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Автор: Grafiati

Опубліковано: 6 вересня 2023

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1

Winkelmann, Ole, Christian Näther, and Ulrich Lüning. "Bimacrocyclic NHC transition metal complexes." Journal of Organometallic Chemistry 693, no. 6 (March 2008): 923–32. http://dx.doi.org/10.1016/j.jorganchem.2007.11.064.

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2

Yamaguchi, Yoshitaka. "Synthesis of Transition-metal NHC Complexes using “Protected” NHC Adduct." Bulletin of Japan Society of Coordination Chemistry 52 (2008): 43–54. http://dx.doi.org/10.4019/bjscc.52.43.

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3

Weiss, Daniel T., Philipp J. Altmann, Stefan Haslinger, Christian Jandl, Alexander Pöthig, Mirza Cokoja, and Fritz E. Kühn. "Structural diversity of late transition metal complexes with flexible tetra-NHC ligands." Dalton Transactions 44, no. 42 (2015): 18329–39. http://dx.doi.org/10.1039/c5dt02386f.

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4

Yang, Shiyi, Tongliang Zhou, Xiang Yu, and Michal Szostak. "Ag–NHC Complexes in the p-Activation of Alkynes." Molecules 28, no. 3 (January 18, 2023): 950. http://dx.doi.org/10.3390/molecules28030950.

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Анотація:

Silver–NHC (NHC = N-heterocyclic carbene) complexes play a special role in the field of transition-metal complexes due to (1) their prominent biological activity, and (2) their critical role as transfer reagents for the synthesis of metal-NHC complexes by transmetalation. However, the application of silver–NHCs in catalysis is underdeveloped, particularly when compared to their group 11 counterparts, gold–NHCs (Au–NHC) and copper–NHCs (Cu–NHC). In this Special Issue on Featured Reviews in Organometallic Chemistry, we present a comprehensive overview of the application of silver–NHC complexes in the p-activation of alkynes. The functionalization of alkynes is one of the most important processes in chemistry, and it is at the bedrock of organic synthesis. Recent studies show the significant promise of silver–NHC complexes as unique and highly selective catalysts in this class of reactions. The review covers p-activation reactions catalyzed by Ag–NHCs since 2005 (the first example of p-activation in catalysis by Ag–NHCs) through December 2022. The review focuses on the structure of NHC ligands and p-functionalization methods, covering the following broadly defined topics: (1) intramolecular cyclizations; (2) CO2 fixation; and (3) hydrofunctionalization reactions. By discussing the role of Ag–NHC complexes in the p-functionalization of alkynes, the reader is provided with an overview of this important area of research and the role of Ag–NHCs to promote reactions that are beyond other group 11 metal–NHC complexes.

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5

Visbal, Renso, and M. Concepción Gimeno. "N-heterocyclic carbene metal complexes: photoluminescence and applications." Chem. Soc. Rev. 43, no. 10 (2014): 3551–74. http://dx.doi.org/10.1039/c3cs60466g.

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6

Neshat, Abdollah, Piero Mastrorilli, and Ali Mousavizadeh Mobarakeh. "Recent Advances in Catalysis Involving Bidentate N-Heterocyclic Carbene Ligands." Molecules 27, no. 1 (December 24, 2021): 95. http://dx.doi.org/10.3390/molecules27010095.

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Since the discovery of persistent carbenes by the isolation of 1,3-di-l-adamantylimidazol-2-ylidene by Arduengo and coworkers, we witnessed a fast growth in the design and applications of this class of ligands and their metal complexes. Modular synthesis and ease of electronic and steric adjustability made this class of sigma donors highly popular among chemists. While the nature of the metal-carbon bond in transition metal complexes bearing N-heterocyclic carbenes (NHCs) is predominantly considered to be neutral sigma or dative bonds, the strength of the bond is highly dependent on the energy match between the highest occupied molecular orbital (HOMO) of the NHC ligand and that of the metal ion. Because of their versatility, the coordination chemistry of NHC ligands with was explored with almost all transition metal ions. Other than the transition metals, NHCs are also capable of establishing a chemical bond with the main group elements. The advances in the catalytic applications of the NHC ligands linked with a second tether are discussed. For clarity, more frequently targeted catalytic reactions are considered first. Carbon–carbon coupling reactions, transfer hydrogenation of alkenes and carbonyl compounds, ketone hydrosilylation, and chiral catalysis are among highly popular reactions. Areas where the efficacy of the NHC based catalytic systems were explored to a lesser extent include CO2 reduction, C-H borylation, alkyl amination, and hydroamination reactions. Furthermore, the synthesis and applications of transition metal complexes are covered.

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7

Savchuk, Mariia, Lucas Bocquin, Muriel Albalat, Marion Jean, Nicolas Vanthuyne, Paola Nava, Stéphane Humbel, Damien Hérault, and Hervé Clavier. "Transition metal complexes bearing atropisomeric saturated NHC ligands." Chirality 34, no. 1 (November 5, 2021): 13–26. http://dx.doi.org/10.1002/chir.23378.

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8

Scattolin, Thomas, and Steven P. Nolan. "Synthetic Routes to Late Transition Metal–NHC Complexes." Trends in Chemistry 2, no. 8 (August 2020): 721–36. http://dx.doi.org/10.1016/j.trechm.2020.06.001.

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9

Zhang, Dao, and Guofu Zi. "N-heterocyclic carbene (NHC) complexes of group 4 transition metals." Chemical Society Reviews 44, no. 7 (2015): 1898–921. http://dx.doi.org/10.1039/c4cs00441h.

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10

Messelberger, Julian, Annette Grünwald, Philipp Stegner, Laura Senft, Frank W. Heinemann та Dominik Munz. "Transmetalation from Magnesium–NHCs—Convenient Synthesis of Chelating π-Acidic NHC Complexes". Inorganics 7, № 5 (22 травня 2019): 65. http://dx.doi.org/10.3390/inorganics7050065.

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Анотація:

The synthesis of chelating N-heterocyclic carbene (NHC) complexes with considerable π-acceptor properties can be a challenging task. This is due to the dimerization of free carbene ligands, the moisture sensitivity of reaction intermediates or reagents, and challenges associated with the workup procedure. Herein, we report a general route using transmetalation from magnesium–NHCs. Notably, this route gives access to transition-metal complexes in quantitative conversion without the formation of byproducts. It therefore produces transition-metal complexes outperforming the conventional routes based on free or lithium-coordinated carbene, silver complexes, or in situ metalation in dimethyl sulfoxide (DMSO). We therefore propose transmetalation from magnesium–NHCs as a convenient and general route to obtain NHC complexes.

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11

Mostafa, Mohamed A. B. "Review Study of Chiral N-Heterocyclic Carbene (NHC) Ligands in Stereoselective Metal-Catalyzed Reduction Reactions." Scientific Journal for Faculty of Science-Sirte University 2, no. 1 (April 17, 2022): 116–25. http://dx.doi.org/10.37375/sjfssu.v2i1.210.

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Stereoselective metal-catalyzed reactions using N-heterocyclic carbene (NHC) ligands have shown significant recent advances, due to the ability of NHC ligands as strong σ-donor species to coordinate with a wide variety of transition metals. Therefore, the design of new ligands and the subsequent strategies for their synthesis enables new applications of their metal complexes in catalysis to be investigated. This study focuses on the applications of different classes of Ir-, Pd- , Au- and Rh-NHC ligand complexes as promising catalysts in the asymmetric hydrogenation, hydrosilylation and transfer hydrogenation reactions.

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12

Gao, Pengcheng, and Michal Szostak. "Hydration reactions catalyzed by transition metal–NHC (NHC = N-heterocyclic carbene) complexes." Coordination Chemistry Reviews 485 (June 2023): 215110. http://dx.doi.org/10.1016/j.ccr.2023.215110.

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13

Ohki, Yasuhiro, and Hidetake Seino. "N-Heterocyclic carbenes as supporting ligands in transition metal complexes of N2." Dalton Transactions 45, no. 3 (2016): 874–80. http://dx.doi.org/10.1039/c5dt04298d.

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14

Ruamps, Mirko, Stéphanie Bastin, Lionel Rechignat, Alix Sournia-Saquet, Laure Vendier, Noël Lugan, Jean-Marie Mouesca, Dmitry A. Valyaev, Vincent Maurel, and Vincent César. "Redox-Switchable Behavior of Transition-Metal Complexes Supported by Amino-Decorated N-Heterocyclic Carbenes." Molecules 27, no. 12 (June 11, 2022): 3776. http://dx.doi.org/10.3390/molecules27123776.

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The coordination chemistry of the N-heterocyclic carbene ligand IMes(NMe2)2, derived from the well-known IMes ligand by substitution of the carbenic heterocycle with two dimethylamino groups, was investigated with d6 [Mn(I), Fe(II)], d8 [Rh(I)], and d10 [Cu(I)] transition-metal centers. The redox behavior of the resulting organometallic complexes was studied through a combined experimental/theoretical study, involving electrochemistry, EPR spectroscopy, and DFT calculations. While the complexes [CuCl(IMes(NMe2)2)], [RhCl(COD)(IMes(NMe2)2)], and [FeCp(CO)2 (IMes(NMe2)2)](BF4) exhibit two oxidation waves, the first oxidation wave is fully reversible but only for the first complex the second oxidation wave is reversible. The mono-oxidation event for these complexes occurs on the NHC ligand, with a spin density mainly located on the diaminoethylene NHC-backbone, and has a dramatic effect on the donating properties of the NHC ligand. Conversely, as the Mn(I) center in the complex [MnCp(CO)2 ((IMes(NMe2)2)] is easily oxidizable, the latter complex is first oxidized on the metal center to form the corresponding cationic Mn(II) complex, and the NHC ligand is oxidized in a second reversible oxidation wave.

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15

Lorber, Christian, and Laure Vendier. "Synthesis and structure of early transition metal NHC complexes." Dalton Transactions, no. 35 (2009): 6972. http://dx.doi.org/10.1039/b905056f.

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16

He, Fen, Xin Yang, Zhi-Yue Tian, Han-Guang Wang, and Ying Xue. "Theoretical investigation on the structures and bonding properties of Pd(II), Pt(II) and Ni(II) complexes with tridentate CNC-pincer N-heterocyclic carbene ligands." Journal of Theoretical and Computational Chemistry 15, no. 05 (August 2016): 1650037. http://dx.doi.org/10.1142/s0219633616500371.

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The density functional theory (DFT) has been applied for the analysis of the bond between group 10 metals and N-heterocyclic carbene (NHC) in complexes (MCl(L-X): M [Formula: see text] Pd(II), Pt(II), and Ni(II), L-X[Formula: see text][2-(3-methylimidazolin-4,5-bisX-2-yliden-1-yl)-4-phenyl] amido, X [Formula: see text]H, Cl and CN). Full geometry optimizations have been performed for all the ligands (L-X[Formula: see text] anions), MCl[Formula: see text] cations, and the complexes. In the ligands, the energy levels of the carbon [Formula: see text] lone-pair orbitals suggest the trend L-H[Formula: see text] L-Cl[Formula: see text] L-CN[Formula: see text] for the donor strength. The role of the M–NHC interaction in complexes was investigated by natural bond orbital (NBO) analysis. The results show that the NHC–M bond consists of the components originating from the L[Formula: see text]M donation and the M[Formula: see text]Carbene C back-donation and the metal[Formula: see text]the ring of NHC back-donation. The transition-metal strongly affects the donation and back-donation. The interaction between the metal and the NHC ligand can be influenced by the central metal and the substituent on the ring of NHC.

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17

Kolaříková, V., O. Šimůnek, M. Rybáčková, J. Cvačka, A. Březinová, and J. Kvíčala. "Transition metal complexes bearing NHC ligands substituted with secondary polyfluoroalkyl groups." Dalton Transactions 44, no. 45 (2015): 19663–73. http://dx.doi.org/10.1039/c5dt02258d.

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18

Schaper, Lars-Arne, Sebastian J. Hock, Wolfgang A. Herrmann, and Fritz E. Kühn. "Synthesis and Application of Water-Soluble NHC Transition-Metal Complexes." Angewandte Chemie International Edition 52, no. 1 (November 9, 2012): 270–89. http://dx.doi.org/10.1002/anie.201205119.

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19

Baczewska, Paulina, Katarzyna Śniady, Wioletta Kośnik, and Michał Michalak. "Acenaphthene-Based N-Heterocyclic Carbene Metal Complexes: Synthesis and Application in Catalysis." Catalysts 11, no. 8 (August 14, 2021): 972. http://dx.doi.org/10.3390/catal11080972.

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N-Heterocyclic carbene (NHC) ligands have become a privileged structural motif in modern homogenous and heterogeneous catalysis. The last two decades have brought a plethora of structurally and electronically diversified carbene ligands, enabling the development of cutting-edge transformations, especially in the area of carbon-carbon bond formation. Although most of these were accomplished with common imidazolylidene and imidazolinylidene ligands, the most challenging ones were only accessible with the acenaphthylene-derived N-heterocyclic carbene ligands bearing a π-extended system. Their superior σ-donor capabilities with simultaneous ease of modification of the rigid backbone enhance the catalytic activity and stability of their transition metal complexes, which makes BIAN-NHC (BIAN—bis(imino)acenaphthene) ligands an attractive tool for the development of challenging reactions. The present review summarizes synthetic efforts towards BIAN-NHC metal complexes bearing acenaphthylene subunits and their applications in modern catalysis, with special emphasis put on recently developed enantioselective processes.

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20

Iacopetta, Domenico, Jessica Ceramella, Camillo Rosano, Annaluisa Mariconda, Michele Pellegrino, Marco Sirignano, Carmela Saturnino, et al. "N-Heterocyclic Carbene-Gold(I) Complexes Targeting Actin Polymerization." Applied Sciences 11, no. 12 (June 18, 2021): 5626. http://dx.doi.org/10.3390/app11125626.

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Transition metal complexes are attracting attention because of their various chemical and biological properties. In particular, the NHC-gold complexes represent a productive field of research in medicinal chemistry, mostly as anticancer tools, displaying a broad range of targets. In addition to the already known biological targets, recently, an important activity in the organization of the cell cytoskeleton was discovered. In this paper, we demonstrated that two NHC-gold complexes (namely AuL4 and AuL7) possessing good anticancer activity and multi-target properties, as stated in our previous studies, play a major role in regulating the actin polymerization, by the means of in silico and in vitro assays. Using immunofluorescence and direct enzymatic assays, we proved that both the complexes inhibited the actin polymerization reaction without promoting the depolymerization of actin filaments. Our outcomes may contribute toward deepening the knowledge of NHC-gold complexes, with the objective of producing more effective and safer drugs for treating cancer diseases.

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21

Bertini, Simone, and Martin Albrecht. "O-Functionalised NHC Ligands for Efficient Nickel-catalysed C–O Hydrosilylation." CHIMIA International Journal for Chemistry 74, no. 6 (June 24, 2020): 483–88. http://dx.doi.org/10.2533/chimia.2020.483.

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A series of C,O-bidentate chelating mesoionic carbene nickel(ii) complexes [Ni(NHC^PhO)2] (NHC = imidazolylidene or triazolylidene) were applied for hydrosilylation of carbonyl groups. The catalytic system is selective towards aldehyde reduction and tolerant to electron-donating and -withdrawing group substituents. Stoichiometric experiments in the presence of different silanes lends support to a metal–ligand cooperative activation of the Si–H bond. Catalytic performance of the nickel complexes is dependent on the triazolylidene substituents. Butyl-substituted triazolylidene ligands impart turnover numbers up to 7,400 and turnover frequencies of almost 30,000 h-1, identifying this complex as one of the best-performing nickel catalysts for hydrosilylation and demonstrating the outstanding potential of O-functionalised NHC ligands in combination with first-row transition metals.

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22

Schaper, Lars-Arne, Sebastian J. Hock, Wolfgang A. Herrmann, and Fritz E. Kuehn. "ChemInform Abstract: Synthesis and Application of Water-Soluble NHC Transition-Metal Complexes." ChemInform 44, no. 14 (March 20, 2013): no. http://dx.doi.org/10.1002/chin.201314253.

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23

Sureshkumar, Devarajulu, Venkataraman Ganesh, Naoya Kumagai, and Masakatsu Shibasaki. "Direct Catalytic Addition of Alkylnitriles to Aldehydes by Transition-Metal/NHC Complexes." Chemistry - A European Journal 20, no. 48 (September 22, 2014): 15723–26. http://dx.doi.org/10.1002/chem.201404808.

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24

Sureshkumar, Devarajulu, Venkataraman Ganesh, Naoya Kumagai, and Masakatsu Shibasaki. "Direct Catalytic Addition of Alkylnitriles to Aldehydes by Transition-Metal/NHC Complexes." Chemistry - A European Journal 20, no. 48 (October 5, 2014): 15641. http://dx.doi.org/10.1002/chem.201405327.

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25

Hadlington, Terrance J., Tibor Szilvási, and Matthias Driess. "Metal nitrene-like reactivity of a SiN bond towards CO2." Chemical Communications 54, no. 67 (2018): 9352–55. http://dx.doi.org/10.1039/c8cc05238g.

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The unusual reactivity of the SiN bond in metallo-iminosilane [DippN = Si(OSiMe₃)Ni(Cl)(NHC)₂]1towards CO₂and cyclohexyl isocyanate (CyNCO) is reported;1reacts with two molar equiv. of CO₂to give the [2+2+2] cycloaddition product3with complete scission of the σ- and π-Si–N bonds, akin to transition-metal nitrene complexes.

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26

Schulte to Brinke, Christian, and F. Ekkehardt Hahn. "Synthesis of a flexible macrocyclic tetraimidazolium salt–precursor for a tetracarbene ligand with metal dependent coordination modes." Dalton Transactions 44, no. 32 (2015): 14315–22. http://dx.doi.org/10.1039/c5dt02115d.

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The flexibly bridged macrocyclic tetra-NHC ligand 4 reacts with d⁸ transition metal ions to yield mononuclear complexes of type [M(4)](PF₆)₂ (M = Ni, Pd, Pt) while reaction with Ag⁺ yields the tetranuclear sandwich-type octacarbene complex [Ag₄(4)₂](PF₆)₄.

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27

Wang, Wan-Qiang, Hua Cheng, Ye Yuan, Yu-Qing He, Hua-Jing Wang, Zhi-Qin Wang, Wei Sang, Cheng Chen, and Francis Verpoort. "Highly Efficient N-Heterocyclic Carbene/Ruthenium Catalytic Systems for the Acceptorless Dehydrogenation of Alcohols to Carboxylic Acids: Effects of Ancillary and Additional Ligands." Catalysts 10, no. 1 (December 19, 2019): 10. http://dx.doi.org/10.3390/catal10010010.

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The transition-metal-catalyzed alcohol dehydrogenation to carboxylic acids has been identified as an atom-economical and attractive process. Among various catalytic systems, Ru-based systems have been the most accessed and investigated ones. With our growing interest in the discovery of new Ru catalysts comprising N-heterocyclic carbene (NHC) ligands for the dehydrogenative reactions of alcohols, we designed and prepared five NHC/Ru complexes ([Ru]-1–[Ru]-5) bearing different ancillary NHC ligands. Moreover, the effects of ancillary and additional ligands on the alcohol dehydrogenation with KOH were thoroughly explored, followed by the screening of other parameters. Accordingly, a highly active catalytic system, which is composed of [Ru]-5 combined with an additional NHC precursor L5, was discovered, affording a variety of acid products in a highly efficient manner. Gratifyingly, an extremely low Ru loading (125 ppm) and the maximum TOF value until now (4800) were obtained.

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28

Vemula, Sandeep R., Michael R. Chhoun, and Gregory R. Cook. "Well-Defined Pre-Catalysts in Amide and Ester Bond Activation." Molecules 24, no. 2 (January 9, 2019): 215. http://dx.doi.org/10.3390/molecules24020215.

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Over the past few decades, transition metal catalysis has witnessed a rapid and extensive development. The discovery and development of cross-coupling reactions is considered to be one of the most important advancements in the field of organic synthesis. The design and synthesis of well-defined and bench-stable transition metal pre-catalysts provide a significant improvement over the current catalytic systems in cross-coupling reactions, avoiding excess use of expensive ligands and harsh conditions for the synthesis of pharmaceuticals, agrochemicals and materials. Among various well-defined pre-catalysts, the use of Pd(II)-NHC, particularly, provided new avenues to expand the scope of cross-coupling reactions incorporating unreactive electrophiles, such as amides and esters. The strong σ-donation and tunable steric bulk of NHC ligands in Pd-NHC complexes facilitate oxidative addition and reductive elimination steps enabling the cross-coupling of broad range of amides and esters using facile conditions contrary to the arduous conditions employed under traditional catalytic conditions. Owing to the favorable catalytic activity of Pd-NHC catalysts, a tremendous progress was made in their utilization for cross-coupling reactions via selective acyl C–X (X=N, O) bond cleavage. This review highlights the recent advances made in the utilization of well-defined pre-catalysts for C–C and C–N bond forming reactions via selective amide and ester bond cleavage.

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29

Pisanò, Gianmarco, and Catherine S. J. Cazin. "General Mechanochemical Synthetic Protocol to Late Transition Metal–NHC (N-Heterocyclic Carbene) Complexes." ACS Sustainable Chemistry & Engineering 9, no. 29 (July 12, 2021): 9625–31. http://dx.doi.org/10.1021/acssuschemeng.1c00556.

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30

Mendoza-Espinosa, Daniel, Alejandro Alvarez-Hernández, Deyanira Angeles-Beltrán, Guillermo E. Negrón-Silva, Oscar R. Suárez-Castillo, and José M. Vásquez-Pérez. "Bridged N-Heterocyclic/Mesoionic (NHC/MIC) Heterodicarbenes as Ligands for Transition Metal Complexes." Inorganic Chemistry 56, no. 4 (February 3, 2017): 2092–99. http://dx.doi.org/10.1021/acs.inorgchem.6b02778.

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31

Buchspies, Jonathan, Md Mahbubur Rahman, and Michal Szostak. "Transamidation of Amides and Amidation of Esters by Selective N–C(O)/O–C(O) Cleavage Mediated by Air- and Moisture-Stable Half-Sandwich Nickel(II)–NHC Complexes." Molecules 26, no. 1 (January 2, 2021): 188. http://dx.doi.org/10.3390/molecules26010188.

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The formation of amide bonds represents one of the most fundamental processes in organic synthesis. Transition-metal-catalyzed activation of acyclic twisted amides has emerged as an increasingly powerful platform in synthesis. Herein, we report the transamidation of N-activated twisted amides by selective N–C(O) cleavage mediated by air- and moisture-stable half-sandwich Ni(II)–NHC (NHC = N-heterocyclic carbenes) complexes. We demonstrate that the readily available cyclopentadienyl complex, [CpNi(IPr)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), promotes highly selective transamidation of the N–C(O) bond in twisted N-Boc amides with non-nucleophilic anilines. The reaction provides access to secondary anilides via the non-conventional amide bond-forming pathway. Furthermore, the amidation of activated phenolic and unactivated methyl esters mediated by [CpNi(IPr)Cl] is reported. This study sets the stage for the broad utilization of well-defined, air- and moisture-stable Ni(II)–NHC complexes in catalytic amide bond-forming protocols by unconventional C(acyl)–N and C(acyl)–O bond cleavage reactions.

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32

Sureshkumar, Devarajulu, Venkataraman Ganesh, Naoya Kumagai, and Masakatsu Shibasaki. "ChemInform Abstract: Direct Catalytic Addition of Alkylnitriles to Aldehydes by Transition-Metal/NHC Complexes." ChemInform 46, no. 17 (April 2015): no. http://dx.doi.org/10.1002/chin.201517076.

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33

Liu, Dongmei, Zaozao Qiu, Hoi-Shan Chan, and Zuowei Xie. "Synthesis, structural characterization, and reactivity of late transition-metal complexes bearing linked cyclopentadienyl–carboranyl ligands." Canadian Journal of Chemistry 90, no. 1 (January 2012): 108–17. http://dx.doi.org/10.1139/v11-115.

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Late transition-metal complexes bearing linked cyclopentadienyl/indenyl–carboranyl ligands were synthesized and their reactivities were examined. Reaction of Li2[Me2C(L)(C2B10H10)] (L = C5H4, C9H6, Me2NCH2CH2C5H3) with MCl2(PPh3)2 in Et2O afforded [η5:σ-Me2C(C5H4)(C2B10H10)]M(PPh3) (M = Co (4), Ni (5)), [η5:σ-Me2C(C9H6)(C2B10H10)]M(PPh3) (M = Co (6), Ni (7)), and [η5:σ-Me2C(Me2NCH2CH2C5H3)(C2B10H10)]Ni(PPh3) (8). Treatment of 4 or 5 with 2,6-dimethylphenylisocyanide, N-heterocyclic carbene (NHC), PCy3, or 1,2-bis(diphenylphosphino)ethane (dppe) gave the corresponding PPh3 displacement complexes [η5:σ-Me2C(C5H4)(C2B10H10)]M(2,6-Me2C6H3NC) (M = Co (9), Ni (10)), [η5:σ-Me2C(C5H4)(C2B10H10)]M[1,3-(2,6-i-Pr2C6H3)2C3N2H2] (M = Co (11), Ni (12)), [η5:σ-Me2C(C5H4)(C2B10H10)]Ni(PCy3) (13), or {[η5:σ-Me2C(C5H4)(C2B10H10)]Co}2(dppe) (14), respectively. These complexes were characterized by various spectroscopic techniques and elemental analyses. The molecular structures of 4–14 were further confirmed by single-crystal X-ray analyses.

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34

Chen, Cheng, Yang Miao, Kimmy De Winter, Hua-Jing Wang, Patrick Demeyere, Ye Yuan, and Francis Verpoort. "Ruthenium-Based Catalytic Systems Incorporating a Labile Cyclooctadiene Ligand with N-Heterocyclic Carbene Precursors for the Atom-Economic Alcohol Amidation Using Amines." Molecules 23, no. 10 (September 20, 2018): 2413. http://dx.doi.org/10.3390/molecules23102413.

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Transition-metal-catalyzed amide-bond formation from alcohols and amines is an atom-economic and eco-friendly route. Herein, we identified a highly active in situ N-heterocyclic carbene (NHC)/ruthenium (Ru) catalytic system for this amide synthesis. Various substrates, including sterically hindered ones, could be directly transformed into the corresponding amides with the catalyst loading as low as 0.25 mol.%. In this system, we replaced the p-cymene ligand of the Ru source with a relatively labile cyclooctadiene (cod) ligand so as to more efficiently obtain the corresponding poly-carbene Ru species. Expectedly, the weaker cod ligand could be more easily substituted with multiple mono-NHC ligands. Further high-resolution mass spectrometry (HRMS) analyses revealed that two tetra-carbene complexes were probably generated from the in situ catalytic system.

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35

Bołt, Małgorzata, and Patrycja Żak. "Bulky NHC–Cobalt Complex-Catalyzed Highly Markovnikov-Selective Hydrosilylation of Alkynes." Catalysts 13, no. 3 (March 2, 2023): 510. http://dx.doi.org/10.3390/catal13030510.

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The hydrosilylation of alkynes is one of the most attractive and, at the same time, most challenging catalytic transformations, usually demanding the use of noble transition metals. We describe a catalytic system, based on cobalt(0) complex and bulky N-heterocyclic carbene (NHC) ligands, permitting the highly effective hydrosilylation of a broad scope of alkynes and silanes. The application of bulky NHC ligands allowed a decrease in the amount of cobalt necessary for an effective reaction run to 2.5 mol% and provided excellent selectivity towards challenging α-vinylsilanes. The developed method tolerates a number of substituted aryl, alkyl, and silyl acetylenes. Moreover, it is suitable for both tertiary and secondary silanes. Our findings confirm that steric hindrance around the metal center can effectively increase the activity of a catalyst and ensure better selectivity than those of analogous complexes bearing smaller ligands.

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36

Maishal, Tarun Kumar, Jean-Marie Basset, Malika Boualleg, Christophe Copéret, Laurent Veyre, and Chloé Thieuleux. "AgOC(CF3)3: an alternative and efficient reagent for preparing transition metal-NHC-carbene complexes." Dalton Transactions, no. 35 (2009): 6956. http://dx.doi.org/10.1039/b900136k.

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37

Romain, Charles, Stéphane Bellemin-Laponnaz, and Samuel Dagorne. "Recent progress on NHC-stabilized early transition metal (group 3–7) complexes: Synthesis and applications." Coordination Chemistry Reviews 422 (November 2020): 213411. http://dx.doi.org/10.1016/j.ccr.2020.213411.

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38

Altmann, Philipp J., Daniel T. Weiss, Christian Jandl, and Fritz E. Kühn. "Exploring Coordination Modes: Late Transition Metal Complexes with a Methylene-bridged Macrocyclic Tetra-NHC Ligand." Chemistry - An Asian Journal 11, no. 10 (April 26, 2016): 1597–605. http://dx.doi.org/10.1002/asia.201600198.

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39

Diao, Tianning, Qiao Lin, and Gregory Dawson. "Experimental Electrochemical Potentials of Nickel Complexes." Synlett 32, no. 16 (August 26, 2021): 1606–20. http://dx.doi.org/10.1055/s-0040-1719829.

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AbstractNickel-catalyzed cross-coupling and photoredox catalytic reactions has found widespread utilities in organic synthesis. Redox processes are key intermediate steps in many catalytic cycles. As a result, it is pertinent to measure and document the redox potentials of various nickel species as precatalysts, catalysts, and intermediates. The redox potentials of a transition-metal complex are governed by its oxidation state, ligand, and the solvent environment. This article tabulates experimentally measured redox potentials of nickel complexes supported on common ligands under various conditions. This review article serves as a versatile tool to help synthetic organic and organometallic chemists evaluate the feasibility and kinetics of redox events occurring at the nickel center, when designing catalytic reactions and preparing nickel complexes.1 Introduction1.1 Scope1.2 Measurement of Formal Redox Potentials1.3 Redox Potentials in Nonaqueous Solution2 Redox Potentials of Nickel Complexes2.1 Redox Potentials of (Phosphine)Ni Complexes2.2 Redox Potentials of (Nitrogen)Ni Complexes2.3 Redox Potentials of (NHC)Ni Complexes

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40

Bittermann, Agnes, Eberhardt Herdtweck, Peter Härter, and Wolfgang A. Herrmann. "Rhodium(I), a Carbene-Transfer Transition-Metal Ion and a Synthetic Route to Symmetrical and Asymmetrical Substitutedtrans-RhCl(CO)(NHC)(NHC) Complexes." Organometallics 28, no. 24 (December 28, 2009): 6963–68. http://dx.doi.org/10.1021/om900785p.

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41

Pan, Yu, Xinxin Jiang, Yat-Ming So, Ching Tat To, and Gaohong He. "Recent Advances in Rare Earth Complexes Containing N-Heterocyclic Carbenes: Synthesis, Reactivity, and Applications in Polymerization." Catalysts 10, no. 1 (January 3, 2020): 71. http://dx.doi.org/10.3390/catal10010071.

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N-heterocyclic carbenes (NHCs) are ubiquitous ancillary ligands employed in metal-catalyzed homogeneous reactions and polymerization reactions. Of significance is the use of NHCs as the supporting ligand in second- and third-generation Grubbs catalysts for their application in olefin metathesis and ring-opening metathesis polymerization. While the applications of transition metal catalysts ligated with NHCs in polymerization chemistry are well-documented, the use of analogous rare earth (Ln = Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) catalysts in this area remains under-developed, despite the unique role of rare earth elements in regio- and stereo-specific (co)polymerization reactions. By using hetero-atom-tethered chelating NHCs and, more recently, the employment of other structurally related NHCs, NHC-ligated Ln complexes have proven to be promising and fruitful catalysts for selective polymerization reactions. This review summarizes the recent developments in the coordination chemistry of Ln complexes containing NHCs and their catalytic performance in polymerization.

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42

Rufino-Felipe, Ernesto, Rebeca Nayely Osorio-Yáñez, Moises Vera, Hugo Valdés, Lucero González-Sebastián, Adan Reyes-Sanchez, and David Morales-Morales. "Transition-metal complexes bearing chelating NHC Ligands. Catalytic activity in cross coupling reactions via C H activation." Polyhedron 204 (August 2021): 115220. http://dx.doi.org/10.1016/j.poly.2021.115220.

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43

Al-Romaizan, Abeer Nasser, Manoj Kumar Gangwar, Ankit Verma, Salem M. Bawaked, Tamer S. Saleh, Rahmah H. Al-Ammari, Ray J. Butcher, Ibadur Rahman Siddiqui, and Mohamed Mokhtar M. Mostafa. "Catalytic Acceptorless Dehydrogenation (CAD) of Secondary Benzylic Alcohols into Value-Added Ketones Using Pd(II)–NHC Complexes." Molecules 28, no. 13 (June 25, 2023): 4992. http://dx.doi.org/10.3390/molecules28134992.

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For the creation of adaptable carbonyl compounds in organic synthesis, the oxidation of alcohols is a crucial step. As a sustainable alternative to the harmful traditional oxidation processes, transition-metal catalysts have recently attracted a lot of interest in acceptorless dehydrogenation reactions of alcohols. Here, using well-defined, air-stable palladium(II)–NHC catalysts (A–F), we demonstrate an effective method for the catalytic acceptorless dehydrogenation (CAD) reaction of secondary benzylic alcohols to produce the corresponding ketones and molecular hydrogen (H2). Catalytic acceptorless dehydrogenation (CAD) has been successfully used to convert a variety of alcohols, including electron-rich/electron-poor aromatic secondary alcohols, heteroaromatic secondary alcohols, and aliphatic cyclic alcohols, into their corresponding value-added ketones while only releasing molecular hydrogen as a byproduct.

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44

Bull, James A., Michael G. Hutchings, Cristina Luján, and Peter Quayle. "New reactivity patterns of copper(I) and other transition metal NHC complexes: application to ATRC and related reactions." Tetrahedron Letters 49, no. 8 (February 2008): 1352–56. http://dx.doi.org/10.1016/j.tetlet.2007.12.084.

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45

Li, Zhi-Feng, Xiao-Ping Yang, Hui-Xue Li, and Guo-Fang Zuo. "Phosphorescent Modulation of Metallophilic Clusters and Recognition of Solvents through a Flexible Host-Guest Assembly: A Theoretical Investigation." Nanomaterials 8, no. 9 (September 2, 2018): 685. http://dx.doi.org/10.3390/nano8090685.

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MP2 (Second order approximation of Møller–Plesset perturbation theory) and DFT/TD-DFT (Density functional theory/Time-dependent_density_functional_theory) investigations have been performed on metallophilic nanomaterials of host clusters [Au(NHC)2]+⋅⋅⋅[M(CN)2]−⋅⋅⋅[Au(NHC)2]+ (NHC = N-heterocyclic carbene, M = Au, Ag) with high phosphorescence. The phosphorescence quantum yield order of clusters in the experiments was evidenced by their order of μS1/ΔES1−T1 values ( μ S 1 : S0 → S1 transition dipole, ∆ E S 1 − T 1 : splitting energy between the lowest-lying singlet S1 and the triplet excited state T1 states). The systematic variation of the guest solvents (S1: CH3OH, S2: CH3CH2OH, S3: H2O) are employed not only to illuminate their effect on the metallophilic interaction and phosphorescence but also as the probes to investigate the recognized capacity of the hosts. The simulations revealed that the metallophilic interactions are mainly electrostatic and the guests can subtly modulate the geometries, especially metallophilic Au⋅⋅⋅M distances of the hosts through mutual hydrogen bond interactions. The phosphorescence spectra of hosts are predicted to be blue-shifted under polar solvent and the excitation from HOMO (highest occupied molecular orbital) to LUMO (lowest unoccupied molecular orbital) was found to be responsible for the 3MLCT (triplet metal-to-ligand charge transfer) characters in the hosts and host-guest complexes. The results of investigation can be introduced as the clues for the design of promising blue-emitting phosphorescent and functional materials.

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46

Arnold, Polly L., Sergey Zlatogorsky, Natalie A. Jones, Christopher D. Carmichael, Stephen T. Liddle, Alexander J. Blake, and Claire Wilson. "Comparisons between Yttrium and Titanium N-Heterocyclic Carbene Complexes in the Search for Early Transition Metal NHC Backbonding Interactions." Inorganic Chemistry 47, no. 19 (October 6, 2008): 9042–49. http://dx.doi.org/10.1021/ic801046u.

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47

Sureshkumar, Devarajulu, Venkataraman Ganesh, Naoya Kumagai, and Masakatsu Shibasaki. "Cover Picture: Direct Catalytic Addition of Alkylnitriles to Aldehydes by Transition-Metal/NHC Complexes (Chem. Eur. J. 48/2014)." Chemistry - A European Journal 20, no. 48 (November 14, 2014): 15637. http://dx.doi.org/10.1002/chem.201490198.

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48

Piatek, Magdalena, Cillian O’Beirne, Zoe Beato, Matthias Tacke, and Kevin Kavanagh. "Pseudomonas aeruginosa and Staphylococcus aureus Display Differential Proteomic Responses to the Silver(I) Compound, SBC3." Antibiotics 12, no. 2 (February 8, 2023): 348. http://dx.doi.org/10.3390/antibiotics12020348.

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The urgent need to combat antibiotic resistance and develop novel antimicrobial therapies has triggered studies on novel metal-based formulations. N-heterocyclic carbene (NHC) complexes coordinate transition metals to generate a broad range of anticancer and/or antimicrobial agents, with ongoing efforts being made to enhance the lipophilicity and drug stability. The lead silver(I) acetate complex, 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene (NHC*) (SBC3), has previously demonstrated promising growth and biofilm-inhibiting properties. In this work, the responses of two structurally different bacteria to SBC3 using label-free quantitative proteomics were characterised. Multidrug-resistant Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) are associated with cystic fibrosis lung colonisation and chronic wound infections, respectively. SBC3 increased the abundance of alginate biosynthesis, the secretion system and drug detoxification proteins in P. aeruginosa, whilst a variety of pathways, including anaerobic respiration, twitching motility and ABC transport, were decreased in abundance. This contrasted the affected pathways in S. aureus, where increased DNA replication/repair and cell redox homeostasis and decreased protein synthesis, lipoylation and glucose metabolism were observed. Increased abundance of cell wall/membrane proteins was indicative of the structural damage induced by SBC3 in both bacteria. These findings show the potential broad applications of SBC3 in treating Gram-positive and Gram-negative bacteria.

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49

Feiters, Martin, A. Engwerda, B. van Weerdenburg, N. Eshuis, M. Tessari, A. Longo, D. Banerjee, C. Fonseca Guerra, F. M. Bickelhaupt, and F. Rutjes. "EXAFS and DFT studies on iridium catalysts for SABRE." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C958. http://dx.doi.org/10.1107/s205327331409041x.

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Since it was first developed, Nuclear Magnetic Resonance (NMR) has become a powerful analytical tool that is now used widely in the fields of chemistry, materials science, and medicine. One way to overcome the intrinsic insensitivity of NMR is to use hyperpolarization techniques to produce non-Boltzmann spin-state distributions. One of these techniques is Signal Amplification By Reversible Exchange (SABRE),[1] in which hyperpolarization is achieved by the temporary association of parahydrogen and a substrate in the coordination sphere of a transition metal. The polarization can be transferred from the parahydrogen-derived hydride ligands to the bound substrate via scalar coupling, followed by dissociation of the hyperpolarized substrate into the bulk solution. We have investigated the efficiency of various iridium NHC complexes with aliphatic and aromatic R groups as SABRE catalysts.[2] The used metal centre is a six-coordinate iridium N-heterocyclic carbene complex, with three substrates and two hydrides, in which the exchange rate of substrate and parahydrogen at the metal centre determines the efficiency of the hyperpolarization. As solvent molecules compete with pyridine for coordination to iridium, the sensitivity of SABRE can be enhanced by displacement of solvent molecules by cosubstrates, i.e. proton-poor ligands such as methyltriazole.[3] In this exchange process, several mixed iridium complexes can be considered to exist, which were not all observed by NMR. Therefore, Density Functional Theory (DFT) calculations were performed on these complexes to better understand this phenomenon. While NMR itself is the best source of information on protons and dynamic processes involved in SABRE, we have found that Extended X-ray Absorption Fine Structure (EXAFS) studies in organic solutions provide interesting complimentary information on the complexes involved.

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50

Wan, Kai Y., Alan J. Lough, and Robert H. Morris. "Transition Metal Complexes of an (S,S)-1,2-Diphenylethylamine-Functionalized N-Heterocyclic Carbene: A New Member of the Asymmetric NHC Ligand Family." Organometallics 35, no. 11 (May 3, 2016): 1604–12. http://dx.doi.org/10.1021/acs.organomet.6b00031.

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