Dihydrogen bond and X–H…σ interaction as sub‐classes of hydrogen bond

Dihydrogen bond (DHB) and X–H…σ interaction are discussed and compared here. Both interactions possess numerous characteristics of the hydrogen bond (HB). The Natural Bond Orbitals method results show that σ → σ* is the most important interaction connected with the electron charge transfer from the Lewis base to the Lewis acid for the DHB as well as for the X–H…σ HB. However, there are distinct differences between these interactions, and this is evident from the analysis based on the Quantum Theory of Atoms in Molecules as well as from the decomposition of the energy of interaction. The X–H…π interaction is also discussed here since it possesses few characteristics typical for the X–H…σ interaction and not for the DHB. Copyright © 2013 John Wiley & Sons, Ltd.     

磷酸二氢铵水溶液构型能和径向分布函数的分子动力学模拟

采用分子动力学模拟对不同温度下磷酸二氢铵水溶液的构型能和径向分布函数进行了研究．磷酸二氢根被看作七节点模型,铵离子被看作五节点模型,而水分子则被看作简单点电荷模型．在饱和温度 附近,体系局域粒子数密度有波动．373?400 K的溶液势能增长缓慢表明磷酸二氢铵部分分解．磷酸二氢根中的氧原子与铵离子中氢原子的径向分布函数在三种不同温度下呈现明显不同,表明溶液中平均氢键数目随温度的变化明显改变．温度对磷酸二氢根中的氢原子和氧原子的结合有一定的影响,而在饱和溶液中有更多的生长基元产生．     

Copper immobilized on aminated ferrite nanoparticles by 2‐aminoethyl dihydrogen phosphate (Fe3O4@AEPH2‐CuII) catalyses the conversion of aldoximes to nitriles

Cu^II immobilized on aminated ferrite nanoparticles by 2‐aminoethyl dihydrogen phosphate (Fe₃O₄@AEPH₂‐Cu^II) was prepared and characterized using FT‐IR, TGA, TEM, EDX, VSM, XRD, CHN and ICP techniques. The easily prepared heterogeneous nanocatalyst demonstrated a significant catalytic performance for the transformation of aldoximes to nitriles that is far superior to previously reported methods. The reaction allows for the conversion of a wide variety of aldoximes including aromatic, aliphatic and heterocyclic aldoximes in good to excellent yields (50–98%). High efficiency, mild reaction conditions, easy work‐up, operational simplicity, simple purification of products and safe handling of the catalyst are important advantages of this method. In addition, the environmentally benign heterogeneous nanocatalyst can be easily recovered from reaction mixtures using an external magnet and reused several times without any loss of activity. Copyright © 2015 John Wiley & Sons, Ltd.     

In situ measurement of growth kinetics of {100} KDP crystal faces in the presence of polyphosphate impurities

The face growth rate and critical supersaturation of {100} face were in situ measured using the laser‐polarization‐interference technique in the presence of potassium pyrophosphate, trimetric sodium phosphate and sodium hexametaphosphate impurities. The polyphosphate impurities inhibit the growth rate of prismatic faces. The face growth rate as a function of supersaturation at different impurity concentrations, as well as critical supersaturation as a function of impurity concentrations, was found in good agreement with a two‐dimensional nucleation model in the pure system and Kubota and Mullin's model in the presence of impurities. The average distance L between active sites available for impurity adsorption as well as the edge free energy was calculated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

三聚磷酸二氢铝与有机胺的插层反应特征

采用IR、XRD、SEM、EDS、DT-TG和滴定实验等技术手段研究主体三聚磷酸二氢铝(ATP)与客体甲胺、乙胺、正丙胺和正丁胺等有机胺的插层反应特性。 实验结果表明,ATP与甲胺、乙胺、正丙胺、正丁胺发生了化学反应,有机胺中的N与ATP层间-OH上的H形成配位键。 这些有机胺通过插层反应改变了ATP的酸性、层间距和热分解温度,但没有改变颗粒的层状形貌。 层间距从0.795 nm增大至1.71 nm,层间距d与有机胺的碳原子数Cn呈线性关系：d=0.229Cn+0.811,R2=0.9986。 有机胺分子链越长则越具有剥离倾向。     

Dihydrogen Activation with a Neutral,Intermolecular Silicon(IV)-Amine Frustrated Lewis Pair

The heterolytic cleavage of dihydrogen constitutes the hallmark reaction of frustrated Lewis pairs (FLP). While being well-established for planar Lewis acids, such as boranes or silylium ions, the observation of the primary H₂ splitting products with non-planar Lewis acid FLPs remained elusive. In the present work, we report bis(perfluoro-N-phenyl-ortho-amidophenolato)silane and its application in dihydrogen activation to a fully characterized hydridosilicate. The strict design of the Lewis acid, the limited selection of the Lewis base, and the distinct reaction conditions emphasize the narrow tolerance to achieve this fascinating process with a tetrahedral Lewis acid.     

M3+(H2AsO4)(H2As2O7) (M3+ = Al,Ga) and In2(H2AsO4)2(H2As2O7)2: a new layer structure type and a new framework structure type containing the rare H2As2O72− group

The crystal structures of hydrothermally synthesized aluminium dihydrogen arsenate(V) dihydrogen diarsenate(V), Al(H₂AsO₄)(H₂As₂O₇), gallium dihydrogen arsenate(V) dihydrogen diarsenate(V), Ga(H₂AsO₄)(H₂As₂O₇), and diindium bis[dihydrogen arsenate(V)] bis[dihydrogen diarsenate(V)], In₂(H₂AsO₄)₂(H₂As₂O₇)₂, were determined from single‐crystal X‐ray diffraction data collected at room temperature. The first two compounds are representatives of a novel sheet structure type, whereas the third compound crystallizes in a novel framework structure. In all three structures, the basic building units are M ³⁺O₆ octahedra (M = Al, Ga, In) that are connected via one H₂AsO₄⁻ and two H₂As₂O₇²⁻ groups into chains, and further via H₂As₂O₇²⁻ groups into layers. In Al/Ga(H₂AsO₄)(H₂As₂O₇), these layers are interconnected by weak‐to‐medium–strong hydrogen bonds. In In₂(H₂AsO₄)₂(H₂As₂O₇)₂, the H₂As₂O₇²⁻ groups link the chains in three dimensions, thus creating a framework topology, which is reinforced by weak‐to‐medium–strong hydrogen bonds. The three title arsenates represent the first compounds containing both H₂AsO₄⁻ and H₂As₂O₇²⁻ groups.     

From Saturated BN Compounds to Isoelectronic BN/CC Counterparts: An Insight from Computational Perspective

In the present study, the inorganic analogues of alkanes as well as their isoelectronic BN/CC counterparts that bridge the gap between organic and inorganic chemistry are comparatively studied on the grounds of static DFT and Car–Parrinello molecular dynamics simulations. The BN/CC butanes CH₃CH₂BH₂NH₃, BH₃CH₂NH₂CH₃, and NH₃CH₂BH₂CH₃ were considered and compared with their isoelectronic counterparts NH₃BH₂NH₂BH₃ and CH₃CH₂CH₂CH₃. In addition, systematical replacement of the NH₂BH₂ fragment by the isoelectronic CH₂CH₂ moiety is studied in the molecules H₃N(NH₂BH₂)_3–m(CH₂CH₂)_mBH₃ (for m=0, 1, 2, or 3) and H₃N(NH₂BH₂)_2–m(CH₂CH₂)_mBH₃ (for m=0, 1, or 2). The DFT and Car–Parrinello simulations show that the isosteres of the BN/CC butanes CH₃CH₂BH₂NH₃, BH₃CH₂NH₂CH₃, and NH₃CH₂BH₂CH₃ and of larger oligomers of the type (BN)_k(CC)_l where k≥l are stable compounds. The BN/CC butane H₃NCH₂CH₂BH₃ spontaneously produces molecular hydrogen at room temperature. The reaction, prompted by very strong dihydrogen bonding NH???HB, undergoes through the neutral, hypervalent, pentacoordinated boron dihydrogen complex R?BH₂(H₂) [R=(CH₂CH₂)_nNH₂]. The calculations suggest that such intermediate and the other BN/CC butanes CH₃CH₂BH₂NH₃, BH₃CH₂NH₂CH₃, and NH₃CH₂BH₂CH₃ as well as larger BN/CC oligomers are viable experimentally. A simple recipe for the synthesis of CH₃CH₂BH₂NH₃ is proposed. The strength of the dihydrogen bonding appeared to be crucial for the overall stability of the saturated BN/CC derivatives.     

三聚磷酸二氢铝/载硫硅藻土催化合成阿司匹林

以三聚磷酸二氢铝/载硫硅藻土为催化剂,水杨酸(1)和乙酰酐(2)经酯化反应合成了阿司匹林(3),其结构经IR确证。采用单因素实验考察了反应条件对3收率的影响,实验结果表明:各因素影响顺序为:反应温度原料配比[r=n(2)∶n(1)]反应时间催化剂用量。在最佳反应条件[1 50 mmol,催化剂用量5%,r=n(2)∶n(1)=3.14,于81℃反应40 min]下,收率88.6%。催化剂经五次重复使用后收率仍达83.3%。