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1.
Merceron N Miqueu K Baceiredo A Bertrand G 《Journal of the American Chemical Society》2002,124(24):6806-6807
(Amino)(phosphino)carbenes are stable due to the donation of the nitrogen lone pair, the phosphino group remains strongly pyramidalized. Reactions can be performed selectively at the carbene center, but also at the phosphorus center leading to new stable carbenes. These difunctional molecules can be considered as hybrid ligands. 相似文献
2.
《Journal of organometallic chemistry》2005,690(24-25):5867-5875
In order to probe the ligand properties we have examined a series of Cr(CO)5L and Ni(CO)3L complexes using density functional theory (DFT). The ligands included in our study are N-heterocyclic carbenes (NHCs) and Bertrand-type carbenes. Our study shows that the carbene–metal bonds of imidazol-2-ylidenes (1), imidazolin-2-ylidenes (2), thiazo-2-ylidenes (3), and triazo-5-ylidenes (4) are significantly stronger than those of Bertrand-type carbenes (5–7). The force constants of C–O in complexes are related to the property of isolated carbenes such as proton affinity (PA), electronegativity (χ), and charge transfer (ΔN). NHCs and Bertrand-type carbenes are identified as nucleophilic, soft ligands. Carbene stabilization energy (CSE) computations indicate that carbenes 1 and 4 are the most stable species, while 2 and 3 are less stable. In contrast to NHCs, CSE of carbenes 5–7 are much smaller, and their relative stabilities are in the order (amino)(aryl) carbenes 7e–7g > (amino)(alkyl) carbenes 7a–7d > (phosphino)(aryl) 6d–6e, and (phosphino)(silyl) carbenes 5a–5c > (phosphino)(alkyl) carbenes 6a–6c. 相似文献
3.
Frey GD Song M Bourg JB Donnadieu B Soleilhavoup M Bertrand G 《Chemical communications (Cambridge, England)》2008,(39):4711-4713
Conjugate acids of cyclic (amino)(phosphino)carbenes (P-NHCs) have been prepared, and several different processes have been observed during their deprotonation, which include the formation of a metastable P-NHC, an azomethine ylide, and a bicyclic phosphirane. 相似文献
4.
Despagnet-Ayoub E Solé S Gornitzka H Rozhenko AB Schoeller WW Bourissou D Bertrand G 《Journal of the American Chemical Society》2003,125(1):124-130
A broad range of (phosphino)(aryl)carbenes, 1b-d, 10a,b, and 14a,b, were prepared by photolysis of their diazo precursors. The influence of the steric and electronic properties of the aryl ring on the structure and stability of these carbenes was studied both experimentally and theoretically. Among the different stabilization modes investigated, those featuring an acceptor as well as a spectator aryl substituent result in stable or at least persistent carbenes that could be completely characterized by classical spectroscopic methods. In marked contrast, the new substitution pattern featuring a donor aryl ring results in a very fleeting carbene. 相似文献
5.
The potential energy surfaces for the chemical reactions of group 14 carbenes have been studied using density functional theory (B3LYP/LANL2DZ). Five boryl(phosphino)-based carbene (B-?-P) species, where ? = C, Si, Ge, Sn, and Pb, have been chosen as model reactants in this work. Also, four kinds of chemical reactions; intramolecular 1,2-migration, water insertion, alkene cycloaddition, and intermolecular dimerization, have been used to study the chemical reactivities of these group 14 carbenes. The present theoretical investigations suggest that the relative carbenic reactivity decreases in the order C > Si > Ge > Sn > Pb. That is, the heavier the group 14 atom (E), the more stable is the boryl(phosphino)-based B-?-P species towards chemical reactions. Our theoretical findings thus demonstrate that all boryl(phosphino)-based carbenes are isolable at room temperature because they are quite inert to chemical reactions, except that they are also moisture-sensitive molecules. Furthermore, the singlet-triplet energy splitting of the B-?-P, as described in the configuration mixing model attributed to the work of Pross and Shaik, can serve as a diagnostic tool for a better understanding and predicting of their chemical reactivities, kinetically and thermodynamically. The results obtained allow a number of predictions to be made. 相似文献
6.
Canac Y Conejero S Donnadieu B Schoeller WW Bertrand G 《Journal of the American Chemical Society》2005,127(20):7312-7313
(Amino)(silyl)carbenes, prepared by substitution reactions at a carbene center, can survive several days at 0 degrees C. These species are not push-pull carbenes as their phosphino analogues and therefore are excellent ligands for transition-metal centers. 相似文献
7.
Nathalie Merceron-Saffon Antoine Baceiredo 《Journal of organometallic chemistry》2004,689(8):1431-1435
Direct complexation of (amino)(phosphino)carbene 1a and (amino)(oxy)carbene 1b featuring a phosphino group in position-6 to the carbene with [Rh(CO)2Cl]2 has been studied. With the 1,2-bidentate ligand 1a, an original cationic complex 2 featuring two (amino)(phosphino)carbenes η2-bonded to the metal has been isolated in 79% yield. In the case of the 1,6-bidentate ligand 1b, a rhodium(I) complex 3 in which the carbene is in trans position relative to the CO ligand was obtained in 85% yield. Both compounds were fully characterized including X-ray diffraction studies. 相似文献
8.
Krysiak J Lyon C Baceiredo A Gornitzka H Mikolajczyk M Bertrand G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(8):1982-1986
The stability of phosphino(trimethylsilyl)carbenes bearing cyclic diamino substituents on phosphorus is strongly dependent on the steric hindrance of the nitrogen substituents. Phosphinocarbenes 3 and 7, derived from the trans-N,N'-diisopropylcyclohexane-1,2-diamine and N,N'-diisopropyl-1,2-ethanediamine, are not observed; instead the 1,3-diphosphete 4 and a novel six-membered heterocycle 8, which results from the dimerization of 3 and the reaction of 7 with its diazo precursor 6, respectively, have been isolated. In contrast, the phosphino(silyl)carbene 14 derived from N,N'-di-tert-butyl-1,2-ethanediamine has been isolated in high yield. By using the enantiomerically pure (S,S)-, and (R,R)-N,N'-di-tert-butyl-1,2-diphenyl-1,2-ethanediamines, the first optically pure phosphino(sily)carbenes (S,S)-17 and (R,R)-17 have been prepared. They react with methyl acrylate to give the corresponding cyclopropanes (S,S,R,R)-19 and (R,R,S,S)-19 with a total syn diastereoselectivity and an excellent enantioselectivity (de>98 %). 相似文献
9.
Martin D Illa O Baceiredo A Bertrand G Ortuño RM Branchadell V 《The Journal of organic chemistry》2005,70(14):5671-5677
[reaction: see text] The reactivity of phosphino(trimethylsilyl)carbenes 1 with several organic acids has been examined in order to evaluate the pKa values of the conjugate acids. Carbenes 1 react efficiently with C-organic acids such as 1,3-dimesitylimidazolium chloride, phenylacetylene, acetonitrile, and acetyltrimethylsilane, which have pKa's in DMSO in the range 18-31. However, the reaction of the conjugate acids 1H+ with the anion perturbs the determination of the genuine basicity of 1. Theoretical calculations have been performed in order to quantify the basicity of phosphino(trimethylsilyl)carbenes 1 and to compare them with that of N-heterocyclic carbenes 2. The pKa of 1H+ in DMSO has been computed to be in the 23.0-23.4 range, so that 1 is not strong enough as a base to spontaneously deprotonate organic acids such as phenylacetylene, acetonitrile, or acetyltrimethylsilane. However, its conjugate acid 1H+ is a strong electrophile and easily reacts with the nucleophilic conjugate bases of these acids leading to the formation of the corresponding phosphorus ylides. 相似文献
10.
Lecea B Ayerbe M Arrieta A Cossío FP Branchadell V Ortuño RM Baceiredo A 《The Journal of organic chemistry》2007,72(2):357-366
The mechanism and the origins of the stereocontrol observed in the reaction between differently substituted alkenes and stable (phosphino)(silyl)carbenes giving cyclopropanes have been studied computationally. These cyclopropanation reactions proceed via asynchronous concerted mechanisms involving early transition structures with a significant charge transfer from the carbene to the alkene moiety. The geometric features of these transition structures preclude a significant overlap between the orbitals required for secondary orbital interactions between the reactants. The stereoselectivity observed experimentally stems from favorable electrostatic and steric interactions between the reactants leading to the stereoisomers in which the phosphanyl and carbonyl or aryl groups are cis to each other. 相似文献
11.
Prof. Shabana Khan Prof. Dr. Herbert W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1636-1648
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. 相似文献
12.
《Angewandte Chemie (International ed. in English)》2017,56(34):10046-10068
Discovered in 2005, cyclic (alkyl)(amino)carbenes (CAACs) are among the most nucleophilic (σ donating) and also electrophilic (π‐accepting) stable carbenes known to date. These properties allow them to activate a variety of small molecules and enthalpically strong bonds, to stabilize highly reactive main‐group and transition‐metal diamagnetic and paramagnetic species, and to bind strongly to metal centers, which gives rise to very robust catalysts. The most important results published up to the end of 2013 are briefly summarized, while the majority of this Review focuses on findings reported within the last three years. 相似文献
13.
Cyclic (Amino)(aryl)carbenes (CAArCs) as Strong σ‐Donating and π‐Accepting Ligands for Transition Metals
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Bin Rao Huarong Tang Prof. Dr. Xiaoming Zeng Liu Liu Dr. Mohand Melaimi Prof. Dr. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2015,54(49):14915-14919
Cyclic (amino)(aryl)carbenes (CAArCs) result from the replacement of the alkyl substituent of cyclic (alkyl)(amino) carbenes (CAACs) by an aryl group. This structural modification leads to enhanced electrophilicity of the carbene center with retention of the high nucleophilicity of CAACs, and therefore CAArCs feature a small singlet–triplet gap. The isoindolium precursors are readily prepared in good yields, and deprotonation at low temperature, in the presence of [RhCl(cod)]2 and [(Me2S)AuCl] lead to air‐stable rhodium and gold CAArC‐supported complexes, respectively. The rhodium complexes promote the [3+2] cycloaddition of diphenylcyclopropenone with ethyl phenylpropiolate, and induce the addition of 2‐vinylpyridine to alkenes by CH activation. The gold complexes allow for the catalytic three‐component preparation of 1,2‐dihydroquinolines from aniline and phenyl acetylene. These preliminary results illustrate the potential of CAArC ligands in transition‐metal catalysis. 相似文献
14.
Kannan R Rahing V Cutler C Pandrapragada R Katti KK Kattumuri V Robertson JD Casteel SJ Jurisson S Smith C Boote E Katti KV 《Journal of the American Chemical Society》2006,128(35):11342-11343
Nanocompatible chemistry which utilizes a novel nontoxic phosphino amino acid as a reducing agent has resulted in the development of therapeutically useful gold nanoparticles under biologically benign media. Stabilization of gold nanoparticles by the edible gum arabic matrix has provided an effective pathway toward in vivo stable target-specific gold nanoparticles. 相似文献
15.
Synthesis and Reactivity of a CAAC–Aminoborylene Adduct: A Hetero‐Allene or an Organoboron Isoelectronic with Singlet Carbenes
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Fatme Dahcheh Dr. David Martin Prof. Dr. Douglas W. Stephan Prof. Dr. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2014,53(48):13159-13163
A one‐electron reduction of a cyclic (alkyl)(amino)carbene (CAAC)–bis(trimethylsilyl)aminodichloroborane adduct leads to a stable aminoboryl radical. A second one‐electron reduction gives rise to a CAAC–aminoborylene adduct, which features an allenic structure. However, in manner similar to that of stable electrophilic singlet carbenes, this compound activates small molecules, such as CO and H2. 相似文献
16.
Are Copper(I) Carbenes Capable Intermediates for Cyclopropanations? The Case for Ylide Intermediates
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Dr. Jamal T. Aldajaei Dr. James R. Keeffe Christopher A. Swift Dr. Scott Gronert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(36):12702-12708
A novel approach is used to synthesize a stable, ligated copper(I) carbene in the gas phase that is capable of typical metal carbenoid chemistry. However, it is shown that copper(I) carbenes generally undergo rapid unimolecular rearrangements including insertions into copper‐ligand bonds and Wolff rearrangements. The results indicate that most copper(I) carbenes are inherently unstable and would not be viable intermediates in condensed‐phase applications; an alternative intermediate that is less prone to rearrangements is required. Computational data suggest that ylides formed by the complexation of the carbene with solvent or other weak nucleophiles are viable intermediates in the reactions of copper(I) carbenes. 相似文献
17.
L3C3P3: Tricarbontriphosphide Tricyclic Radicals and Cations Stabilized by Cyclic (alkyl)(amino)carbenes
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Dr. Zhongshu Li Yuanfeng Hou Yaqi Li Dr. Alexander Hinz Prof. Dr. Jeffrey R. Harmer Prof. Dr. Cheng‐Yong Su Prof. Dr. Guy Bertrand Prof. Dr. Hansjörg Grützmacher 《Angewandte Chemie (International ed. in English)》2018,57(1):198-202
Alkynes usually oligomerize to give rings with a conjugated π‐electron system. In contrast, phosphaalkynes, R?C≡P, frequently give compounds with polycyclic structures, which are thermodynamically more stable than the corresponding π‐conjugated isomers. The syntheses of the first C3P3 tricyclic compounds are reported with either radical or cationic ground states stabilized by cyclic (alkyl)(amino)carbenes (CAACs). These compounds may be considered as examples of tricarbontriphosphide coordinated by carbenes and are likely formed via trimerization of the corresponding mono‐radicals CAAC‐CP.. The mechanism for the formation of these tricarbontriphosphide radicals has been rationalized by a combination of experiments and DFT calculations. 相似文献
18.
《Journal of organometallic chemistry》2005,690(24-25):5541-5545
Two original complexes featuring an (amino)(phosphino)carbene η2-bonded to the metal have been obtained in 60% and 80% yields, by addition of the corresponding stable carbene to PdCl2(cod) and NiCl2(PPh3)2, respectively. Both complexes have been fully characterized including X-ray diffraction studies. The catalytic activity of the palladium complex has been evaluated for aryl amination reactions. 相似文献
19.
A new two-dimensional classification of singlet carbenes based on the difference in reactivity of their insertion reactions into the C-H bonds of acetonitrile and isobutane is presented. This classification combines the stability and the philicity of divalent species. Until now all of the experimentally based philicity scales are based on the addition to alkenes. Moreover, a new terminology for describing the reactivity of carbenes is introduced. Among the alkyl carbenes, acetyl carbene (2) and cyclopentadienylidene are shown as highly reactive electrophilic carbenes, whereas the other alkylidenes and alkenylidenes investigated are all less active than 2 and more nucleophilic. The stabilized-nucleophilic bicyclo[2.1.1]hex-2-en-5-ylidene (13) possesses a stability similar to that of cyclic alkyl amino carbene (CAAC) 18 and aminophosphoniocarbene 7. Strong hydrogen bridging is found between a C-H bond of acetonitrile and the nucleophilic carbenes 13 and 14. 相似文献
20.
WANG Jun-Wen XU Fang-Bo LI Qiang-Shan SONG Hai-Bin LIU Yong-Sheng ZHANG Zheng-Zhi 《有机化学》2004,24(Z1):213
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). 相似文献