N-杂环卡宾及其金属络合物的性质和合成方法

由于N-杂环卡宾结构的多样性，以及它们的金属络合物良好的稳定性和催化活性，近年来受到了人们的广泛关注。本文对N-杂环卡宾及其金属络合物的性质和合成方法进行了综述。参考文献30篇。     

Rhodium(I) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks

Novel rhodium(I) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks were synthesized and the complexes were used as catalysts in rhodium-catalyzed hydrosilylation of alpha,beta-unsaturated ketones to show high 1,4-adduct selectivity.     

N-杂环卡宾金属配合物在酮硅氢加成反应中的新进展

N-杂环卡宾是一类新型催化剂和配体, 在有机化学中得到了极大的重视. N-杂环卡宾金属配合物的研究在近几年来得到迅速的发展,总结了酮硅氢加成反应中N-杂环卡宾金属配合物催化剂的应用新进展.     

二茂铁咪唑盐的合成及其在Suzuki-Miyaura反应中的应用

合成了硫醚官能化、膦官能化及未官能化的二茂铁咪唑盐,并研究了以其作为N-杂环卡宾配体前体对Pd催化的Suzuki-Miyaura偶联反应的影响,发现在4-甲基溴苯与苯硼酸偶联反应中以膦官能化的配体对催化性能提高有利,而硫醚官能化不利于催化性能提高。     

Complexes of palladium(II) with N-heterocyclic carbenes from adamantylimidazole as precatalysts for thiophene and imidazole arylation

Russian Chemical Bulletin - Complexes of palladium(II) with N-heterocyclic carbenes of the PEPPSI-type were synthesized by the reaction of PdCl2 with 1-adamantyl-3-(R-methyl)-1H-imidazolium salts....     

官能团化N,C双齿N-杂环卡宾配合物研究进展

综述了官能团化N,C双齿N-杂环卡宾金属配合物研究的最新进展,着重讨论了这些配合物对各种化学反应的催化性能.     

氮杂环卡宾在有机催化中的研究进展

介绍了氮杂环卡宾作为有机催化剂的发展历史和催化机理,综述了近年来氮杂环卡宾在有机催化领域中的研究成果.     

The double role of ionic liquids in organic electrosynthesis: Precursors of N-heterocyclic carbenes and green solvents. Henry reaction

N-heterocyclic carbenes, electrogenerated by cathodic reduction of imidazolium-based room temperature ionic liquids (RTILs), are stable bases able to catalyze the Henry reaction. Accordingly, the electrosynthesis of β-nitroalcohols has been achieved, under mild conditions and in high yields, by stirring nitromethane and aldehydes in previously electrolyzed RTILs. RTILs have been used as green solvents as well as precursors of N-heterocyclic carbenes.     

Unsymmetrically N,N'-substituted saturated carbenes: synthesis, reactivity and preparation of a rhodium(I) carbene complex

A versatile synthesis of unsymmetrically N,N'-substituted saturated carbenes is described. The novel racemic imidazolidin-2-ylidenes rac-5 have been synthesized by reductive desulfurization of the corresponding imidazolidin-2-thiones rac-4. The thiones were prepared in two reaction steps from aldimines and secondary amines. Three different substituents at N1, N3 and C4 of the five-membered N-heterocyclic ring can be introduced by choice of suitable aldimines and secondary amines. The dimerization behaviour (diaminocarbene/enetetramine equilibrium) for the unsymmetrically N,N'-substituted imidazolidin-2-ylidenes has been investigated by NMR spectroscopy. Unsymmetrically N-iPr and N-iBu substituted N-heterocyclic carbenes undergo a slow dimerization, whereas N-tBu substituted derivatives are stable as monomeric carbenes indefinitely. The carbene ligand rac-5d has been coordinated to rhodium(I) to give the square-planar rhodium carbene complex [Cl(cod)Rh(rac-5d)]rac-6d which has been characterized by an X-ray diffraction analysis.     

Carbene-Stabilized Exceptional Silicon Halides

The isolation of stable carbenes, such as N-heterocyclic carbenes, cyclic alkyl amino carbenes, and abnormal N-heterocyclic carbenes, has encouraged synthetic chemists to use them as neutral ligands for stabilizing unusual compounds with main group elements. In this Minireview, an overview is provided of the recent developments in the chemistry of carbene-stabilized silicon halides, in which the silicon atoms are in low oxidation state. The structural diversities emanating from the differences in the HOMO–LUMO gaps of various carbenes will also be discussed.     

Anionic N-heterocyclic carbenes by decarboxylation of sydnone-4-carboxylates

Unstable N-heterocyclic carbenes can be masked and stabilized as pseudo-cross-conjugated hetarenium-carboxylates which decarboxylate on warming. This study deals with the decarboxylation of carboxylates of mesoionic compounds to generate anionic N-heterocyclic carbenes. Lithium sydnone-4-carboxylates were therefore prepared via 4-bromosydnones by halogen-lithium exchange with nBuLi and subsequent treatment with carbon dioxide. Protonation gave the corresponding sydnone-4-carboxylic acids. Thermogravimetric measurements in addition to temperature dependent IR spectroscopy proved the decarboxylation of lithium sydnone-4-carboxylates and formation of the corresponding sydnone anions which can be represented as anionic N-heterocyclic carbenes. In DMSO-d6 solution, water favors the decarboxylation. Calculations have been performed to elucidate the mechanism of the decarboxylation in the absence and presence of water.     

Imidazo[1,5-a]pyridine: a versatile architecture for stable N-heterocyclic carbenes

The imidazo[1,5-a]pyridine skeleton provides a versatile platform for the generation of new types of stable N-heterocyclic carbenes. Rh(I) mono- (6) and biscarbenes (7) from imidazo[1,5-a]pyridin-3-ylidenes (ImPy) and derivatives such as 13 from a mesoionic carbene were synthesized and characterized.     

Pd-PEPPSI complexes based on 1,2,4-triazol-3-ylidene ligands as efficient catalysts in the Suzuki—Miyaura reaction

The palladium complexes of the Pd-PEPPSI type with N-heterocyclic carbenes of the 1,2,4-triazole series were synthesized in 76—99% yields by the reactions of PdCl₂ with 1,4-di- alkyl-1,2,4-triazolium salts in pyridine in the presence of KBr or KI as sources of halide ions and tetrabutylammonium salts as phase-transfer catalysts. The obtained complexes can be used as efficient catalysts for the Suzuki—Miyaura cross-coupling and are not inferior to the commercially available Pd-PEPPSI catalysts in activity.     

Synthetic and Structural Studies of N-Heterocyclic Carbene Complexes of Nickel

Transition metal complexes of stable N-heterocyclic carbenes have recently gained increasing attention as pre-catalysts for a number of important reactions primarily based on the analogy between N-heterocyclic carbenes and strong ó-donating tertiary phosphines,[1] Although a large number of transition-metal carbene complexes have been reported, very few incorporate chelating carbenes were reported.[2,3] Therefore, we have set out to prepare and study transition-metal compounds with chelating di-N-heterocyclic carbenes, and we now report new dicationic tetra(carbine)nickel(Ⅱ) complexes in this class (Scheme 1). Their structures have been determined by single-crystal X-ray diffraction studies (Figure 1).     

N-杂环卡宾: 一种多用途有机小分子催化剂

近年来, N-杂环卡宾化学引起了化学家们广泛的研究兴趣, 这一切主要归功于Arduengo等的杰出工作, 在1991年他们首次成功分离得到了第一个稳定的N-杂环卡宾——咪唑-2-碳烯. 这推动了N-杂环卡宾化学的飞速发展. 尽管N-杂环卡宾作为配体在金属有机化学中已经被广泛研究, 然而, 对N-杂环卡宾作为反应底物和有机小分子催化剂的研究还有待进一步深入. N-杂环卡宾作为有机小分子催化剂在有机反应中的应用及其研究进展, 引起有机化学家对N-杂环卡宾化学这一热点领域的更多关注.     

Intramolecular cyclization and subsequent rearrangements of alkyne-tethered N-heterocyclic carbenes

Alkyne-tethered imidazole and 1,2,4-triazole-based N-heterocyclic carbene precursors have been prepared and studies of the intramolecular reactions of carbenes are performed. Products consistent with intramolecular cyclizations and subsequent rearrangements were observed. Mechanistic studies using crossover experiments showed that the products did arise from intramolecular carbene additions. The reactions are proposed to go through vinylogous diaminocarbene intermediates similar to vinylogous dialkoxycarbenes formed during Boger cycloaddition reactions. Imidazole substituted dienes were observed to be the major products of tandem cyclization and elimination reactions that were observed for imidazole-based N-heterocyclic carbenes.     

A highly stable N-heterocyclic carbene complex of trichloro-oxo-vanadium(V) displaying novel Cl-Ccarbene bonding interactions

Reaction of 1,3-dimesitylimidazol-2-ylidene and trichloro-oxo-vanadium(V) yields an air stable 1:1 adduct, which demonstrates the utility of N-heterocyclic carbenes to stabilize metal complexes in high oxidation states. The molecular structure of this compound reveals that the chloride ligands cis to the carbene are oriented toward the Ccarbene atom. Density functional theory calculations show that a bonding interaction occurs between lone pairs of these chlorides and the formally unoccupied p-orbital of the carbene. Previous studies indicated that this orbital was not involved in the bonding of N-heterocyclic carbenes to transition metals. The observed interaction therefore represents a new bonding mode for these widely used ligands.     

Heterocyclic carbenes: synthesis and coordination chemistry

The chemistry of heterocyclic carbenes has experienced a rapid development over the last years. In addition to the imidazolin-2-ylidenes, a large number of cyclic diaminocarbenes with different ring sizes have been described. Aside from diaminocarbenes, P-heterocyclic carbenes, and derivatives with only one, or even no heteroatom within the carbene ring are known. New methods for the synthesis of complexes with N-heterocyclic carbene ligands such as the oxidative addition or the metal atom template controlled cyclization of beta-functionalized isocyanides have been developed recently. This review summarizes the new developments regarding the synthesis of N-heterocyclic carbenes and their metal complexes.     

含吡啶鎓阳离子的氮杂环卡宾Pd(Ⅱ)配合物的合成、结构及催化性能

合成了四个含吡啶鎓阳离子的氮杂环卡宾钯(II)三碘配合物. 通过核磁共振谱和元素分析对它们进行了表征. 同时利用X射线单晶衍射确定了其中两个配合物的晶体结构. 研究表明该系列配合物对Suzuki-Miyaura偶联具有催化活性.     

Triazene formation via reaction of imidazol-2-ylidenes with azides

Treatment of N-heterocyclic carbenes (as their free carbenes or generated in situ) with alkyl, aryl, acyl or tosyl azides afforded the respective substituted triazenes in excellent yields.