共查询到20条相似文献,搜索用时 15 毫秒
1.
Becker E Stingl V Dazinger G Puchberger M Mereiter K Kirchner K 《Journal of the American Chemical Society》2006,128(20):6572-6573
The reaction of [RuCp(IPri)(CH3CN)2]PF6 (IPri = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with HCCR (R = COOMe, COOEt, COMe) yields the allyl carbene complexes [RuCp(=C(R)-eta3-CHC(R)CH-IPri)]PF6. This conversion involves selective head-to-tail coupling of two alkynes and an unusual migratory insertion of the N-heterocyclic carbene into the ruthenium-carbon double bond of a ruthenacyclopentatriene intermediate. 相似文献
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William J. Ramsay Jonathan A. Foster Katharine L. Moore Tanya K. Ronson Rapha?l J. Mirgalet David A. Jefferson Jonathan R. Nitschke 《Chemical science》2015,6(12):7326-7331
The incorporation of an N-heterocyclic carbene (NHC) moiety into a self-assembled MII4L6 cage framework required the NHC first to be metallated with gold(i). Bimetallic cages could then be constructed using zinc(ii) and cadmium(ii) templates, showing weak luminescence. The cages were destroyed by the addition of further gold(i) in the form of AuI(2,4,6-trimethoxybenzonitrile)2SbF6, which caused the reversibly-formed cages to disassemble and controllably release the AuI-NHC subcomponent into solution. This release in turn induced the growth of gold nanoparticles. The rate of dianiline release could be tuned by capsule design or through the addition of chemical stimuli, with different release profiles giving rise to different nanoparticle morphologies. 相似文献
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We report the first asymmetric sulfa-Michael addition (SMA) reactions using a chiral N-heterocyclic carbene (NHC) as a non-covalent organocatalyst. We demonstrate that a triazolium salt derived NHC functions as an excellent Brønsted base to promote enantioselective carbon–sulfur bond formation. The reaction is applicable to a wide range of thiols and electrophilic olefins. Notably, quaternary chiral centers bearing both an S atom and a CF3 group were synthesized with excellent asymmetric control. Mechanistic studies suggest that the facial discrimination is likely to be guided by non-covalent interactions: hydrogen bonding and π–π stacking. 相似文献
5.
Takaki D Okayama T Shuto H Matsumoto S Yamaguchi Y Matsumoto S 《Dalton transactions (Cambridge, England : 2003)》2011,40(7):1445-1447
Indenyl-functionalised BEt(3)-adduct NHCs were prepared by the reaction of imidazolium pro-ligands with LiBEt(3)H. This compound was converted into the indenyl-coordinate molybdenum complex dangling the NHC·BEt(3) moiety as a substituent. The stepwise coordination of NHC afforded a chelate-type mononuclear complex as well as a bimetallic complex. 相似文献
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Lefebvre JF Lo M Leclercq D Richeter S 《Chemical communications (Cambridge, England)》2011,47(10):2976-2978
NHC ligands annulated to free-base porphyrins can be reversibly switched between electron-poor and electron-rich states upon protonation and deprotonation of the inner nitrogen atoms of the porphyrin. Metallation of the macrocycle with nickel(II) locks the peripheral NHC ligand in its electron-rich state. 相似文献
7.
Dutton JL Tuononen HM Jennings MC Ragogna PJ 《Journal of the American Chemical Society》2006,128(39):12624-12625
The room-temperature reaction between the Dipp2DAB ligand, SnCl2, and SeCl4 results in the quantitative formation of a dicationic N-heterocyclic "carbenoid". This represents the first example of a chalcogenium dication that mimics the ubiquitous Arduengo-type carbenes; however, the electronic structure is significantly different. 相似文献
8.
Adam F. Henwood Mathieu Lesieur Ashu K. Bansal Vincent Lemaur David Beljonne David G. Thompson Duncan Graham Alexandra M. Z. Slawin Ifor D. W. Samuel Catherine S. J. Cazin Eli Zysman-Colman 《Chemical science》2015,6(5):3248-3261
We report the first examples of highly luminescent di-coordinated Pd(0) complexes. Five complexes of the form [Pd(L)(L′)] were synthesized, where L = IPr, SIPr or IPr* NHC ligands and L′ = PCy3, or IPr and SIPr NHC ligands. The photophysical properties of these complexes were determined in degassed toluene solution and in the solid state and contrasted to the poorly luminescent reference complex [Pd(IPr)(PPh3)]. Organic light-emitting diodes were successfully fabricated but attained external quantum efficiencies of between 0.3 and 0.7%. 相似文献
9.
Suzuki reactions of aryl chlorides and arylboronic acids with a range of electronically different N-heterocyclic carbene ligands derived from N,N-diadamantylbenzimidazolium salts are reported. Results indicate that an electron-rich NHC ligand enhances the rate of oxidative addition. However, reductive elimination is unchanged by the electronic nature of the supporting ligand and is primarily affected by the steric environment. 相似文献
10.
Sébastien G. Guillet Dr. Ishfaq Ibni Hashim Marek Beliš Prof. Dr. Kristof Van Hecke Prof. Dr. Catherine S. J. Cazin Prof. Dr. Steven. P. Nolan 《欧洲无机化学杂志》2023,26(24):e202300327
A simple synthetic method to access a wide range of [Rh(acac)(CO)(NHC)] complexes is described. In situ infra-red monitoring provides insights into the mechanism of the reaction, including the identification of a key intermediate. An understanding of the reaction mechanism leads to the discovery of novel pathways to commonly used congeners. 相似文献
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We describe a stepwise synthesis of the hydrido, N-heterocyclic dicarbene iridium(III) pincer complex [Ir(H)I(C(NHC)CC(aNHC))(NCMe)] (3) which features a combination of normal and abnormal NHC ligands. The reaction of the bis(imidazolium) diiodide [(CH(imid)CHCH(imid))]I(2) (1) with [Ir(μ-Cl)(cod)](2) afforded first the mono-NHC Ir(I) complex [IrI(cod)(CH(imid)CHC(NHC))]I (2), which was then reacted with 2 equiv. of Cs(2)CO(3) in acetonitrile at 60 °C for 40 h to yield 3. These observations support our previously proposed mechanism for the formation of hydrido, N-heterocyclic dicarbene iridium(III) pincer complexes from the reaction of bis(imidazolium) salts with weak bases involving a mono-NHC Ir(I) intermediate. We describe the reactivity of the mono-NHC Ir(I) complex 2 under various conditions. By changing the reaction solvent from MeCN to toluene, we observed the cleavage of the imidazol-2-ylidene ring and the formation of an iminoformamide-containing mono-NHC Ir(I) complex [IrI(cod){[NHCH=CHN(Ad)CHO]CHC(NHC)}] (4). Complex 4 was also prepared in high yield from the reaction of 2 with strong bases (potassium tert-butoxide or potassium hexamethyldisilazane), via the initial formation of the complex [IrI(cod)(CH(NHC)CHC(NHC))] (5), which contains a coordinated NHC moiety and a free carbene arm, followed by subsequent hydrolysis of the latter. The bis(imidazolium) salt 1 can be deprotonated by strong bases to form the bis(carbene) ligand C(NHC)CHC(NHC) (6), which readily reacts with [Ir(μ-Cl)(cod)](2) to give the dinuclear complex [{IrI(cod)}(2)(μ-C(NHC)CHC(NHC))] (7), in which the N-heterocyclic bis(carbene) ligand bridges the two metals through the carbene carbon atoms. 相似文献
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A series of structurally diverse gold and silver complexes extending from ionic (NHC) 2M(+)Cl(-) (M=Au, Ag) type complexes to large 12-membered macrometallacycles have been prepared by the appropriate modification of the N-substituent of amido-functionalized N-heterocyclic carbenes. Specifically, the ionic, [1-(R)-3-{ N-(t-butylacetamido)imidazol-2-ylidene}]2M(+)Cl(-), (R=t-Bu, i-Pr; M=Au, Ag; 1b, 1c, 2b, 2c) complexes, were obtained in case of the N- t-butyl substituent of the amido-functionalized sidearm while 12-membered macrometallacycles, [1-(R)-3-{N-(2,6-di i-propylphenylacetamido)imidazol-2-ylidene}]2M2, (R=t-Bu, i-Pr; M=Au, Ag; 3b, 3c, 4b, 4c) were obtained in case of the 2,6-di i-propylphenyl N-substituent. These structurally diverse complexes of gold and silver were, however, prepared employing a common synthetic pathway involving the reactions of the imidazolium chloride salts (1a, 2a, 3a, 4a) with Ag2O to give the silver complexes (1b, 2b, 3b, 4b) and which, when treated with (SMe2)AuCl, gave the gold complexes (1c, 2c, 3c, 4c). Detailed density functional theory studies of 1b, 1c, 2b, 2c, 3b, 3c, 4b, and 4c were carried out to gain insight about the structure, bonding, and the electronic properties of these complexes. The NHC-metal interaction in the ionic 1b, 1c, 2b, and 2c complexes is primarily composed of the interaction of the carbene lone pair with the empty p orbital of the metal (5p for Ag and 6p for Au) while the same in the macrometallacyclic 3b, 3c, 4b, and 4c complexes consisted of the interaction of the carbene lone pair with the empty s orbital of the metal (5s for Ag and 6s for Au). The observation of a low energy emission in about the 580-650 nm region has been tentatively assigned to originate from the presence of weak metallophilic interaction in these macrometallacyclic 3b, 3c, 4b, and 4c complexes. 相似文献
14.
Tatsuya Uchida 《Tetrahedron letters》2009,50(33):4741-9446
We synthesized in three steps simple chiral bidentate NHC compounds that carry an achiral coordinating group as N-substituent and revealed that they serve as efficient chiral auxiliaries for the copper-catalyzed asymmetric conjugate addition of dialkylzinc to acyclic enones (up to 97% ee). 相似文献
15.
Galan BR Gembicky M Dominiak PM Keister JB Diver ST 《Journal of the American Chemical Society》2005,127(45):15702-15703
In the presence of carbon monoxide, ruthenium carbenes give a net insertion/ring expansion (Buchner reaction) into one of the aromatic rings of the N-heterocyclic carbene ligand. In alkene metathesis applications, the N-heterocyclic carbene ligand is both robust and typically inert to reactions with the metal-bound carbene. This unique reaction is completely regioselective. The complexes obtained through ring expansion were fully characterized in the solid state using X-ray crystallography and in solution using NMR and IR spectroscopy. 相似文献
16.
Takao Noguchi Bappaditya Roy Daisuke Yoshihara Youichi Tsuchiya Tatsuhiro Yamamoto Seiji Shinkai 《Chemical science》2015,6(7):3863-3867
This study demonstrates how to control the selectivity and the turn-on detection range toward the tailoring of an assembly-based fluorescence (FL) sensory system. Assembly-based FL chemosensors composed of oligophenylenevinylene with a varied number of guanidinium receptors (G2, G4 and G6) were newly developed, and their FL response to nucleotides (AMP, ADP and ATP) was investigated. Indeed, G6 exhibited FL emission via self-assembly with ATP. More importantly, the FL response of G6 showed markedly improved selectivity for ATP over ADP and a broadly extended detection range of ATP concentration under adjusted salt conditions. The salt effect on the FL response revealed the competitive binding interactions affecting the subsequent self-assembly process. These studies have unveiled the pivotal binding mechanisms operating in the self-assembly process, which tailor the performance level of the assembly-based sensory system. We believe that this study offers a new design principle of an assembly-based FL chemosensor with high selectivity and the appropriate detection range, being different from the conventional key-and-lock system. 相似文献
17.
Ratiometric detection of pH fluctuation in mitochondria with a new fluorescein/cyanine hybrid sensor
Yuncong Chen Chengcheng Zhu Jiajie Cen Yang Bai Weijiang He Zijian Guo 《Chemical science》2015,6(5):3187-3194
The homeostasis of mitochondrial pH (pHm) is crucial in cell physiology. Developing small-molecular fluorescent sensors for the ratiometric detection of pHm fluctuation is highly demanded yet challenging. A ratiometric pH sensor, Mito-pH, was constructed by integrating a pH-sensitive FITC fluorophore with a pH-insensitive hemicyanine group. The hemicyanine group also acts as the mitochondria targeting group due to its lipophilic cationic nature. Besides its ability to target mitochondria, this sensor provides two ratiometric pH sensing modes, the dual excitation/dual emission mode (Dex/Dem) and dual excitation (Dex) mode, and its linear and reversible ratiometric response range from pH 6.15 to 8.38 makes this sensor suitable for the practical tracking of pHm fluctuation in live cells. With this sensor, stimulated pHm fluctuation has been successfully tracked in a ratiometric manner via both fluorescence imaging and flow cytometry. 相似文献
18.
Three half-sandwichruthenium(II) complexes with pyridine/phenylene bridged NHC = E (NHC = N-heterocyclic carbene, E = S, Se) ligands [Ru(p-cymene)L](PF6)1–2 ( 1a–1c , L = ligand) were synthesized and characterized. All ruthenium complexes were fully characterized by 1H and 13C NMR spectra, mass spectrometry, and single-crystalX-ray diffraction methods. Moreover, the half-sandwich ruthenium complexes with NHC = E ligands showed highly catalytic activities towards to the tandem dehydrogenation of ammonia borane (AB) and hydrogenation of R–NO2 to R–NH2 at 353 K in water. 相似文献
19.
Sarah A. Shepherd Chinnan Karthikeyan Jonathan Latham Anna-Winona Struck Mark L. Thompson Binuraj R. K. Menon Matthew Q. Styles Colin Levy David Leys Jason Micklefield 《Chemical science》2015,6(6):3454-3460
Flavin-dependent halogenases are potentially valuable biocatalysts for the regioselective halogenation of aromatic compounds. These enzymes, utilising benign inorganic halides, offer potential advantages over traditional non-enzymatic halogenation chemistry that often lacks regiocontrol and requires deleterious reagents. Here we extend the biocatalytic repertoire of the tryptophan halogenases, demonstrating how these enzymes can halogenate a range of alternative aryl substrates. Using structure guided mutagenesis we also show that it is possible to alter the regioselectivity as well as increase the activity of the halogenases with non-native substrates including anthranilic acid; an important intermediate in the synthesis and biosynthesis of pharmaceuticals and other valuable products. 相似文献
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Ulrich J. Scheele 《Tetrahedron letters》2007,48(47):8366-8370
One or two imidazolium groups have been attached to the 3- and 6-positions of the pyridazine heterocycle, providing valuable precursors for mono- and binucleating NHC/pyridazine hybrid ligands. For N-methyl imidazole with specific backbone substituents an unexpected methyl group transfer is observed, which defines the scope of the synthetic procedure. H-Bonding patterns in the solid state are elucidated by X-ray crystallography for seven chloride or salts of the new compounds. 相似文献