共查询到20条相似文献,搜索用时 15 毫秒
1.
Anja C Frisch 《Journal of organometallic chemistry》2003,687(2):403-409
For the first time it is shown that N-heterocyclic carbenes are suitable ligands for the palladium-catalyzed coupling of alkyl chlorides with aryl Grignard reagents. A variety of simple as well as functionalized primary alkyl chlorides provide the corresponding alkyl benzenes in general in good to very good yield. By comparing the 1,3-dimesitylimidazol-2-ylidene (IMes) palladium(0) naphthoquinone complex with the previously known palladium phosphine catalyst for the model coupling reaction of 1-chlorohexane with phenylmagnesium bromide it is demonstrated that the new catalyst system is superior. 相似文献
2.
Z.K. Yu F.L. Zeng H.X. Deng J.H. Dong H.M. Wang 《Journal of organometallic chemistry》2007,692(11):2306-2313
Complex RuCl2(PPh3)(iBu-BTP) (5) was synthesized by the reaction of 2,6-bis(5,6-bis(iso-butyl)-1,2,4-triazin-3-yl)pyridine (iBu-BTP) and RuCl2(PPh3)3 in refluxing toluene, and its molecular structure was confirmed by X-ray crystallographic determination. Complex 5 was applied as a catalyst for transfer hydrogenation of ketones and exhibited catalytic activity comparable to RuCl2(PPh3)(Me4BPPy) (1) (Me4BPPy = bis(3,5-dimethylpyrazol-1-yl)pyridine) in some cases. The difference between the catalytic activity of 5 and 1 is attributed to the significantly different arrangement and positions of the PPh3 and chlorides and also to the different electron density on the N-heterocycles. Complex 1 exhibited good to excellent catalytic activity in hydrogenation of ketones under mild conditions. These results have suggested new applications of iBu-BTP and Me4BPPy as promising planar tridentate pseudo-N3 ligands to construct highly active transition-metal catalysts. 相似文献
3.
Elena Mas-Marzá Eduardo Peris Beatriz Royo 《Journal of organometallic chemistry》2006,691(12):2708-2712
Compound MoO2Cl2(THF)2 reacts with two equivalents of 1,3-dialkyl substituted 4,5-dimethylimidazol-2-ylidenes to give the dioxomolybdenum(VI) complexes MoO2Cl2(LR)2 [R = Me (1), i-Pr (2)]. Treatment of MoO2Cl2(THF)2 with one equivalent of the N-heterocyclic carbenes LMe, Li-Pr and C1Ln-Bu (LMe = 1,3,4,5-tetramethylimidazol-2-ylidene, Li-Pr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, and C1Ln-Bu = 1,3-dibutyl-4,5-dichloroimidazol-2-ylidene) affords the monocarbene adducts MoO2Cl2(LR) [R = Me (3), i-Pr (4)] and MoO2Cl2(C1Ln-Bu) (5), respectively. Decomposition of complexes 1-5 affords a molybdenum oxychloride anion [Mo2O5Cl4]2− as an imidazolium salt. 相似文献
4.
The preparation and properties of mono- versus bis(carbene) Pd(II) complexes bearing unsymmetrical cyano- and ester-functionalized NHC ligands as potential IR probes were studied in detail. Direct reaction of Pd(OAc)2 with functionalized imidazolium salts afforded either bis(carbene) (3a, c) or monocarbene complexes (5, 6) with a N-coordinated imidazole co-ligand. The latter were exclusively obtained with N-ethylene substituted salts, which were found to undergo N-C cleavage reaction. The milder Ag-carbene transfer reaction on the other hand was tolerable to the length of the substituents and the nature of the functional groups. All bis(carbene) complexes (3a-c, 4a-c) were obtained as a inseparable mixture of square-planar trans-anti and trans-syn rotamers. The identity, ratio and dynamic equilibrium of these rotamers have been investigated and the relatively high rotational barrier for rotamers of 3a was estimated to be about 74 kJ mol−1 at 380 K. All eight complexes were fully characterized by NMR and IR spectroscopies, ESI mass spectrometry and X-ray single crystal and powder diffraction. A preliminary catalytic study showed that ester-functionalized complexes 4a and 4b gave rise to highly active catalyst in the double Mizoroki-Heck coupling of aryl dibromides, while the in situ ester-hydrolyzed complexes were also active in the coupling of activated aryl chlorides. 相似文献
5.
David E. Bergbreiter Haw-Lih Su Hisao Koizumi Jianhua Tian 《Journal of organometallic chemistry》2011,696(6):1272-6917
This paper describes how the nonpolar polymer polyisobutylene (PIB) can be used as a handle to prepare PIB-bound NHC ligands that are soluble in monophasic mixtures of mixed solvents but phase separable when such solvent systems are perturbed to be biphasic. The results here show that such PIB-bound NHC ligands can be used to synthesize useful palladium catalysts. In this paper, both PIB-bound analogs of an N,N′-bis(2,6-diisopropylphenyl) heterocyclic carbene and simpler N,N′-dialkyl heterocyclic carbene ligand were prepared and were successfully used to form palladium cross-coupling catalysts. The reactivity, recycling and reusability of these catalysts has been examined. 相似文献
6.
Hon Man Lee Chi Ying Lu Chih Yuan Chen Wen Ling Chen Hung Ching Lin Pei Ling Chiu Pi Yun Cheng 《Tetrahedron》2004,60(27):5807-5825
A series of new ethylene-bridged bis(imidazolium) halides with various N-substitutions were synthesized. Complexation of these imidazolium halides with Pd(OAc)2 produced new Pd(II) ethylene-bridged bis(carbene) complexes. Crystallographic analyses of some of the new imidazolium salts and Pd(II) complexes were determined. Applications of these seven-member palladacycles in Suzuki and Heck coupling reactions produced comparable catalytic activities to those of six-member analogs. 相似文献
7.
Agnieszka Hryniewicka Iwona Misztalewska Dorota Czajkowska-Szczykowska Zofia Urbańczyk-Lipkowska Jacek W. Morzycki Stanisław Witkowski 《Tetrahedron》2014
Synthesis of new type of the Hoveyda–Grubbs catalysts containing modified N-heterocyclic carbene ligands is described herein. New catalysts bear different in size polyether clamp embracing N,N′-2,4-dimethylphenyl substituents in N-heterocyclic carbene. New complexes were tested in model RCM, enyne and CM reactions. They showed comparable activity to that of commercially available Grubbs second generation and Hoveyda–Grubbs second generation complexes. Complex with larger polyether clamp proved Z-stereoselective in a macrocycle formation and yielded more Z isomers than commercial complexes in CM reactions. The catalysts are stable and easy to purify. 相似文献
8.
Rosenani A. Haque Abbas Washeel Salman Teoh Siang Guan Hassan Hadi Abdallah 《Journal of organometallic chemistry》2011,696(22):3507-3512
Mononuclear mercury complexes (1, 2, and 3) bearing bis-N-heterocyclic carbene (NHC) ligands of the form [(NHC)2-μ-Hg]+2 have been prepared and structurally characterised. The complexes were derived from three bis-imidazolium salts as precursors to NHC; either 1,3-bis(N-methylimidazolium-1-ylmethyl)benzene bis(hexafluorophosphate) (I·2PF6), 1,3-bis(N-butylimidazolium-1-ylmethyl)benzene bis(hexafluorophosphate) (II·2PF6) or 3,5-bis(N-butylimidazolium-1-ylmethyl)toluene bis(hexafluorophosphate) (III·2PF6) treated with mercury(II) acetate. Interestingly X-ray crystal structure analysis revealed a close interaction between the Hg metal centre with one carbon atom of the aryl linker in addition to coordination with two NHCs. 相似文献
9.
Jang-Woong Byun 《Tetrahedron letters》2004,45(9):1837-1840
A novel polymer-supported N-heterocyclic carbene (NHC) was prepared from chloromethyl polystyrene (CM PS) resin using a simple procedure, and was used as the ligand for palladium (Pd) catalysts. The polymer-supported Pd-NHC complexes efficiently catalyzed the Suzuki cross-coupling of aryl halides and phenylboronic acid in good yields and excellent purities under aqueous conditions. 相似文献
10.
A new class of hemilabile unsymmetrical 2-(1-arylimino)-6-(pyzazol-1-yl)pyridine ligands and their ruthenium(II) and nickel(II) NNN complexes were synthesized. The Ru(II) complex catalysts have been fully characterized and exhibited good to excellent catalytic activity in the transfer hydrogenation (TH) of ketones in refluxing 2-propanol. These results have demonstrated rare examples of active ruthenium(II) NNN complex catalysts that do not feature a N-H functionality for TH of ketones. 相似文献
11.
New bis(NHC)-Pd complexes were synthesized and characterized by elemental analysis, 1H NMR, 13C NMR, and IR spectroscopy. The reaction of Pd(OAc)2 and bis(benzimidazolium) salts in DMSO gave the monomeric palladium complex in which the N-heterocyclic carbene was bound to the metal centre. The crystal and molecular structure of the cis-dibromo{1,1′-di[2,3,4,5,6-pentamethylbenzyl]-3,3′-butylenedibenzimidazol-2,2′-diylidene}-palladium(II) complex was determined by single-crystal X-ray diffraction. The activity of the Pd(II) complexes in the direct arylation of benzothiazole with arylbromides was investigated. A preliminary catalytic study showed that these bis(NHC)-Pd complexes were highly active in the direct arylation of benzothiazole with arylbromides. 相似文献
12.
Yuan Han 《Journal of organometallic chemistry》2008,693(19):3159-3165
Reaction of the sterically bulky 1,3-dibenzhydrylbenzimidazolium bromide (Bh2-bimyH+Br−) (A) with Pd(OAc)2 in DMSO yielded a mono(carbene) Pd(II) complex 1 with a N-bound benzimidazole derivative, which resulted from an unusual NHC rearrangement reaction. Reaction of A with Ag2O, on the other hand, cleanly gave the Ag(I) carbene complex [AgBr(Bh2-bimy)] (2), which has been used as a carbene-transfer agent to prepare the acetonitrile complex trans-[PdBr2(CH3CN)(Bh2-bimy)] (3). Dissociation of acetonitrile from complex 3 and subsequent dimerization afforded the dinuclear Pd(II) complex [PdBr2(Bh2-bimy)]2 (4) in quantitative yield. All complexes were fully characterized by multinuclear NMR spectroscopies, ESI mass spectrometry and X-ray diffraction analysis. Furthermore, the catalytic activity of complex 4 in aqueous Suzuki-Miyaura cross-coupling reactions was studied and compared with that of its previously reported less bulky analogue [PdBr2(iPr2-bimy)]2. 相似文献
13.
Hongping Ren 《Journal of organometallic chemistry》2006,691(19):4109-4113
A series of cyclopentadienyl N-heterocyclic carbene copper complexes CpCu(NHC) were synthesized and structurally characterized. The effect of the substituents at the nitrogen atom of the NHC ligands on the structures and thermally stability was discussed. 相似文献
14.
New tetraimidazolinium and tetrabenzimidazolium salts have been prepared. Upon reaction with tBuOK, they generate carbene ligands, which were associated in situ to [RuCp*(MeCN)3]PF6 to produce new ruthenium catalysts that are active for the substitution of allylic substrates by amines, phenols, and carbonucleophiles. The influence of the N-heterocyclic core as well as that of the N-substitutents at the periphery of the salts, on reactivity and regioselectivity have been examined. 相似文献
15.
Sterically hindered salicylaldimine functionalized imidazolium salts 2 have been prepared. The structures of the synthesized compounds were determined by spectroscopic techniques. The reaction of these salts containing arylmethyl-N chain (aryl: phenyl (2a), 2,4,6-trimethylphenyl (2b), 2,3,4,5,6-pentamethylphenyl (2c)) with Pd(OAc)2 in boiling toluene afforded Pd(II) complexes 3 in high yields. The X-ray structure of 1-[3-(3,5-di-tert-butyl-2-oxophenyl)propyliminato]-3-(2,4,6-trimethylbenzyl)imidazol-2-ylidenebromopalladium(II) (3b) has been determined. The Suzuki-Miyaura reaction was used to investigate their activity as catalysts either prepared in situ or from well-defined complexes. They are efficient when activated arylbromides are used as substrates. 相似文献
16.
A series of α-keto esters and α,α,α-trifluoromethyl ketones were reduced in high yields and excellent enantioselectivities under Ru-catalysed transfer hydrogenation using novel chiral N-arenesulfonyl-1,2-diphenylethylenediamine ligands. 相似文献
17.
Taichi Kano 《Tetrahedron letters》2006,47(27):4615-4618
The synthetic utility of N-heterocyclic carbenes was demonstrated by the trialkylsilylcyanation of aldehydes, ketones and imines. In the presence of a catalytic amount of 3a, the reactions with Me3SiCN proceeded smoothly to give the corresponding cyanohydrin trimethylsilyl ethers or amino nitrile derivatives in good to excellent yields. 相似文献
18.
Hongping Ren 《Journal of organometallic chemistry》2007,692(10):2092-2098
A facile synthesis of o-hydroxyaryl-substituted N-heterocyclic carbene ligands and their complexes with palladium is presented. This kind of salicylaldimine-like NHC ligands expands the class of available NHC ligands for organometallic catalysts. 相似文献
19.
A simple N-acylimidazolium salt precursor to a NHC-complexed palladacyclic ligand gives high turnover numbers (>107) for Suzuki-Miyaura coupling and is applied to the preparation of biaryls used in the synthesis of coumarins. The results suggest that N-acyl-NHC derivatives can contribute to further expanding the rich chemistry of NHCs. 相似文献
20.
Asymmetric hydrogenation of ketones (AHK) was revolutionized in 1987 and again in 1995 when Ru(CH3COO)2(binap)/HCl and RuCl2(binap)/diamine, respectively, were developed. Since then, the number of reports on Ru-catalyzed AHK has increased exponentially, and the utility of other precious metals (Os, Rh, Ir, and Pd) has also been shown. The utilization of inexpensive base metals (Fe, Co, Ni, and Cu) has been a recent trend. This digest summarizes the key advances in AHK in the past decade by categorizing the chiral ligands into six types: (i) diphosphines, (ii) diphosphines/diamines, (iii) tridentate or tetradentate phosphine amines, (iv) diamines, (v) tetradentate amines, and (vi) tetradentate thioether amines. 相似文献