研究了在12种有机硼烷和铝催化剂与12种羟基引发剂的结合下,环氧丙烷(PO)的催化开环聚合反应。这些催化剂的路易斯酸度和配体空间体积不同,而引发剂的官能团和布朗斯台德酸度不同。这项研究检查了PO聚合的四个方面:聚合度控制,催化剂和引发剂结构对活性和聚合物分子量的影响,催化剂与引发剂和催化剂与单体的反应以及生成的PPO的结构。在不存在羟基引发剂的情况下,B(C 6 F 5)3主要在己烷中催化PO异构化为丙醛,另外在甲苯中产生低聚物;有趣的是,在空间上受阻的全氟联苯硼烷B(C 12 F 9)3没有提供这种异构化产物。然而,通过以[PO] 0:[-OH] 0为41.7的比例添加足够高浓度的羟基引发剂,可以制备出具有所需M n范围为几千道尔顿和低PDI <1.3的PPO。B(C 6 F 5)3 /引发剂体系。PPO M n的线性依赖性观察到单体转化率高达约84%。PO的聚合活性强烈取决于硼烷催化剂的路易斯酸度,其中B(C
Hydrogen Bonding to a Dinitrogen Complex at Room Temperature: Impacts on N<sub>2</sub> Activation
作者:James P. Shanahan、Nathaniel K. Szymczak
DOI:10.1021/jacs.9b02288
日期:2019.5.29
computational analysis of the effects of hydrogenbonding to a metal dinitrogen complex. A series of H-bond donors over a wide p Ka range (Δ 20) interact with the nitrogen unit of a ReI-(N2) complex at room temperature. Analysis by 15N NMR, IR spectroscopy, association equilibria, and DFT studies indicates that the H-bonding interaction polarizes and weakens the N-N bond. These results provide insight into
我们报告了氢键对金属二氮配合物的影响的实验和计算分析。一系列宽 p Ka 范围 (Δ 20) 上的氢键供体在室温下与 ReI-(N2) 复合物的氮单元相互作用。通过 15N NMR、IR 光谱、缔合平衡和 DFT 研究的分析表明,氢键相互作用极化并削弱了 NN 键。这些结果提供了深入了解二级球体残基在固氮酶中的作用。
Lewis Acidic Boranes, Lewis Bases, and Equilibrium Constants: A Reliable Scaffold for a Quantitative Lewis Acidity/Basicity Scale
作者:Robert J. Mayer、Nathalie Hampel、Armin R. Ofial
DOI:10.1002/chem.202003916
日期:2021.2.24
borane/Lewis base combination through the sum of two descriptors, one for Lewis acidity (LAB) and one for Lewis basicity (LBB). The resulting Lewis acidity/basicity scale is independent of fixed reference acids/bases and valid for various types of trivalent boron‐centered Lewisacids. It is demonstrated that the newly developed Lewis acidity/basicity scale is easily extendable through linear relationships with
基于三芳基硼烷与各种以 O、N、S 和 P 为中心的路易斯碱在二氯甲烷中反应的 90 个实验平衡常数,开发了针对以硼为中心的路易斯酸的定量路易斯酸度/碱度标度。 20℃。使用线性自由能关系 log K B = LA B + LB B进行分析,可以通过两个描述符(一个用于路易斯酸度 ( LA B ))的总和来计算任何类型的硼烷/路易斯碱组合的平衡常数K B。一个用于路易斯碱度(LB B)。所得的路易斯酸度/碱度标度与固定的参考酸/碱无关,并且对于各种类型的三价硼中心路易斯酸有效。事实证明,新开发的路易斯酸度/碱度标度可以通过与量子化学计算或常见的物理有机描述符和已知热力学数据(Δ H )的线性关系轻松扩展。此外,该实验平台可用于硼烷催化反应的合理发展。
Tris(2,4,6-trifluorophenyl)borane: An Efficient Hydroboration Catalyst
作者:James R. Lawson、Lewis C. Wilkins、Rebecca L. Melen
DOI:10.1002/chem.201703109
日期:2017.8.16
The metal‐free catalyst tris(2,4,6‐trifluorophenyl)borane has demonstrated its extensive applications in the 1,2‐hydroboration of numerous unsaturated reagents, namely alkynes, aldehydes and imines, consisting of a wide array of electron‐withdrawing and donating functionalities. A range of over 50 borylated products are reported, with many reactions proceeding with low catalyst loading under ambient
Stoichiometric and Catalytic C−C and C−H Bond Formation with B(C<sub>6</sub>
F<sub>5</sub>
)<sub>3</sub>
via Cationic Intermediates
作者:Yashar Soltani、Lewis C. Wilkins、Rebecca L. Melen
DOI:10.1002/anie.201704789
日期:2017.9.18
concomitant C−H or C−C bondformation. The activation of alkyne‐containing substrates with B(C6F5)3 enabled the first catalytic intramolecular cyclizations of carboxylic acid substrates using this Lewis acid. In addition, intramolecular cyclizations of esters enable C−C bondformation as catalytic B(C6F5)3 can be used to effect formal 1,5‐alkyl migrations from the ester functional groups to unsaturated carbon–carbon
这项工作展示了一种新的催化环化反应,该反应使用高度路易斯酸的硼烷并伴有CH或CC键的形成。用B(C 6 F 5)3活化含炔的底物使得能够使用该路易斯酸对羧酸底物进行第一个催化的分子内环化反应。此外,酯的分子内环化使CC键形成为催化性B(C 6 F 5)3。可用于实现从酯官能团到不饱和碳-碳骨架的正式1,5-烷基迁移。该无金属方法用于在相对温和的条件下以极高的收率和极好的原子效率催化形成复杂的二氢吡喃酮和异香豆素。
Synthesis and photophysical properties of imine borane adducts towards vapochromic materials
作者:Yashar Soltani、Samuel J. Adams、Jennifer Börger、Lewis C. Wilkins、Paul D. Newman、Simon J. A. Pope、Rebecca L. Melen
DOI:10.1039/c8dt03019g
日期:——
A series of alkynyl aryl conjugated aldehydes and imines were prepared and their adducts with various Lewis acidic boranes have been studied via NMR, absorption, and luminescence spectroscopies in solution. The imine-B(C6F5)3 adduct showed remarkable solution stability, and was then trialled in vapochromism experiments using simple impregnated paper strips to examine the fluorescence responses.
制备了一系列炔基芳基共轭醛和亚胺,并通过NMR,吸收和发光光谱法研究了它们与各种路易斯酸性硼烷的加合物。亚胺-B(C 6 F 5)3加合物显示出显着的溶液稳定性,然后使用简单的浸渍纸条在光致变色实验中进行了试验,以检查荧光响应。