四坐标的化 (I) 单化物:可逆的二结合,结合激活和脱质化
Matthew D Millard1, Curtis E Moore, Arnold L Rheingold
1Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093-0358, USA.
Journal of the American Chemical Society
|June 17, 2010
概括
这项研究成功地隔离和表征了难以捉摸的四坐标的 (((I) 单化物复合物,使用了固态阻碍的素联结体. 这些发现为以前假设的化学转化中的反应性物种提供了具体的证据.
科学领域:
- 有机金属化学 有机金属化学
- 协调化学 协调化学
- 催化剂研究 催化剂研究
背景情况:
- 四坐标的 ((I) 单化物复合物被认为是各种化学反应中的反应性中间体.
- 以前试图隔离这些物种的尝试因其固有的不稳定性而受到阻碍.
- 强大的配体的发展对于稳定过渡性有机金属物种至关重要.
研究的目的:
- 合成和表征可分离的四坐标的 (((I) 单化物复合物.
- 提供关于这些难以捉摸的物种存在的最终证据.
- 为了探索这些复合物的反应性和稳定性,使用固态阻碍的氨酸连接体.
主要方法:
- 使用甲基亚丹替代酸联体 (L(mAd)) 合成复合物.
- 二化前体与有机金属试剂 (PhMgBr,Li[HBEt(3)) 的反应.
- 在各种条件下进行光谱表征 (NMR) 和反应性研究 (N(2),H(2),H(2) O,Li[12-c-4]).
主要成果:
- 隔离一个正方形平面的 ((I) 单化合物复合物,HIr ((N ((2)) ((L ((mAd)) ((2),和一个三化合物复合物,H ((3)) ((L ((mAd)) ((2)).
- 观察了HIr (N) 2 (L) 2 (mAd) 2及其环金属化形式H (Ir) 2 (kappa) -P,C-L (mAd) 2 (L) 3 (mAd) 的平衡状态.
- 产生五化物和二化物氧化物复合物,分别与H(2) 和H(2) O反应.
- 形成一个稳定的四坐标的Ir(I) 单化盐,[Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))))) 的形成.
结论:
- 使用固态阻碍的L ((mAd) 接体使得以前难以捉摸的四坐标 (I) 单化合物的分离成为可能.
- 这些复合物表现出独特的反应性,在不同的反应条件下形成各种水化物种.
- 该研究为研究这些重要的有机金属中间体的基本化学物质提供了一个稳定的平台.
相关概念视频
Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
Woodward–Hoffmann Selection Rules and Microscopic Reversibility
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
Aldehydes and Ketones with Amines: Imine Formation Mechanism
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
Diazonium Group Substitution: –OH and –H
Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.


