the conversion of 5 into 6 involves a PtII‐promoted HC≡CH to :C=CH2 tautomerization in preference over acetylene migratory insertion into the Pt−Me bond. 相似文献
2.
Thomas Gasevic Dr. Marcel Bamberg Julius Wicke Dr. Michael Bolte Dr. Alexander Virovets Dr. Hans-Wolfram Lerner Prof. Dr. Stefan Grimme Dr. Andreas Hansen Prof. Dr. Matthias Wagner Dr. Markus Bursch 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(6):e202314238
A joint theoretical and experimental study on 32 endohedral silafullerane derivatives [X@Si20Y20]− (X=F-I; Y=F-I, H, Me, Et) and -[Cl@Si20H12Y8]− (Y=F-I) is presented. First, we evaluated the structure-determining template effect of Cl− in a systematic series of concave silapolyquinane model systems. Second, we investigated the X−→Si20 interaction energy ( ) as a function of X− and Y and found the largest values for electron-withdrawing exohedral substituents Y. Given that X− ions can be considered as Lewis bases and empty Si20Y20 clusters as Lewis acids, we classify our inseparable host–guest complexes [X@Si20Y20]− as “confined Lewis pairs”. Third, 35Cl NMR spectroscopy proved to be highly diagnostic for an experimental assessment of the Cl−→Si20 interaction as the paramagnetic shielding and, in turn, (35Cl) of the endohedral Cl− ion correlate inversely with . Finally, we disclose the synthesis of [PPN][Cl@Si20Y20] (Y=Me, Et, Br) and provide a thorough characterization of these new silafulleranes. 相似文献
3.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):11034-11039
The encumbered tetraisocyanide dianion Na2[Fe(CNAr )4] reacts with two molecules of CO2 to effect reductive disproportionation to CO and carbonate ([CO3]2−). When the reaction is performed in the presence of silyl triflates, reductive disproportionation is arrested by silylative esterification of a mono‐CO2 adduct. This results in the formation of four‐coordinate terminal iron carbynes possessing an aryl carbamate substituent owing to the direct attachment of an C(O)OSiR3 group to an isocyanide nitrogen atom. Crystallographic, spectroscopic, and computational analyses of these iron–carbon multiply bonded species reveal electronic structure properties indicative of a conformationally locked iron carbyne unit. 相似文献
4.
Dr. Jian Zhang Chuanbao Shang Prof. Zhe An Dr. Yanru Zhu Prof. Hongyan Song Prof. Zhigang Chai Dr. Xin Shu Prof. Lirong Zheng Prof. Jing He 《Angewandte Chemie (International ed. in English)》2023,62(44):e202312068
Carbonylation of ethanol with CO2 as carbonyl source into value-added esters is of considerable significance and interest, while remains of great challenge due to the harsh conditions for activation of inert CO2 in that the harsh conditions result in undesired activation of α-C−H and even cleavage of C−C bond in ethanol to deteriorate the specific activation of O−H bond. Herein, we propose a photo-thermal cooperative strategy for carbonylation of ethanol with CO2, in which CO2 is activated to reactive CO via photo-catalysis with the assistance of *H from thermally-catalyzed dissociation of alcoholic O−H bond. To achieve this proposal, an interfacial site and oxygen vacancy both abundant SrTiCuO3-x supported Cu2O (Cu2O-SrTiCuO3-x) has been designed. A production of up to 320 μmol g−1 h−1 for ethyl formate with a selectivity of 85.6 % to targeted alcoholic O−H activation has been afforded in photo-thermal assisted gas-solid process under 3.29 W cm−1 of UV/Vis light irradiation (144 °C) and 0.2 MPa CO2. In the photo-driven activation of CO2 and following carbonylation, CO2 activation energy decreases to 12.6 kJ mol−1, and the cleavage of alcoholic α-C−H bond has been suppressed. 相似文献
5.
6.
Hongyang Su Lanlan Chen Yizhen Chen Prof. Rui Si Yuting Wu Xiaonan Wu Dr. Zhigang Geng Prof. Wenhua Zhang Prof. Jie Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20591-20596
Efforts have been devoted to achieving a highly efficient artificial synthesis of ammonia (NH3). Reported herein is a novel Fe-MoS2 catalyst with Fe atomically dispersed onto MoS2 nanosheets, imitating natural nitrogenase, to boost N2 electroreduction into NH3 at room temperature. The Fe-MoS2 nanosheets exhibited a faradic efficiency of 18.8 % with a yield rate of 8.63 μg mgcat.−1 h−1 for NH3 at −0.3 V versus the reversible hydrogen electrode. The mechanism study revealed that the electroreduction of N2 was promoted and the competing hydrogen evolution reaction was suppressed by decorating the edge sites of S in MoS2 with the atomically dispersed Fe, resulting in high catalytic performance for the electroreduction of N2 into NH3. This work provides new ideas for the design of catalysts for N2 electroreduction and strengthens the understanding about N2 activation over Mo-based catalysts. 相似文献
7.
Qiu-Jin Wu Dr. Duan-Hui Si Prof. Pan-Pan Sun Yu-Liang Dong Song Zheng Qian Chen Shi-Hua Ye Prof. Di Sun Prof. Rong Cao Prof. Yuan-Biao Huang 《Angewandte Chemie (International ed. in English)》2023,62(36):e202306822
We propose an effective highest occupied d-orbital modulation strategy engendered by breaking the coordination symmetry of sites in the atomically precise Cu nanocluster (NC) to switch the product of CO2 electroreduction from HCOOH/CO to higher-valued hydrocarbons. An atomically well-defined Cu6 NC with symmetry-broken Cu−S2N1 active sites (named Cu6(MBD)6, MBD=2-mercaptobenzimidazole) was designed and synthesized by a judicious choice of ligand containing both S and N coordination atoms. Different from the previously reported high HCOOH selectivity of Cu NCs with Cu−S3 sites, the Cu6(MBD)6 with Cu−S2N1 coordination structure shows a high Faradaic efficiency toward hydrocarbons of 65.5 % at −1.4 V versus the reversible hydrogen electrode (including 42.5 % CH4 and 23 % C2H4), with the hydrocarbons partial current density of −183.4 mA cm−2. Theoretical calculations reveal that the symmetry-broken Cu−S2N1 sites can rearrange the Cu 3d orbitals with as the highest occupied d-orbital, thus favoring the generation of key intermediate *COOH instead of *OCHO to favor *CO formation, followed by hydrogenation and/or C−C coupling to produce hydrocarbons. This is the first attempt to regulate the coordination mode of Cu atom in Cu NCs for hydrocarbons generation, and provides new inspiration for designing atomically precise NCs for efficient CO2RR towards highly-valued products. 相似文献
8.
Dr. Qiming Sun Dr. Benjamin W. J. Chen Dr. Ning Wang Prof. Qian He Dr. Albert Chang Prof. Chia-Min Yang Dr. Hiroyuki Asakura Prof. Tsunehiro Tanaka Max J. Hülsey Prof. Chi-Hwa Wang Prof. Jihong Yu Prof. Ning Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20358-20366
A CO2-mediated hydrogen storage energy cycle is a promising way to implement a hydrogen economy, but the exploration of efficient catalysts to achieve this process remains challenging. Herein, sub-nanometer Pd–Mn clusters were encaged within silicalite-1 (S-1) zeolites by a ligand-protected method under direct hydrothermal conditions. The obtained zeolite-encaged metallic nanocatalysts exhibited extraordinary catalytic activity and durability in both CO2 hydrogenation into formate and formic acid (FA) dehydrogenation back to CO2 and hydrogen. Thanks to the formation of ultrasmall metal clusters and the synergic effect of bimetallic components, the PdMn0.6@S-1 catalyst afforded a formate generation rate of 2151 molformate molPd−1 h−1 at 353 K, and an initial turnover frequency of 6860 mol molPd−1 h−1 for CO-free FA decomposition at 333 K without any additive. Both values represent the top levels among state-of-the-art heterogeneous catalysts under similar conditions. This work demonstrates that zeolite-encaged metallic catalysts hold great promise to realize CO2-mediated hydrogen energy cycles in the future that feature fast charge and release kinetics. 相似文献
9.
Dr. Manabu Nakaya Dr. Wataru Kosaka Prof. Dr. Hitoshi Miyasaka Yuki Komatsumaru Dr. Shogo Kawaguchi Dr. Kunihisa Sugimoto Dr. Yingjie Zhang Dr. Masaaki Nakamura Leonard F. Lindoy Prof. Dr. Shinya Hayami 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10745-10752
CO2-responsive spin-state conversion between high-spin (HS) and low-spin (LS) states at room temperature was achieved in a monomeric cobalt(II) complex. A neutral cobalt(II) complex, [CoII(COO-terpy)2]⋅4 H2O ( 1⋅4 H2O ), stably formed cavities generated via π–π stacking motifs and hydrogen bond networks, resulting in the accommodation of four water molecules. Crystalline 1⋅4 H2O transformed to solvent-free 1 without loss of porosity by heating to 420 K. Compound 1 exhibited a selective CO2 adsorption via a gate-open type of the structural modification. Furthermore, the HS/LS transition temperature (T1/2) was able to be tuned by the CO2 pressure over a wide temperature range. Unlike 1 exhibits the HS state at 290 K, the CO2-accomodated form 1⊃CO2 (P =110 kPa) was stabilized in the LS state at 290 K, probably caused by a chemical pressure effect by CO2 accommodation, which provides reversible spin-state conversion by introducing/evacuating CO2 gas into/from 1 . 相似文献
10.
The β‐Agostic Structure in (C5Me5)2Sc(CH2CH3): Solid‐State NMR Studies of (C5Me5)2Sc−R (R=Me,Ph, Et)
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(30):9664-9667
Multinuclear solid‐state NMR studies of Cp*2Sc−R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc−Et complex contains a β‐CH agostic interaction. The static central transition 45Sc NMR spectra show that the quadrupolar coupling constants (Cq) follow the trend of Ph≈Me>Et, indicating that the Sc−R bond is different in Cp*2Sc−Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc−CH2CH3 is related to coupling between the filled σC‐C orbital and the vacant orbital. 相似文献
11.
Daniel E. Diaz David A. Quist Austin E. Herzog Andrew W. Schaefer Ioannis Kipouros Mayukh Bhadra Edward I. Solomon Kenneth D. Karlin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17736-17740
The dioxygen reactivity of a series of TMPA‐based copper(I) complexes (TMPA=tris(2‐pyridylmethyl)amine), with and without secondary‐coordination‐sphere hydrogen‐bonding moieties, was studied at ?135 °C in 2‐methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H‐bonded [( TMPA)CuII(O2.?)]+ cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( TMPA)CuII(N3?)]+ azido analogues were compared, and the O2.? reactivity of ligand–CuI complexes when an H‐bonding moiety is replaced by a methyl group was contrasted. A drastic enhancement in the reactivity of the cupric superoxide towards phenolic substrates as well as oxidation of substrates possessing moderate C?H bond‐dissociation energies is observed, correlating with the number and strength of the H‐bonding groups. 相似文献
12.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9215-9218
Inorganic macrocycles, based on non‐carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host–guest and supramolecular chemistry. Here we demonstrate a new high‐yielding modular approach to a broad range of trimeric and hexameric S‐ and Se‐bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(μ‐NR)]2. The method involves the in situ generation of the key intermediate [E (S )P(μ‐NR)]22−(E=S, Se) dianion, which can be reacted with electrophilic [ClP(μ‐NR)]2 to give PIII/PV hexameric rings or reacted with I2 to give trimeric PV variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air‐stable and chiral inorganic macrocycles. 相似文献
13.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(10):2743-2747
Ammonia is synthesized directly from water and N2 at room temperature and atmospheric pressure in a flow electrochemical cell operating in gas phase (half‐cell for the NH3 synthesis). Iron supported on carbon nanotubes (CNTs) was used as the electrocatalyst in this half‐cell. A rate of ammonia formation of 2.2×10−3 g m−2 h−1 was obtained at room temperature and atmospheric pressure in a flow of N2, with stable behavior for at least 60 h of reaction, under an applied potential of −2.0 V. This value is higher than the rate of ammonia formation obtained using noble metals (Ru/C) under comparable reaction conditions. Furthermore, hydrogen gas with a total Faraday efficiency as high as 95.1 % was obtained. Data also indicate that the active sites in NH3 electrocatalytic synthesis may be associated to specific carbon sites formed at the interface between iron particles and CNT and able to activate N2, making it more reactive towards hydrogenation. 相似文献
14.
Dr. Jun-Dong Yi Dr. Ruikuan Xie Prof. Zai-Lai Xie Prof. Guo-Liang Chai Prof. Tian-Fu Liu Prof. Rui-Ping Chen Prof. Yuan-Biao Huang Prof. Rong Cao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23849-23856
It is still a great challenge to achieve high selectivity of CH4 in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials of possible products and the sluggish kinetics for CO2 activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH4. Here, Cu2O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper-based metal–organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH4 with partial current density of 10.8 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode) in CO2RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH2O and *OCH3) involved in the pathway of CH4 formation are stabilized by the single active Cu2O(111) and hydrogen bonding, thus generating CH4 instead of CO. 相似文献
15.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(50):16166-16169
Materials in the family of Prussian blue analogues (C3H5N2)2K[ M (CN)6], where C3H5N2 is the imidazolium ion and M =Fe, Co, undergo two phase transitions with temperature; at low temperatures the imidazolium cations have an ordered configuration (C 2/c ), while in the intermediate‐ and high‐temperature phases (both previously reported as ) they are dynamically disordered. We show from high‐resolution powder neutron diffraction data that the high‐temperature phase has zero area thermal expansion in the ab ‐plane. Supported by Landau theory and single‐crystal X‐ray diffraction data, we re‐evaluate the space group symmetry of the intermediate‐temperature phase to . This reveals that the low‐to‐intermediate temperature transition is due to competition between two different tilt patterns of the [ M (CN)6]3− ions. Controlling the relative stabilities of these tilt patterns offers a potential means to tune the exploitable electric behaviour that arises from motion of the imidazolium guest. 相似文献
16.
Dr. Guoju Yang Dr. Sneha A. Akhade Xi Chen Dr. Yue Liu Dr. Mal‐Soon Lee Dr. Vassiliki‐Alexandra Glezakou Dr. Roger Rousseau Prof. Dr. Johannes A. Lercher 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3565-3570
The thermodynamic state of H2 adsorbed on Pt in the aqueous phase was determined by kinetic analysis of H2 reacting with D2O to HDO, HD, and D2, and by DFT‐based ab initio molecular dynamics simulations of H2 adsorption on Pt(111), Pt(110), and Pt nanoparticles. Dissociative adsorption of H2 on Pt is significantly weakened in the aqueous phase compared to adsorption at gas–solid interfaces. Water destabilizes the adsorbed H atoms, decreasing the heat of adsorption by 19–22 kJ while inducing an additional entropy loss of 50–70 J K?1. Upon dissociative adsorption of H2, the average distance of water from the Pt surface increases and the liquid adopts a structure that is more ordered than before close to the Pt surface, which limits the translation mobility of the adsorbed H atoms. The presence of hydrated hydronium ions next to the Pt surface further lowers the H?Pt bond strength. 相似文献
17.
Emil Damgaard-Møller Dr. Lennard Krause Kasper Tolborg Dr. Giovanni Macetti Dr. Alessandro Genoni Prof. Jacob Overgaard 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21389-21395
Reported here is an entirely new application of experimental electron density (EED) in the study of magnetic anisotropy of single-molecule magnets (SMMs). Among those SMMs based on one single transition metal, tetrahedral CoII-complexes are prominent, and their large zero-field splitting arises exclusively from coupling between the d and dxy orbitals. Using very low temperature single-crystal synchrotron X-ray diffraction data, an accurate electron density (ED) was obtained for a prototypical SMM, and the experimental d-orbital populations were used to quantify the dxy-d coupling, which simultaneously provides the composition of the ground-state Kramers doublet wave function. Based on this experimentally determined wave function, an energy barrier for magnetic relaxation in the range 193–268 cm−1 was calculated, and is in full accordance with the previously published value of 230 cm−1 obtained from near-infrared spectroscopy. These results provide the first clear and direct link between ED and molecular magnetic properties. 相似文献
18.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):10875-10879
Gaseous HCl as a by‐product is often produced from chlorination processes using Cl2 gas. Onsite Cl2 regeneration from HCl is highly desirable as it eliminates the need to buy new Cl2 and dispose HCl waste. A gaseous HCl electrolysis with Fe3+/Fe2+ redox‐mediated cathode is demonstrated for Cl2 regeneration. HCl is oxidized to generate Cl2 and protons in the anode while Fe3+ is reduced to Fe2+ in the cathode. Simultaneously Fe3+ is regenerated by chemical oxidation of Fe2+ by oxygen (air) that also produces water. A low operational voltage and high coulombic efficiency are achieved by using a novel composite porous membrane and hydrophobic anode. Specifically, a cell voltage of only 0.64 V is needed at the typical current density of 4 kA m−2, leading to a low energy consumption of 483 kWh per ton of Cl2 (124 kJ mol −1) which is about 50–55 % of state‐of‐the‐art HCl electrolysis processes. 相似文献
19.
Dr. Yan Zhang Dr. Margaret A. Hopkins Dr. David J. Liptrot Dr. Hamideh Khanbareh Prof. Pim Groen Xuefan Zhou Prof. Dou Zhang Yinxiang Bao Prof. Kechao Zhou Prof. Chris R. Bowen Dr. David R. Carbery 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7882-7886
We demonstrate that trimethylamine borane can exhibit desirable piezoelectric and pyroelectric properties. The material was shown to be able operate as a flexible film for both thermal sensing, thermal energy conversion and mechanical sensing with high open circuit voltages (>10 V). A piezoelectric coefficient of d33≈10–16 pC N−1, and pyroelectric coefficient of p≈25.8 μC m−2 K−1 were achieved after poling, with high pyroelectric figure of merits for sensing and harvesting, along with a relative permittivity of 6.3. 相似文献
20.
Jianyu Han Pengfei An Shuhu Liu Xiaofei Zhang Dawei Wang Yi Yuan Jun Guo Xueying Qiu Ke Hou Lin Shi Yin Zhang Shenlong Zhao Chang Long Zhiyong Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12841-12846
The single‐site catalyst (SSC) characteristic of atomically dispersed active centers will not only maximize the catalytic activity, but also provide a promising platform for establishing the structure–activity relationship. However, arbitrary arrangements of active sites in the existed SSCs make it difficult for mechanism understanding and performance optimization. Now, a well‐defined ultrathin SSC is fabricated by assembly of metal‐porphyrin molecules, which enables the precise identification of the active sites for d‐orbital energy engineering. The activity of as‐assembled products for electrocatalytic CO2 reduction is significantly promoted via lifting up the energy level of metal d orbitals, exhibiting a remarkable Faradaic efficiency of 96 % at the overpotential of 500 mV. Furthermore, a turnover frequency of 4.21 s?1 is achieved with negligible decay over 48 h. 相似文献