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Автор: Grafiati
Опубліковано: 8 червня 2024

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1

Alauddin, Mohammad, and Mazharul M. Islam. "A computational characterization of N-heterocyclic carbenes for catalytic and nonlinear optical applications." Zeitschrift für Naturforschung B 79, no. 4 (April 1, 2024): 215–23. http://dx.doi.org/10.1515/znb-2023-0092.

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Abstract Very recently, N-heterocyclic carbenes (NHCs) have found a wide range of applications in the fields of catalysis and nonlinear optics. Herein, we have employed 1,3-bis-(1(S)-benzyl)-4,5-dihydro-imidazol-based carbene as a reference molecule and substituted one H atom from each CH2 of the benzyl groups in both sides by CH3, NH2, and CF3 to study the thermodynamic and opto-electronic properties of NHCs theoretically. It was observed that the enthalpy (H), Gibb’s free energy (G), specific heat capacity (C v), and entropy (S) increase significantly in the presence of the electron-withdrawing groups compared to the electron-donating groups. The IR active in-plane bending vibrations of the CH (NHC) group are shifted to the higher frequency region for the considered substituted molecules compared to the reference carbene. The analysis of the electronic properties shows that the CH3-substituted carbene is more reactive for catalytic activities compared to other NHCs. The calculated nonlinear optical (NLO) properties reveal that the NH2-substituted NHC has the largest hyperpolarizability value whereas the CH3-substituted NHC has the largest dipole moment and polarizability among all, making them potential candidates for the development of NLO materials.
2

Mokfi, Moloud, Jörg Rust, Christian W. Lehmann, and Fabian Mohr. "Facile N9-Alkylation of Xanthine Derivatives and Their Use as Precursors for N-Heterocyclic Carbene Complexes." Molecules 26, no. 12 (June 17, 2021): 3705. http://dx.doi.org/10.3390/molecules26123705.

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The xanthine-derivatives 1,3,7-trimethylxanthine, 1,3-dimethyl-7-benzylxanthine and 1,3-dimethyl-7-(4-chlorobenzyl)xanthine are readily ethylated at N9 using the cheap alkylating agents ethyl tosylate or diethyl sulfate. The resulting xanthinium tosylate or ethyl sulfate salts can be converted into the corresponding PF6- and chloride salts. The reaction of these xanthinium salts with silver(I) oxide results in the formation of different silver(I) carbene-complexes. In the presence of ammonia, ammine complexes [Ag(NHC)(NH3)]PF6 are formed, whilst with Et2NH, the bis(carbene) salts [Ag(NHC)2]PF6 were isolated. Using the xanthinium chloride salts neutral silver(I) carbenes [Ag(NHC)Cl] were prepared. These silver complexes were used in a variety of transmetallation reactions to give the corresponding gold(I), ruthenium(II) as well as rhodium(I) and rhodium(III) complexes. The compounds were characterized by various spectroscopic methods as well as X-ray diffraction.
3

Longevial, Jean-François, Mamadou Lo, Aurélien Lebrun, Danielle Laurencin, Sébastien Clément, and Sébastien Richeter. "Molecular complexes and main-chain organometallic polymers based on Janus bis(carbenes) fused to metalloporphyrins." Dalton Transactions 49, no. 21 (2020): 7005–14. http://dx.doi.org/10.1039/d0dt00594k.

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Janus bis(N-heterocyclic carbenes) composed of a porphyrin core with two N-heterocyclic carbene (NHC) heads fused to opposite pyrroles were used as bridging ligands for the preparation of metal complexes.
4

Jutand, Anny, Julien Pytkowicz, Sylvain Roland, and Pierre Mangeney. "Mechanism of the oxidative addition of aryl halides to bis-carbene palladium(0) complexes." Pure and Applied Chemistry 82, no. 7 (May 4, 2010): 1393–402. http://dx.doi.org/10.1351/pac-con-09-09-22.

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Bis-N-heterocyclic carbenes Pd0 complexes, Pd0(NHC)2, are efficient catalysts in Heck reactions performed with aryl bromides or chlorides. The Pd0(NHC)2 that are not stable are generated in situ from PdII precursors PdY2(NHC)2 (Y = halides) after a chemical reduction. The latter procedure can be mimicked by an electrochemical reduction. The transient Pd0(NHCBn)2 is generated by electrochemical reduction of PdY2(NHCBn)2, and its reactivity in oxidative addition to aryl bromides and chlorides is characterized by the same electrochemical technique with the determination of the rate constants. Pd0(NHCBn)2 is found to be more reactive than the mixed complex Pd0(NHCBn)(PPh3). Both are the reactive species in an associative mechanism. Comparison with the isolated Pd0(NHCtBu)2 reveals that Pd0(NHCBn)2 is more reactive than Pd0(NHCtBu)2 even if the latter reacts via the mono-carbene Pd0(NHCtBu) in a dissociative mechanism. This suggests that the formation of mono-carbene Pd0(NHC) is not a guarantee for a fast oxidative addition because it is always generated at low concentration in its equilibrium with the related nonreactive bis-carbene Pd0(NHC)2.
5

Nonnenmacher, Michael, Dominik M. Buck, and Doris Kunz. "Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes." Beilstein Journal of Organic Chemistry 12 (August 23, 2016): 1884–96. http://dx.doi.org/10.3762/bjoc.12.178.

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Rh(CO)2Cl(NHC) complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C–H coupling constant of the respective imidazolium salts and the N–C–N angle of the N-heterocyclic carbene (NHC), a weaker σ-donor character than that of typical unsaturated NHCs is expected. However, the IR stretching frequencies of their Rh(CO)2Cl complexes suggest an electron-donor character even stronger than that of saturated NHCs. We ascribe this to the extremely weak π-acceptor character of the dipyrido-annelated NHCs caused by the conjugated 14 πe− system that thus allows for an enhanced Rh–CO backbonding. This extremely low π-acceptor ability is also corroborated by the 77Se NMR chemical shift of −55.8 ppm for the respective selenourea, the lowest value ever measured for imidazole derived selenoureas. DFT-calculations of the free carbene confirm the low σ-donor character by the fact that the σ-orbital of the carbene is the HOMO−1 that lies 0.58 eV below the HOMO which is located at the π-system. Natural population analysis reveals the lowest occupation of the pπ-orbital for the saturated carbene carbon atom and the highest for the pyrido-annelated carbene. Going from the free carbene to the Rh(CO)2Cl(NHC) complexes, the increase in occupancy of the complete π-system of the carbene ligand upon coordination is lowest for the pyrido-annelated carbene and highest for the saturated carbene.
6

Qie, Boyu, Ziyi Wang, Jingwei Jiang, Zisheng Zhang, Peter H. Jacobse, Jiaming Lu, Xinheng Li, et al. "Synthesis and characterization of low-dimensional N-heterocyclic carbene lattices." Science 384, no. 6698 (May 24, 2024): 895–901. http://dx.doi.org/10.1126/science.adm9814.

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The covalent interaction of N-heterocyclic carbenes (NHCs) with transition metal atoms gives rise to distinctive frontier molecular orbitals (FMOs). These emergent electronic states have spurred the widespread adoption of NHC ligands in chemical catalysis and functional materials. Although formation of carbene-metal complexes in self-assembled monolayers on surfaces has been explored, design and electronic structure characterization of extended low-dimensional NHC-metal lattices remains elusive. Here we demonstrate a modular approach to engineering one-dimensional (1D) metal-organic chains and two-dimensional (2D) Kagome lattices using the FMOs of NHC–Au–NHC junctions to create low-dimensional molecular networks exhibiting intrinsic metallicity. Scanning tunneling spectroscopy and first-principles density functional theory reveal the contribution of C–Au–C π-bonding states to dispersive bands that imbue 1D- and 2D-NHC lattices with exceptionally small work functions.
7

Rey, Yannick P., and Ryan Gilmour. "Modulating NHC catalysis with fluorine." Beilstein Journal of Organic Chemistry 9 (December 6, 2013): 2812–20. http://dx.doi.org/10.3762/bjoc.9.316.

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Fluorination often confers a range of advantages in modulating the conformation and reactivity of small molecule organocatalysts. By strategically introducing fluorine substituents, as part of a β-fluoroamine motif, in a triazolium pre-catalyst, it was possible to modulate the behaviour of the corresponding N-heterocyclic carbene (NHC) with minimal steric alterations to the catalyst core. In this study, the effect of hydrogen to fluorine substitution was evaluated as part of a molecular editing study. X-ray crystallographic analyses of a number of derivatives are presented and the conformations are discussed. Upon deprotonation, the fluorinated triazolium salts generate catalytically active N-heterocyclic carbenes, which can then participate in the enantioselective Steglich rearrangement of oxazolyl carbonates to C-carboxyazlactones (e.r. up to 87.0:13.0).
8

Ojha, Minita, Shweta Choudhary, and Raj K. Bansal. "3-Benzylbenzothiazolylidene Carbene Catalyzed Isomerization of Dimethyl Maleate to Dimethyl Fumarate: Experimental and Theoretical Results." Current Organocatalysis 7, no. 2 (July 2, 2020): 108–17. http://dx.doi.org/10.2174/2213337206666191018111354.

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Background: N-Heterocyclic Carbenes (NHCs) have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. Since Arduengo and co-workers first isolated a bottlable NHC, namely imidazol-2-ylidene derivative, these nucleophilic species have attained a prominent place in synthetic organic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods and Results: The quantitative aspects of the experimental and theoretical investigation of isomerization of dimethyl maleate to dimethyl fumarate catalyzed by an N-heterocyclic carbene (NHC), namely 3-benzylbenzothiazolylidene are being reported for the first time. Dimethyl maleate on treating with 3-benzylbenzothiazolylidene carbene (10 mol%), generated in situ from the reaction of 3- benzylbenzothiazolium bromide with triethylamine in diethyl ether at room temperature under nitrogen atmosphere isomerizes quantitatively to dimethyl fumarate. Theoretical investigation of a model reaction scheme at the wB97XD/6-31+G(d) level reveals that initial attack of the carbene, which is the ratedetermining step, is followed by rotation about the C-C bond in preference to a higher activation free energy path involving proton abstraction. The species so formed splits off the carbene to yield dimethyl fumarate. Eyring equation has been used to rationalize the effect of temperature on the isomerization rate. Conclusions and Perspective: 3-Benzylbenzothiazolylidene carbene catalyzes the isomerization of dimethyl maleate to its trans-isomer. This carbene can be used in other catalytic reactions, such as acyloin condensation and Stetter reaction.
9

Zhu, Tingshun, Ke Xu, and Ziyuan Wang. "N-Heterocyclic Carbene-Organocatalyzed Arene Formation: Application in Atroposelective Synthesis of Polysubstituted Benzenes." Synlett 31, no. 10 (February 3, 2020): 925–32. http://dx.doi.org/10.1055/s-0039-1690814.

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In recent decades, organocatalysis by N-heterocyclic carbenes (NHCs) has emerged as a versatile and powerful method in organic synthesis. As a result of the power of NHC organocatalysis to produce cyclic compounds, polysubstituted benzenes, which are among the most important cyclic compounds in organic chemistry, can be synthesized efficiently and selectively. This article briefly summarizes the history of NHC organocatalysis, including recent developments in benzene-formation methods, and highlights our recent work in atroposelective arene formation by carbene-catalyzed formal [4+2] cyclo­additions. We expect that more NHC-catalyzed methods for the synthesis of asymmetric arenes will be developed in the near future, providing shortcuts to syntheses of sophisticated chiral functional molecules with polysubstituted benzene nuclei.
10

Tang, Xiang-Ting, Fan Yang, Ting-Ting Zhang, Yi-Fan Liu, Si-Yu Liu, Tong-Fu Su, Dong-Can Lv, and Wen-Bo Shen. "Recent Progress in N-Heterocyclic Carbene Gold-Catalyzed Reactions of Alkynes Involving Oxidation/Amination/Cycloaddition." Catalysts 10, no. 3 (March 20, 2020): 350. http://dx.doi.org/10.3390/catal10030350.

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Recent rapid development in homogeneous gold catalysis affords an alternative and particularly thriving strategy for the generation of gold carbenes through gold-catalyzed oxidation/amination/cycloaddition of alkynes, while it avoids the employment of hazardous and potentially explosive diazo compounds as starting materials for carbene generation. In addition to facile and secure operation, gold carbenes generated in this strategy display good chemoselectivity distinct from other metal carbenes produced from the related diazo approach. N-heterocyclic carbene (NHC) gold is a special metal complex that can be used as ancillary ligands, which provides enhanced stability and can also act as an efficient chiral directing group. In this review, we will present an overview of these recent advances in alkyne oxidation/amination/cycloaddition by highlighting their specificity and applicability, aiming to facilitate progress in this very exciting area of research.
11

Buchspies, Jonathan, Md Mahbubur Rahman, and Michal Szostak. "Suzuki–Miyaura Cross-Coupling of Amides Using Well-Defined, Air- and Moisture-Stable Nickel/NHC (NHC = N-Heterocyclic Carbene) Complexes." Catalysts 10, no. 4 (March 31, 2020): 372. http://dx.doi.org/10.3390/catal10040372.

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In this Special Issue on N-Heterocyclic Carbenes and Their Complexes in Catalysis, we report the first example of Suzuki–Miyaura cross-coupling of amides catalyzed by well-defined, air- and moisture-stable nickel/NHC (NHC = N-heterocyclic carbene) complexes. The selective amide bond N–C(O) activation is achieved by half-sandwich, cyclopentadienyl [CpNi(NHC)Cl] complexes. The following order of reactivity of NHC ligands has been found: IPr > IMes > IPaul ≈ IPr*. Both the neutral and the cationic complexes are efficient catalysts for the Suzuki–Miyaura cross-coupling of amides. Kinetic studies demonstrate that the reactions are complete in < 1 h at 80 °C. Complete selectivity for the cleavage of exocyclic N-acyl bond has been observed under the experimental conditions. Given the utility of nickel catalysis in activating unreactive bonds, we believe that well-defined and bench-stable [CpNi(NHC)Cl] complexes will find broad application in amide bond and related cross-couplings of bench-stable acyl-electrophiles.
12

Lin, Ivan JB, and Chandra Sekhar Vasam. "Review of gold(I) N-heterocyclic carbenes." Canadian Journal of Chemistry 83, no. 6-7 (June 1, 2005): 812–25. http://dx.doi.org/10.1139/v05-087.

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This review presents an overview of the work on Au(I)–NHC chemistry. The efficiency of different synthetic strategies of Au(I)–NHCs is discussed. Transmetallation of Ag(I)–NHCs appears to be an easy method as compared with the others. The influence of aurophilicity "a traditional property of a Au(I) center" in making the supramolecular assemblies is also covered. The combination of the Au(I) center with NHCs has great potential in the fields of medicine, catalysis, liquid crystal, and optoelectronic.Key words: gold–carbenes, silver–carbenes, carbene transfer, aurophilicity.
13

McQueen, Caitlin M. A., Anthony F. Hill, Chenxi Ma, and Jas S. Ward. "Ruthenium and osmium complexes of dihydroperimidine-based N-heterocyclic carbene pincer ligands." Dalton Transactions 44, no. 47 (2015): 20376–85. http://dx.doi.org/10.1039/c5dt03728j.

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Double geminal aminal C–H activation processes of the dihydroperimidine based NHC pincer pro-ligands H2C(NCH2PR2)2C10H6 are described leading to dihydroperimidinylidene complexes including the first osmium examples.
14

Ellul, Charles E., John P. Lowe, Mary F. Mahon, Paul R. Raithby, and Michael K. Whittlesey. "[Ru3(6-NHC)(CO)10]: synthesis, characterisation and reactivity of rare 46-electron tri-ruthenium clusters." Dalton Transactions 47, no. 13 (2018): 4518–23. http://dx.doi.org/10.1039/c8dt00189h.

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The room temperature reaction of 6-membered ring N-heterocyclic carbenes with [Ru3(CO)12] affords [Ru3(6-NHC)(CO)10], rare examples of coordinatively unsaturated, 46-electron tri-ruthenium clusters. Upon mild heating in the presence of C5H5N, H2 or PPh3, these compounds lose carbene.
15

Liu, Ming, Jan C. Namyslo, Martin Nieger, Mika Polamo, and Andreas Schmidt. "From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer." Beilstein Journal of Organic Chemistry 12 (December 8, 2016): 2673–81. http://dx.doi.org/10.3762/bjoc.12.264.

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The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl)borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol)imidazol-2-ylidene reacts with (triphenylphosphine)gold(I) chloride to give the cationic NHC complex [Au(NHC)2][Cl] by coordination with the carbene carbon atom. The anionic N-heterocyclic carbene 1-(2-phenolate)imidazol-2-ylidene gives the complexes [K][Au(NHC−)2], [Rh(NHC−)3] and [Ni(NHC−)2], respectively. Results of four single crystal analyses are presented.
16

Beig, Nosheen, Varsha Goyal, and Raj Kumar Bansal. "Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review." Beilstein Journal of Organic Chemistry 19 (September 20, 2023): 1408–42. http://dx.doi.org/10.3762/bjoc.19.102.

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N-Heterocyclic carbenes (NHCs) are a special type of carbenes in which the carbene carbon atom is part of the nitrogen heterocyclic ring. Due to the simplicity of their synthesis and the modularity of their stereoelectronic properties, NHCs have unquestionably emerged as one of the most fascinating and well-known species in chemical science. The remarkable stability of NHCs can be attributed to both kinetic as well as thermodynamic effects caused by its structural features. NHCs constitute a well-established class of new ligands in organometallic chemistry. Although initially NHCs were regarded as pure σ-donor ligands, later experimental and theoretical studies established the presence of a significant back donation from the d-orbital of the metal to the π* orbital of the NHC. Over the last two decades, NHC–metal complexes have been extensively used as efficient catalysts in different types of organic reactions. Of these, NHC–Cu(I) complexes found prominence for various reasons, such as ease of preparation, possibility of structural diversity, low cost, and versatile applications. This article overviews applications of NHC–Cu(I) complexes as catalysts in organic synthesis over the last 12 years, which include hydrosilylation reactions, conjugate addition, [3 + 2] cycloaddition, A3 reaction, boration and hydroboration, N–H and C(sp2)–H carboxylation, C(sp2)–H alkenylation and allylation, C(sp2)–H arylation, C(sp2)–H amidation, and C(sp2)–H thiolation. Preceding the section of applications, a brief description of the structure of NHCs, nature of NHC–metal bond, and methods of preparation of NHC–Cu complexes is provided.
17

Quy, Phan Tu, Nguyen Thi Thanh Hai, Tran Thi Ai My, Thanh Q. Bui, Tran Thai Hoa, Nguyen Vinh Phu, Huynh Thi Phuong Loan, and Nguyen Thi Ai Nhung. "A theoretical study on inhibitability of silver(I) N‐heterocyclic carbene and dimer silver(I) N‐heterocyclic carbene complexes against Phytophthora capsici and Fusarium sporotrichioides in Piper nigrum L." Vietnam Journal of Chemistry 59, no. 3 (June 2021): 405–15. http://dx.doi.org/10.1002/vjch.202000163.

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AbstractPiper nigrum L. (black pepper) is highly susceptible to many infectious diseases, especially foot rot caused by Phytophthora capsici and yellow disease caused by Fusarium sporotrichioides. The inhibitability of silver‐carbene Ag‐NHC and di‐silver‐carbene Di‐Ag‐NHC complexes on protein 6KD3 in Phytophthora capsici and protein 1JFA in Fusarium sporotrichioides was theoretically investigated using molecular docking simulation. The results reveal that both Ag‐NHC and Di‐Ag‐NHC performing strong inhibitory effects towards both proteins. Docking score energy values regarding [Ag‐NHC]‐6KD3 and [Di‐Ag‐NHC]‐6KD3 are ‐11.2 and ‐11.7 kcal.mol‐1. The corresponding figures for [Ag‐NHC]‐1JFA and [Di‐Ag‐NHC]‐1JFA are ‐11.1 and ‐13.4 kcal.mol‐1. Also, analysis on hydrogen bonding, interaction distance, and van der Waals interactions formed in the inhibitory systems indicates good site‐site binding between amino acids of the targeted proteins and the carbene molecules. This study introduces Ag‐NHC and Di‐Ag‐NHC complexes as potential candidates for prevention of infection caused by Phytophthora capsici and Fusarium sporotrichioides, thus mitigate the impacts on the production of black pepper.
18

Beig, Nosheen, Varsha Goyal, Raakhi Gupta, and Raj K. Bansal. "N-Heterocyclic Carbenes–CuI Complexes as Catalysts: A Theoretical Insight." Australian Journal of Chemistry 74, no. 7 (2021): 503. http://dx.doi.org/10.1071/ch20332.

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The electronic structures of N-heterocyclic carbenes (NHC) imidazolinylidene, thiazolinylidene, imidazolylidene, thiazolylidene, and 1,2,4-triazolylidene and their complexes with cuprous halides (CuX, X=Cl, Br, I) were investigated theoretically at the B3LYP/def2-SVP level. In contrast to other NHCs, imidazolylidene and 1,2,4-triazolylidene do not dimerize owing to the negligible coefficient of the vacant p-orbital at the carbene centre in their respective LUMOs. This is further supported by their greater thermodynamic and kinetic stabilities revealed by greater activation free energies and smaller standard free energies for their dimerization. Second-order perturbation interactions in the natural bond orbital (NBO) analysis of the NHCs indicate that six π electrons are delocalized in imidazolylidene, thiazolylidene, and 1,2,4-triazolylidene, conferring aromatic character and thereby enhancing their thermodynamic stability. NBO analysis reveals the existence of effective back bonding from a d orbital of Cu to the NHC, increasing the Wiberg bond index of the C–Cu bond to ~1.5. Owing to the large electronic chemical potential (μ) and high nucleophilicity indices, NHCs are able to transfer their electron density effectively to the cuprous halides having low μ values and high electrophilicity indices to yield stable NHC–CuI complexes. Large values of the Fukui function f(r) at the carbene centre of the NHCs and Cu atom of the NHC–CuI complexes indicate their softness. Imidazolylidene was found to be the softest, rationalizing wide use of this class of NHCs as ligands. The coordination of the NHCs to cuprous halides is either barrierless or has a very low activation free energy barrier. In the A3 reaction wherein NHC–Cu(I) complexes are used as catalyst, the reaction of NHC–CuI with phenylacetylene changes the latter into acetylide accompanied by raising the energy level of its HOMO considerably compared with the level of the uncomplexed alkyne, making its reaction with benzaldehyde barrierless.
19

Rupar, Paul A., Michael C. Jennings, and Kim M. Baines. "The reactivity of an anionic gallium N-heterocyclic carbene analogue with a solution stable digermene." Canadian Journal of Chemistry 85, no. 2 (February 1, 2007): 141–47. http://dx.doi.org/10.1139/v07-002.

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The reaction of the anionic gallium(I) N-heterocyclic carbene (NHC) analogue 3 with the solution stable digermene 5 results in the formation of the gallium NHC – germylene complex 8. The gallium NHC – germylene complex 8 was derivatized with CH3I and (CH3)3SiCl.Key words: digermene, carbene analogue, germylene, gallium(I).
20

Zhang, Bo, Yu’ai Duan, Xin Zhang, and Shuai Guo. "Uncommon carbene-to-azole ligand rearrangement of N-heterocyclic carbenes in a ruthenium system." Chemical Communications 57, no. 56 (2021): 6879–82. http://dx.doi.org/10.1039/d1cc01871j.

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21

Sun, Hongsui, Xiao-Yan Yu, Paolo Marcazzan, Brian O. Patrick, and Brian R. James. "Rhodium(I)–(N-heterocyclic carbene)–diphosphine complexes." Canadian Journal of Chemistry 87, no. 9 (September 2009): 1248–54. http://dx.doi.org/10.1139/v09-118.

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Reactions of [RhCl(COE)(IPr)]2 (1) and [RhCl(COE)(IMes)]2 (2) (COE = cyclooctene; IPr = N,N′-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; IMes = N,N′-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) with the diphosphines Ph2P(CH2)nPPh2 and 1,2-bis(diphenylphosphino)benzene (dppbz) give the N-heterocyclic carbene (NHC) – diphosphine – rhodium(I) complexes: RhCl(NHC)[Ph2P(CH2)nPPh2] [NHC = IPr, n = 1 (3); NHC = IMes, n = 1 (4); NHC = IPr, n = 2 (5); NHC = IMes, n = 2 (6); NHC = IPr, n = 4 (7); NHC = IMes, n = 4 (8)] and RhCl(NHC)(dppbz) [NHC = IPr (9); NHC = IMes (10)]. All the complexes are characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy, elemental analysis, and mass spectrometry. Complexes 3, 7, and 9 are also characterized crystallographically. In benzene solution, the complexes decompose in the presence of O2 with formation of the diphosphine dioxide, whereas reaction with CO leads to replacement of the NHC ligand to give known carbonyl–diphosphine complexes.
22

Bysewski, Oliver, Andreas Winter, Phil Liebing, and Ulrich S. Schubert. "Noble Metal Complexes of a Bis-Caffeine Containing NHC Ligand." Molecules 27, no. 13 (July 5, 2022): 4316. http://dx.doi.org/10.3390/molecules27134316.

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N-Heterocyclic carbenes (NHCs) have seen more and more use over the years. The go-to systems that are usually considered are derivatives of benzimidazole or imidazole. Caffeine possesses an imidazole unit and was already utilized as a carbene-type ligand; however, its use within a tridentate bis-NHC system has—to the best of our knowledge—not been reported so far. The synthesis of the ligand is straightforward and metal complexes are readily available via silver-salt metathesis. A platinum(II) and a palladium(II) complex were isolated and a crystal structure of the former was examined. For the Pt(II) complex, luminescence is observed in solid state as well as in solution.
23

Vanden Broeck, Sofie M. P., Fady Nahra, and Catherine S. J. Cazin. "Bulky-Yet-Flexible Carbene Ligands and Their Use in Palladium Cross-Coupling." Inorganics 7, no. 6 (June 21, 2019): 78. http://dx.doi.org/10.3390/inorganics7060078.

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In recent years, several classes of new N-heterocyclic carbene (NHC) ligands were developed around the concept of “flexible steric bulk”. The steric hindrance of these ligands brings stability to the active species, while ligand flexibility still allows for the approach of the substrate. In this review, the synthesis of several types of new classes, such as IBiox, cyclic alkyl amino carbenes (CAAC), ITent, and IPr* are discussed, as well as how they move the state-of-the-art in palladium catalyzed cross-coupling forward.
24

Ho, Peter C., Hilary A. Jenkins, James F. Britten, and Ignacio Vargas-Baca. "Building new discrete supramolecular assemblies through the interaction of iso-tellurazole N-oxides with Lewis acids and bases." Faraday Discussions 203 (2017): 187–99. http://dx.doi.org/10.1039/c7fd00075h.

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The supramolecular macrocycles spontaneously assembled by iso-tellurazole N-oxides are stable towards Lewis bases as strong as N-heterocyclic carbenes (NHC) but readily react with Lewis acids such as BR3 (R = Ph, F). The electron acceptor ability of the tellurium atom is greatly enhanced in the resulting O-bonded adducts, which consequently enables binding to a variety of Lewis bases that includes acetonitrile, 4-dimethylaminopyridine, 4,4′-bipyridine, triphenyl phosphine, a N-heterocyclic carbene and a second molecule of iso-tellurazole N-oxide.
25

Tialiou, Alexia, Jiamin Chin, Bernhard K. Keppler, and Michael R. Reithofer. "Current Developments of N-Heterocyclic Carbene Au(I)/Au(III) Complexes toward Cancer Treatment." Biomedicines 10, no. 6 (June 15, 2022): 1417. http://dx.doi.org/10.3390/biomedicines10061417.

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Since their first discovery, N-heterocyclic carbenes have had a significant impact on organometallic chemistry. Due to their nature as strong σ-donor and π-acceptor ligands, they are exceptionally well suited to stabilize Au(I) and Au(III) complexes in biological environments. Over the last decade, the development of rationally designed NHCAu(I/III) complexes to specifically target DNA has led to a new “gold rush” in bioinorganic chemistry. This review aims to summarize the latest advances of NHCAu(I/III) complexes that are able to interact with DNA. Furthermore, the latest advancements on acyclic diamino carbene gold complexes with anticancer activity are presented as these typically overlooked NHC alternatives offer great additional design possibilities in the toolbox of carbene-stabilized gold complexes for targeted therapy.
26

Prencipe, Filippo, Anna Zanfardino, Michela Di Napoli, Filomena Rossi, Stefano D’Errico, Gennaro Piccialli, Giuseppe Felice Mangiatordi, et al. "Silver (I) N-Heterocyclic Carbene Complexes: A Winning and Broad Spectrum of Antimicrobial Properties." International Journal of Molecular Sciences 22, no. 5 (March 2, 2021): 2497. http://dx.doi.org/10.3390/ijms22052497.

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The evolution of antibacterial resistance has arisen as the main downside in fighting bacterial infections pushing researchers to develop novel, more potent and multimodal alternative drugs.Silver and its complexes have long been used as antimicrobial agents in medicine due to the lack of silver resistance and the effectiveness at low concentration as well as to their low toxicities compared to the most commonly used antibiotics. N-Heterocyclic Carbenes (NHCs) have been extensively employed to coordinate transition metals mainly for catalytic chemistry. However, more recently, NHC ligands have been applied as carrier molecules for metals in anticancer applications. In the present study we selected from literature two NHC-carbene based on acridinescaffoldand detailed nonclassicalpyrazole derived mono NHC-Ag neutral and bis NHC-Ag cationic complexes. Their inhibitor effect on bacterial strains Gram-negative and positivewas evaluated. Imidazolium NHC silver complex containing the acridine chromophore showed effectiveness at extremely low MIC values. Although pyrazole NHC silver complexes are less active than the acridine NHC-silver, they represent the first example of this class of compounds with antimicrobial properties. Moreover all complexesare not toxic and they show not significant activity againstmammalian cells (Hek lines) after 4 and 24 h. Based on our experimental evidence, we are confident that this promising class of complexes could represent a valuable starting point for developing candidates for the treatment of bacterial infections, delivering great effectiveness and avoiding the development of resistance mechanisms.
27

Hock, Andreas, Luis Werner, Christian Luz, and Udo Radius. "N-Heterocyclic carbene and cyclic (alkyl)(amino)carbene adducts of gallium hydrides, gallium chlorides and gallium hydrochlorides." Dalton Transactions 49, no. 32 (2020): 11108–19. http://dx.doi.org/10.1039/d0dt02070b.

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A detailed study on the synthesis and characterization of NHC gallane adducts (NHC)·GaH3, (NHC)·GaH2Cl, and (NHC)·GaHCl2 and the reactivity of these adducts with the cyclic (alkyl)(amino)carbene cAACMe is presented.
28

Fontes, F. A. O., K. K. P. Gomes, Francisca de Fatima P. Medeiros, C. P. Souza, J. F. Sousa, and Uilame Umbelino Gomes. "Synthesis of Niobium Carbide from Ammonium Niobium (V) Oxalate Precursor at Low Temperature in Rotating Cylinder Reactor." Materials Science Forum 498-499 (November 2005): 747–0. http://dx.doi.org/10.4028/www.scientific.net/msf.498-499.747.

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The reaction of oxalic precursor {(NH4)3[NbO(C2O4)3]H2O}, was prepared from the Nb2O5, to niobium carbide (NbC) were performed in a rotating cylinder reactor scale-lab designed to niobium carbide powders synthesis at low temperature (1173 K). The NbC was prepared by a oxalic precursor and as well of commercial niobium pentoxide under flowing CH4- H2 mixtures. The reactor was heated through a bi-partied electric furnace with programmable temperature. The reaction overall time was determined from the curve of methane absorption evolution by gas chromatograph (FID) analysis. The preliminary results showed that the conversion function depends on the rotation, temperature, mixture flow, CH4/H2 ratio and heating rate. The niobium carbide was characterized through X-ray diffraction and compared to the commercial products. The reaction of oxalic precursor {(NH4)3[NbO(C2O4)3]H2O} to niobium carbide (NbC) in 3% (v/v) CH4/H2 yielded smallest grain size as well smaller overall time when compared with obtained direct by commercial Nb2O5, however it had small mass conversion due the solid carryover not controlled.
29

Zhang, Dongxiang, Jie Li, Xiao Dong, Xing Zhou, Zhi Yang, and Herbert W. Roesky. "N-Heterocyclic Carbene-facilated Condensation of 3-Methylphenylboronic Acid to the Boroxine." Zeitschrift für Naturforschung B 68, no. 5-6 (June 1, 2013): 453–57. http://dx.doi.org/10.5560/znb.2013-2342.

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The adduct of (3-MeC6H4)3B3O3 with an N-heterocyclic carbene (NHC=1,3-diethyl-4,5- dimethylimidazol-2-ylidene) was prepared by reacting 2.5 equiv. of 3-methylphenylboronic acid with 1 equiv. of the NHC. This reaction shows a novel carbene-facilitated condensation of substituted phenylboronic acid monomers. The structure of the compound (3-MeC6H4)3B3O3(NHC) (1) has been characterized by 1H NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction studies
30

Haslinger, S., A. C. Lindhorst, J. W. Kück, M. Cokoja, A. Pöthig, and F. E. Kühn. "Isocyanide substitution reactions at the trans labile sites of an iron(ii) N-heterocyclic carbene complex." RSC Advances 5, no. 104 (2015): 85486–93. http://dx.doi.org/10.1039/c5ra18270k.

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A variety of isocyanide-substituted Fe(ii) N-heterocyclic carbene (NHC) complexes has been synthesized, starting from an Fe(ii) NHC complex with an equatorial, tetradentate bis(pyridyl-NHC) ligand (NCCN).
31

Crochet, Pascale, and Victorio Cadierno. "Gold Complexes with Hydrophilic N-Heterocyclic Carbene Ligands and Their Contribution to Aqueous-Phase Catalysis." Catalysts 13, no. 2 (February 17, 2023): 436. http://dx.doi.org/10.3390/catal13020436.

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N-Heterocyclic carbenes (NHCs) are nowadays one of the most widely employed ligands in organometallic chemistry and homogeneous catalysis due to the inherent stability of the metal-carbene bond and the ease of modification of the backbone as well as the N-wingtips substituents of these ligands. The functionalization of NHCs with hydrophilic groups offers the possibility of using NHC-metal complexes in aqueous catalysis, a hot topic within the Green Chemistry context due to the positive implications associated with the use of water as a reaction medium. In line with the enormous interest aroused by gold complexes in catalysis, significant efforts have been directed in the last years to the design and application of hydrophilic NHC-gold catalysts. This review is aimed to summarize the research in this area. The catalytic applications of water-soluble gold nanoparticles stabilized by hydrophilic NHCs are also covered.
32

Wang, Yu-Ting, Bin-Bin Gao, Fan Wang, Shi-Yuan Liu, Hong Yu, Wen-Hua Zhang, and Jian-Ping Lang. "Palladium(ii) and palladium(ii)–silver(i) complexes with N-heterocyclic carbene and zwitterionic thiolate mixed ligands: synthesis, structural characterization and catalytic properties." Dalton Transactions 46, no. 6 (2017): 1832–39. http://dx.doi.org/10.1039/c6dt04599e.

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33

Thi Thanh Hai, Nguyen, Thanh Q. Bui, Tran Thi Ai My, Huynh Thi Phuong Loan, Tran Thai Hoa, Phan Tu Quy, Nguyen Thi Thu Thuy, Dang Thanh Nhan, and Nguyen Thi Ai Nhung. "In Silico Inhibitability of Copper Carbenes and Silylenes against Rhizoctonia solani and Magnaporthe oryzae." Journal of Chemistry 2021 (December 30, 2021): 1–14. http://dx.doi.org/10.1155/2021/5555521.

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Copper lighter tetrylenes are promising for inhibition towards Rhizoctonia solani-based protein PDB-4G9M and Magnaporthe oryzae-based PDB-6JBR in rice. Quantum properties of four hypothetic copper complexes of carbenes and silylenes (Cu-NHC1, Cu-NHC2, Cu-NHSi1, and Cu-NHSi2) were examined using the density functional theory. Their inhibitability towards the targeted proteins was evaluated using molecular docking simulation. Quantum analysis predicts the stability of the investigated complexes and thus their practical existability and practicable synthesisability. Their electronic configurations are justified as highly conducive to intermolecular interaction. Regarding ligand-protein as carbenes/silylenes-4G9M inhibitory structures, the stability is estimated in the order [Cu-NHC2]-4G9M (DS −12.9 kcal⋅mol−1) > [Cu-NHSi1]-4G9M (DS −11.8 kcal⋅mol−1) = [Cu-NHSi2]-4G9M (DS −11.7 kcal⋅mol−1) > [Cu-NHC1]-4G9M (DS –11.4 kcal⋅mol−1). In contrast, the corresponding order for the carbenes/silylenes-6JBR systems is [Cu-NHSi2]-6JBR (DS –13.4 kcal⋅mol−1) > [Cu-NHC2]-6JBR (DS −13.0 kcal⋅mol−1) = [Cu-NHSi1]-6JBR (DS −12.6 kcal⋅mol−1) > [Cu-NHC1]-6JBR (DS −12.3 kcal⋅mol−1). In theory, this study suggests a potentiality of copper lighter tetrylenes and their derivatives against the infection of fungi Rhizoctonia solani and Magnaporthe oryzae, thus encouraging attempts for experimental developments.
34

Jacobsen, Heiko, Andrea Correa, Albert Poater, Chiara Costabile, and Luigi Cavallo. "Understanding the M(NHC) (NHC=N-heterocyclic carbene) bond." Coordination Chemistry Reviews 253, no. 5-6 (March 2009): 687–703. http://dx.doi.org/10.1016/j.ccr.2008.06.006.

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35

Suduwella, Thilini Malsha, Vikram Singh, Mark Aloisio, Ahmadreza Nezamzadeh Ezhieh, Cathleen Crudden, Janine Mauzeroll, and Yuanjiao Li. "Electrochemical Deposition of N-Heterocyclic Carbene on Steels As a Corrosion Protective Layer." ECS Meeting Abstracts MA2023-02, no. 13 (December 22, 2023): 1133. http://dx.doi.org/10.1149/ma2023-02131133mtgabs.

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Steels play a vital role in every aspect of day-to-day life. They are major components in construction, transportation, medicine, and etc. Despite their larger usability, steels are suffering from inevitable corrosion. Hence, finding a sustainable solution for corrosion has been a hot topic in the research field for centuries. One extensively studied strategy is applying a protective layer on top of metals. The recent findings show that N-heterocyclic carbene (NHC) has the potency to form a carbon-metal bond through self-assembling1 or electrochemical deposition2 on different metals such as Au, Pt, Pd, and Ag. Herein, we are trying to coat NHC on mild steel (MS) through electrochemical deposition to act as a corrosion protective layer. Deposition conditions will be optimized by varying the material concentrations, applied voltages, time durations, and substrate roughness. The NHC-coated surface is characterized by X-ray Photoelectron Spectroscopy (XPS), Matrix-Assisted Laser Desorption/Ionization (MALDI), and Atomic Force Microscope-Infrared Spectroscopy (AFM-IR). In addition, the contact angle measurements can be attributed to visualizing the differences in coatings under different conditions. The corrosion studies are utilized to understand the corrosion-resistant properties of the NHC coating. Moreover, the NHC moiety can be modified to perform better to inhibit corrosion and improve the properties of mild steel on their applications. Ultimately, this benchtop approach will be utilized and tested on a large scale and industrial level. (1) Crudden, C. M.; Horton, J. H.; Ebralidze, I. I.; Zenkina, O. V.; McLean, A. B.; Drevniok, B.; She, Z.; Kraatz, H.-B.; Mosey, N. J.; Seki, T. Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold. Nat. Chem. 2014, 6 (5), 409-414. (2) Amit, E.; Dery, L.; Dery, S.; Kim, S.; Roy, A.; Hu, Q.; Gutkin, V.; Eisenberg, H.; Stein, T.; Mandler, D. Electrochemical deposition of N-heterocyclic carbene monolayers on metal surfaces. Nat. Commun. 2020, 11 (1), 1-10.
36

Azpíroz, Ramón, Mert Olgun Karataş, Vincenzo Passarelli, Ismail Özdemir, Jesús J. Pérez-Torrente, and Ricardo Castarlenas. "Preparation of Mixed Bis-N-Heterocyclic Carbene Rhodium(I) Complexes." Molecules 27, no. 20 (October 18, 2022): 7002. http://dx.doi.org/10.3390/molecules27207002.

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A series of mixed bis-NHC rhodium(I) complexes of type RhCl(η2-olefin)(NHC)(NHC’) have been synthesized by a stepwise reaction of [Rh(μ-Cl)(η2-olefin)2]2 with two different NHCs (NHC = N-heterocyclic carbene), in which the steric hindrance of both NHC ligands and the η2-olefin is critical. Similarly, new mixed coumarin-functionalized bis-NHC rhodium complexes have been prepared by a reaction of mono NHC complexes of type RhCl(NHC-coumarin)(η2,η2-cod) with the corresponding azolium salt in the presence of an external base. Both synthetic procedures proceed selectively and allow the preparation of mixed bis-NHC rhodium complexes in good yields.
37

Kelemen, Z., R. Streubel, and L. Nyulászi. "Zwitterionic carbene adducts and their carbene isomers." RSC Advances 5, no. 52 (2015): 41795–802. http://dx.doi.org/10.1039/c5ra07039b.

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38

Boubakri, L., S. Yasar, V. Dorcet, T. Roisnel, C. Bruneau, N. Hamdi, and I. Ozdemir. "Synthesis and catalytic applications of palladium N-heterocyclic carbene complexes as efficient pre-catalysts for Suzuki–Miyaura and Sonogashira coupling reactions." New Journal of Chemistry 41, no. 12 (2017): 5105–13. http://dx.doi.org/10.1039/c7nj00488e.

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A new palladium complex series with N-heterocyclic carbene (NHC), pyridine and phosphine ligands, PdCl2(L)NHC (2a–c)(L = NHC), PdCl2(L1)NHC(3a–c)(L1 = pyridine), PdCl2(L2)NHC(4a–c)(L2 = triphenylphosphine) was synthesised and fully characterized.
39

Zhang, Guowen, Man Chao, Shuting Wang, Mengxia Zhu, Dou Wang, Guangsheng Pang, and Yanhui Shi. "Synthesis and Catalytic Activity of Chiral Dicarbene Dipalladium Complexes Incorporating the S-binaphthol Unit." Journal of Chemical Research 42, no. 1 (January 2018): 54–56. http://dx.doi.org/10.3184/174751918x15168768395864.

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A series of chiral di-N-heterocyclic carbene (NHC) dipalladium complexes, [{PdPyCl2}2(di-NHC)], in which di-NHC represents a di-imidazolylidene, featuring an (S)-3,3′-dimethyl-2,2′-dimethoxy-1,1′-binaphthalene spacer between the carbene units, have been prepared. The influence of ligand size on the catalytic activity of these complexes in the Suzuki reaction of phenylboronic acid with p-bromotoluene has been investigated. The most sterically hindered complex, bearing the di-isopropylphenyl group, showed the greatest catalytic activity, and it is active for various aryl halides with different electronic and steric properties.
40

Jahnke, Mareike C., Tania Pape, and F. Ekkehardt Hahn. "Ligand Exchange at a Gold(I) Carbene Complex." Zeitschrift für Naturforschung B 68, no. 5-6 (June 1, 2013): 467–73. http://dx.doi.org/10.5560/znb.2013-3076.

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Gold complex [AuCl(NHC)] (NHC=N,N0-dipropylbenzimidazolin-2-ylidene) 1 undergoes facile substitution reactions at the gold(I) center. Treatment of 1 with anionic phenylacetylide or thiophenolate led to the neutral gold complexes 2 and 3, respectively. The cationic gold complexes [Au(NHC)(pyridine)](BF4) [4]BF4 and [Au2(NHC)2(4,4'-bipyridine)](BF4)2 [5](BF4)2 were obtained via abstraction of the chloro ligand from 1 and reaction with the appropriate amine. Reaction of 1 with AgBF4 in the presence of PPh3 instead of an amine led to an inseparable product mixture of the mixed NHC=PPh3 complex [6]BF4, the dicarbene complex [Au(NHC)2]BF4, [7]BF4, and [Au(PPh3)2]BF4, [8]BF4. Crystals of 2 and [6]BF4 were obtained, and X-ray diffraction structure analyses revealed that the gold(I) atoms are coordinated in a linear fashion by the NHC and the co-ligand
41

Köppe, R., and H. Schnöckel. "The boron–boron triple bond? A thermodynamic and force field based interpretation of the N-heterocyclic carbene (NHC) stabilization procedure." Chemical Science 6, no. 2 (2015): 1199–205. http://dx.doi.org/10.1039/c4sc02997f.

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From thermodynamic and force constant discussion a new description of bonding of B2(NHC)2 (NHC = N-heterocyclic carbene C3N2H2(C6H3Pri2-2,6)2) as NHCBBNHC rather than NHC→BB←NHC is given.
42

Leitão, Maria Inês P. S., Giulia Francescato, Clara S. B. Gomes, and Ana Petronilho. "Synthesis of Platinum(II) N-Heterocyclic Carbenes Based on Adenosine." Molecules 26, no. 17 (September 4, 2021): 5384. http://dx.doi.org/10.3390/molecules26175384.

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Organometallic derivatization of nucleosides is a highly promising strategy for the improvement of the therapeutic profile of nucleosides. Herein, a methodology for the synthesis of metalated adenosine with a deprotected ribose moiety is described. Platinum(II) N-heterocyclic carbene complexes based on adenosine were synthesized, namely N-heterocyclic carbenes bearing a protected and unprotected ribose ring. Reaction of the 8-bromo-2′,3′,5′-tri-O-acetyladenosine with Pt(PPh3)4 by C8−Br oxidative addition yielded complex 1, with a PtII centre bonded to C-8 and an unprotonated N7. Complex 1 reacted at N7 with HBF4 or methyl iodide, yielding protic carbene 2 or methyl carbene 3, respectively. Deprotection of 1 to yield 4 was achieved with NH4OH. Deprotected compound 4 reacted at N7 with HCl solutions to yield protic NHC 5 or with methyl iodide yielding methyl carbene 6. Protic N-heterocyclic carbene 5 is not stable in DMSO solutions leading to the formation of compound 7, in which a bromide was replaced by chloride. The cis-influence of complexes 1–7 was examined by 31P{1H} and 195Pt NMR. Complexes 2, 3, 5, 6 and 7 induce a decrease of 1JPt,P of more than 300 Hz, as result of the higher cis-influence of the N-heterocyclic carbene when compared to the azolato ligand in 1 and 4.
43

Roy, Matthew M. D., Michael J. Ferguson, Robert McDonald, and Eric Rivard. "Approaching monocoordination at a silver(i) cation." Chemical Communications 54, no. 5 (2018): 483–86. http://dx.doi.org/10.1039/c7cc08418h.

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44

Dhara, Debabrata, Pankaj Kalita, Subhadip Mondal, Ramakirushnan Suriya Narayanan, Kaustubh R. Mote, Volker Huch, Michael Zimmer, et al. "Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination." Chemical Science 9, no. 18 (2018): 4235–43. http://dx.doi.org/10.1039/c8sc00348c.

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45

Bensalah, Donia, Nevin Gurbuz, Ismail Özdemir, Rafik Gatri, Lamjed Mansour, and Naceur Hamdi. "Synthesis, Characterization, Antimicrobial Properties, and Antioxidant Activities of Silver-N-Heterocyclic Carbene Complexes." Bioinorganic Chemistry and Applications 2023 (May 26, 2023): 1–15. http://dx.doi.org/10.1155/2023/3066299.

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The emergence of antimicrobial resistance has become a major handicap in the fight against bacterial infections, prompting researchers to develop new, more effective, and multimodal alternatives. Silver and its complexes have long been used as antimicrobial agents in medicine because of their lack of resistance to silver, their low potency at low concentrations, and their low toxicity compared to most commonly used antibiotics. N-Heterocyclic carbenes (NHCs) are widely used for coordination of transition metals, mainly in catalytic chemistry. In this study, several N-alkylated benzimidazolium salts 2a–j were synthesized. Then, the N-heterocyclic carbene (NHC) precursor was treated with Ag2O to give silver (I) NHC complexes (3a–j) at room temperature in dichloromethane for 48 h. Ten new silver-NHC complexes were fully characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS (for complexes) techniques. The antibacterial and antioxidant activities of salt 2 and its silver complex 3 were evaluated. All of these complexes were more effective against bacterial strains than comparable ligands. With MIC values ranging from 6.25 to 100 g/ml, the Ag-NHC complex effectively showed strong antibacterial activity. Antioxidant activity was also tested using conventional techniques, such as 2, 2-diphenyl-1-picrylhydrazine (DPPH) and hydrogen peroxide scavenging assays. In DPPH and ABTS experiments, compounds 3a, 3b, 3c, 3e, 3g, and 3i showed significant clearance.
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Binobaid, Abeer, Kingsley J. Cavell, Mikhail S. Nechaev, and Benson M. Kariuki. "Novel Intramolecular CAryl–S Bond Activation by an Electron Rich, Ring-Expanded-NHC-Rh centre: A Combined Experimental and DFT Study." Australian Journal of Chemistry 64, no. 8 (2011): 1141. http://dx.doi.org/10.1071/ch11243.

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The reaction of (o-MeSPh)-N-functionalized tetrahydropyrimidinium salts with KN(SiMe3)2 and [Rh(COD)Cl]2 in THF leads to the formation of a novel dimeric RhIII bis-carbene complex. The reaction involves the unexpected cleavage/oxidative addition of the aryl-sulfur bond to give dimeric metallated RhIII with bridging MeS< moieties. This unusual reaction is probably a consequence of the sterically imposing structure and strong donor capacity of ring-expanded N-heterocyclic carbenes (RE-NHCs). An X-ray structure of the [(Ph,DIPP-NHC)Rh(Cl)(SMe)2] product complex has been obtained, and DFT studies were undertaken to gain an insight into the reaction pathway.
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Lewis-Alleyne, Lesley C., Bassem S. Bassil, Tobias Böttcher, and Gerd-Volker Röschenthaler. "Selective synthesis of cis- and trans-[(NHCMe)2PtCl2] and [NHCMePt(cod)Cl][NHCMePtCl3] using NHCMeSiCl4." Dalton Trans. 43, no. 42 (2014): 15700–15703. http://dx.doi.org/10.1039/c4dt02214a.

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NHCMeSiCl4 was used to selectively synthesise cis and trans-[(NHCMe)2PtCl2], as well as [NHCMePt(cod)Cl][NHCMePtCl3], which revealed the first ever N-heterocyclic carbene analogue of the Cossa's salt anion.
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Duan, Yulian, Tao Wang, Qingxiao Xie, Xiaobo Yu, Weijie Guo, Jianhui Wang, and Guiyan Liu. "Highly efficient nitrogen chelated ruthenium carbene metathesis catalysts." Dalton Transactions 45, no. 48 (2016): 19441–48. http://dx.doi.org/10.1039/c6dt03899a.

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Yang, Longhua, Yanli Yuan, Hongming Wang, Ning Zhang, and Sanguo Hong. "Theoretical insights into copper(i)–NHC-catalyzed C–H carboxylation of terminal alkynes with CO2: the reaction mechanisms and the roles of NHC." RSC Adv. 4, no. 61 (2014): 32457–66. http://dx.doi.org/10.1039/c4ra00254g.

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Raed, Anas Abo, Vasudevan Dhayalan, Shahar Barkai, and Anat Milo. "N-Heterocyclic Carbene Triazolium Salts Containing Brominated Aromatic Motifs: Features and Synthetic Protocol." CHIMIA International Journal for Chemistry 74, no. 11 (November 25, 2020): 878–82. http://dx.doi.org/10.2533/chimia.2020.878.

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In this work, we provide a brief overview of the role of N-aryl substituents on triazolium N-heterocyclic carbene (NHC) catalysis. This synopsis provides context for the disclosed synthetic protocol for new chiral N-heterocyclic carbene (NHC) triazolium salts with brominated aromatic motifs. Incorporating brominated aryl rings into NHC structures is challenging, probably due to the substantial steric and electronic influence these substituents exert throughout the synthetic protocol. However, these exact characteristics make it an interesting N-aryl substituent, because the electronic and steric diversity it offers could find broad use in organometallic- and organo-catalysis. Following the synthetic reaction by NMR guided the extensive modification of a known protocol to enable the preparation of these challenging NHC pre-catalysts.
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