排序方式: 共有74条查询结果,搜索用时 46 毫秒
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(38):11692-11696
Neutral mesoionic carbenes (MICs) have emerged as an important class of carbene, however they are found in the free form or ligated to only a few d‐block ions. Unprecedented f‐block MIC complexes [M(N′′)3{CN(Me)C(Me)N(Me)CH}] (M=U, Y, La, Nd; N′′=N(SiMe3)2) are reported. These complexes were prepared by a formal 1,4‐proton migration reaction when the metal triamides [M(N′′)3] were treated with the N‐heterocyclic olefin H2C=C(NMeCH)2, which constitutes a new, general way to prepare MIC complexes. Quantum chemical calculations on the 5f3 uranium(III) complex suggest the presence of a U=C donor‐acceptor bond, composed of a MIC→U σ‐component and a U(5f)→MIC(2p) π‐back‐bond, but for the d0f0 Y and La and 4f3 Nd congeners only MIC→M σ‐bonding is found. Considering the generally negligible π‐acidity of MICs, this is surprising and highlights that greater consideration should possibly be given to recognizing MICs as potential π‐acid ligands when coordinated to strongly reducing metals. 相似文献
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Feriel Rekhroukh Rmy Brousses Abderrahmane Amgoune Didier Bourissou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(4):1282-1285
Migratory insertion of alkenes into gold–carbon bonds, a fundamental yet unprecedented organometallic transformation, has been investigated from a discrete (P,C) cyclometalated gold(III) dimethyl complex. Methide abstraction by B(C6F5)3 is shown to generate a highly reactive cationic AuIII complex that evolves spontaneously by C6F5 transfer from boron. In the presence of norbornene, migratory insertion into the Au C bond proceeds readily. The resulting norbornyl complex is efficiently trapped with pyridines or chloride to give stable four‐coordinate adducts. 相似文献
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Yinna Na Prof. Changle Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):8027-8033
The incorporation of comonomers during ethylene polymerization can efficiently modulate important material properties of the polyolefins. Utilizing bioresourced comonomers for the generation of high-performance polyolefin materials is attractive from a sustainability point of view. In this contribution, bioresourced eugenol and related comonomers were incorporated into polyolefins through palladium-catalyzed copolymerization and terpolymerization reactions. Importantly, high-molecular-weight catechol-functionalized polyolefins can be generated. The introduction of different metal ions induces efficient interactions with the incorporated catechol groups, leading to enhanced mechanical properties and self-healing properties. Moreover, the catechol functionality can greatly improve other properties such as surface properties, adhesion properties, and compatibilizing properties. The catechol-functionalized polyolefin was demonstrated as a versatile platform polymer for accessing various materials with dramatically different properties. 相似文献
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库仑法测定油品的烯烃含量 总被引:2,自引:0,他引:2
本文提出了由油品平均分子量和溴值计算油品的烯烃百分含量的方法。当油品中含有较多C_8以上烯烃作库命分析时,建议使用具有催化作用的电解液。文中考察了方法的准确度和精密度,并讨论了影响准确度的主要因素。该法具有简单快速、准确精密,样品用量少等优点。 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(33):10018-10022
A RhII‐catalyzed direct and stereospecific N ‐H‐ and N ‐alkyl aziridination of olefins is reported that uses hydroxylamine‐O ‐sulfonic acids as inexpensive, readily available, and nitro group‐free aminating reagents. Unactivated olefins, featuring a wide range of functional groups, are converted into the corresponding N ‐H or N ‐alkyl aziridines in good to excellent yields. This operationally simple, scalable transformation proceeds efficiently at ambient temperature and is tolerant towards oxygen and trace moisture. 相似文献
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Qingxiang Cao Jie Luo Xiaodan Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1329-1333
An unprecendented chiral sulfide catalyzed desymmetrizing enantioselective chlorination is disclosed. Various aryl‐tethered diolefins and diaryl‐tethered olefins afforded teralins and tricyclic hexahydrophenalene derivatives, respectively, bearing multiple stereogenic centers in high yields with excellent enantio‐ and diastereoselectivities. In contrast, the tertiary amine catalyst (DHQD)2PHAL led to a diastereomeric product. The products could be transformed into a variety of compounds, such as spiro‐N‐heterocycles. 相似文献