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991.
Linfeng Chen Michael J. Turo Milan Gembicky Ruth A. Reinicke Alina M. Schimpf 《Angewandte Chemie (International ed. in English)》2020,59(38):16609-16615
The Preyssler polyoxoanion, [NaP5W30O110]14? ({P5W30}), is used as a platform for evaluating the role of nonbridging cations in the formation of transition‐metal‐bridged polyoxometalate (POM) coordination frameworks. Specifically, the assembly architecture of Co2+‐bridged frameworks is shown to be dependent on the identity and amount of alkali or alkaline‐earth cations present during crystallization. The inclusion of Li+, Na+, K+, Mg2+, or Ca2+ in the framework synthesis is used to selectively synthesize five different Co2+‐bridged {P5W30} structures. The influence of the competition between K+ and Co2+ for binding to {P5W30} in dictating framework assembly is evaluated. The role of ion pairing on framework assembly structure and available void volume is discussed. Overall, these results provide insight into factors governing the ability to achieve controlled assembly of POM‐based coordination networks. 相似文献
992.
Devin H. A. Boom Ewoud J. J. de Boed Emmanuel Nicolas Martin Nieger Andreas W. Ehlers Andrew R. Jupp J. Chris Slootweg 《无机化学与普通化学杂志》2020,646(13):586-592
The reaction of the intramolecular frustrated Lewis pair (FLP) tBu2PCH2BPh2 with the amine-boranes NH3 · BH3 and Me2NH · BH3 leads to the formation of the corresponding FLP-H2 adducts as well as novel five-membered heterocycles that result from capturing the in situ formed amino-borane by a second equivalent of FLP. The sterically more demanding tBu2PCH2BMes2 does not form such a five-membered heterocycle when reacted with Me2NH · BH3 and its H2 adduct liberates dihydrogen at elevated temperatures, promoting the metal-free catalytic dehydrogenation of amine-boranes. 相似文献
993.
Dr. Daisuke Uraguchi Fumito Ueoka Dr. Naoya Tanaka Dr. Tomohito Kizu Wakana Takahashi Prof. Dr. Takashi Ooi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11553-11558
Catalysis by chiral weakly-coordinating anions (WCAs) remains underdeveloped due to the lack of a molecular design strategy for exploiting their characteristics, such as the non-nucleophilic nature. Here, we report the development of a chiral borate ion comprising an O,N,N,O-tetradentate backbone, which ensures hitherto unattainable structural robustness. Upon pairing with a proton, the hydrogen borate acts as an effective catalyst for the asymmetric Prins-type cyclization of vinyl ethers, providing access to structurally and stereochemically defined dihydropyrans. The key to selectivity control is the distinct ability of the borate ion to discriminate the prochiral faces of the acyclic oxonium ion intermediate and dictate the regiochemical outcome. We anticipate that this study paves the way for exploring the untapped potential of WCA catalysis for selective chemical synthesis. 相似文献
994.
995.
利用外微分形式系统和Lie代数表示理论提出了求解非线性波方程Lax对的延拓结构理论,该方法是构造非线性波方程Lax对的系统最有效的方法.其关键在于如何给出延拓代数的具体表示,如微分算子表示或矩阵表示.如果一个非线性波方程具有非平凡的延拓代数,则称其延拓代数可积,本篇论文主要利用延拓结构理论,讨论KdV方程的解,同时给出... 相似文献
996.
997.
A. Sankaranarayanan 《Lithuanian Mathematical Journal》2007,47(3):277-310
We study the sixth-power moments of certain L-functions belonging to a sub-class of the Selberg’s class on the critical line and, using this, we conclude an upper bound
for the fourth-power moments of certain L-functions related to GL
3 on the critical line. This is an analogue of the upper bound for the twelfth-power moment of the Riemann zeta-function on
the critical line.
Published in Lietuvos Matematikos Rinkinys, Vol. 47, No. 3, pp. 341–380, July–September, 2007. 相似文献
998.
Starting with the group of operators on a separable Hilbert space that differ from the identity by a trace-class operator,
we construct a solution of the two-dimensional infinite Toda hierarchy associated with a maximal commutative subalgebra in
complex k×k matrices.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 155, No. 1, pp. 177–192, April, 2008. 相似文献
999.
针对浅海波导中水平线列阵接收的低频宽带低信噪比信号,提出了一种利用多拍信号相干累加来提高干涉简正波特征频谱信噪比的方法。这种方法主要针对未知距离和声源形式的运动声源,对不同时刻(或接收距离)处阵列输出信号进行WARPING变换,基于干涉简正波特征频率不变性原理,通过距离和径向速度比值的搜索来使得不同时刻或距离处信号自相关函数WARPING变换后频谱具有近似相同的特征频率,进而通过相干累加来增强信号干涉简正波特征频率。仿真和海上实验数据分析均验证了方法的性能。 相似文献
1000.
Dr. Alessandro Bismuto Dr. Gary S. Nichol Dr. Fernanda Duarte Dr. Michael J. Cowley Dr. Stephen P. Thomas 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12831-12835
The reaction of a Lewis acidic borane with an alkyne is a key step in a diverse range of main group transformations. Alkyne 1,1-carboboration, the Wrackmeyer reaction, is an archetypal transformation of this kind. 1,1-Carboboration has been proposed to proceed through a zwitterionic intermediate. We report the isolation and spectroscopic, structural and computational characterization of the zwitterionic intermediates generated by reaction of B(C6F5)3 with alkynes. The stepwise reactivity of the zwitterion provides new mechanistic insight for 1,1-carboboration and wider B(C6F5)3 catalysis. Making use of intramolecular stabilization by a ferrocene substituent, we have characterized the zwitterionic intermediate in the solid state and diverted reactivity towards alkyne cyclotrimerization. 相似文献