Review
Chemistry, Multidisciplinary
Justus Diekamp, Thomas Seidensticker
Summary: The recycling of homogeneous catalysts in a homogeneous matrix is a challenging task for many reactions aiming for industrial applications. Although various synthetic approaches for recyclable homogeneous catalysts exist, a concise overview of catalyst modifications is lacking in the literature. This review aims to fill this gap by summarizing the existing synthesis pathways for polar, non-polar, fluorous, and molecular-weight-enlarged catalysts and examining their modular and late-stage approaches. Additionally, the potential for a generally applicable tag library to facilitate catalyst modifications for specific recycling strategies is explored.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Niklas F. Both, Anke Spannenberg, Haijun Jiao, Kathrin Junge, Matthias Beller
Summary: The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. Various aromatic and aliphatic esters were successfully hydrogenated at mild temperatures and low catalyst loadings using complexes 3 with KHBEt3 as additive, highlighting the efficiency of the novel catalytic system. Additionally, the versatility of the developed catalytic system was demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N-heteroarenes, and alkenes.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Review
Chemistry, Multidisciplinary
Zikun Wang, Nikolaos V. Tzouras, Steven P. Nolan, Xihe Bi
Summary: Silver N-heterocyclic carbenes (Ag-NHCs) have good biocompatibility and are widely used in medicine and coordination chemistry, but their coordination with silver can weaken the Lewis acidity of Ag(I), resulting in slow development as catalysts. Future opportunities lie in further research on the catalytic mechanisms of Ag-NHCs to enhance their catalytic activity.
TRENDS IN CHEMISTRY
(2021)
Article
Chemistry, Applied
Wenli Bai, Jian Sun, Dongyang Wang, Sheng-Di Bai, Liang Deng
Summary: This study investigates the catalytic performance of low-coordinate cobalt(0) N-heterocyclic carbene (NHC) complexes in the hydrosilylation reaction of alkynes, revealing the fine selectivity mechanism governed by the steric nature of the NHC ligand.
APPLIED ORGANOMETALLIC CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Louis Monsigny, Anna Kajetanowicz, Karol Grela
Summary: This review discusses a distinct class of ruthenium olefin metathesis catalysts with unsymmetrical N-heterocyclic carbene (uNHC) ligands, highlighting their advantages such as thermodynamic stability, chemical latency, selectivity, and compatibility with green solvents in specialized metathesis transformations. Despite being niche, uNHC complexes have the potential to be implemented in various industrial processes like valorization of Fischer-Tropsch olefin fractions, ethenolysis of renewable products, and modern pharmaceutical production.
Article
Chemistry, Multidisciplinary
Paul Zaby, Jan Blasius, Anna K. Mueller, Steven P. Nolan, Oldamur Holloczki
Summary: The formation mechanism of metal-N-heterocyclic carbene (NHC) complexes from imidazolium salts in the presence of weak bases was investigated through theoretical methods. Quantum chemical calculations revealed that both sodium acetate and trimethylamine facilitate complex formation. Molecular dynamics simulations showed that the ionic nature of the [AuCl2](-) and imidazolium ions, as well as the sodium acetate base, keep these species associated in the reaction mixture through ion pairing. The neutral amine, however, remains mostly separated from the other reaction partners, making it a significantly less effective base.
CHEMISTRY-A EUROPEAN JOURNAL
(2023)
Article
Chemistry, Organic
Bijin Lin, Xumu Zhang, Cong-Ying Zhou, Chi-Ming Che
Summary: An efficient method for synthesizing a PEGylated N-heterocyclic carbene(NHC)-gold(i) complex was described, which exhibited high reactivity and regio-selectivity in the cyclization of various alkynoic acids and cascade reaction of tryptamine and alkynoic acids in water. A systematic study of double cyclization of dialkynoic acids to construct spiro enol lactones was reported for the first time. Importantly, this water-soluble catalyst could be recycled seven times while maintaining good catalytic activity.
ORGANIC CHEMISTRY FRONTIERS
(2021)
Article
Chemistry, Multidisciplinary
David P. Tilly, William Cullen, Heng Zhong, Romain Jamagne, Inigo Vitorica-Yrezabal, Simon J. Webb
Summary: By investigating the effect of remotely induced changes in ligand folding, a potential pathway towards remote conformational control of organometallic catalysts has been discovered. The study on dynamic folding of Aib peptides revealed that the chiral conformational preference of N-terminal residues can be relayed to the axially chiral Rh(NHC) complex in the helical body.
CHEMISTRY-A EUROPEAN JOURNAL
(2022)
Article
Chemistry, Multidisciplinary
Mathis J. Benedikter, Janis V. Musso, Wolfgang Frey, Roman Schowner, Michael R. Buchmeiser
Summary: Despite their excellent selectivities and activities, Mo- and W-based catalysts for olefin metathesis have not been widely used due to their air sensitivity. The synthesized cationic-at-metal molybdenum and tungsten imido alkylidene NHC nitrile complexes are stable in air and can catalyze olefin metathesis reactions without prior activation. The presence of a nitrile ligand is crucial for their stability, while variations in imido and anionic ligands affect reactivities and stability.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Review
Chemistry, Multidisciplinary
Muneshwar Nandeshwar, Suman Mandal, Subramaniam Kuppuswamy, Ganesan Prabusankar
Summary: Sustainable noble metal-N-heterocyclic carbenes (NHC's) have gained significant attention in both the chemical industry and academic community due to environmental concerns and resource scarcity. The choice of catalyst supports plays a crucial role in heterogeneous catalysis, with graphene oxide (GO)/reduced graphene oxide (rGO) support showing great potential due to their larger surface area, inertness towards chemical transformations, and easy surface functionalization. Marrying metal-N-heterocyclic carbenes with GO/rGO support offers novel heterogeneous complexes with improved catalytic efficiency without sacrificing product selectivity, presenting opportunities for the chemical and pharmaceutical industry. However, limited examples of this approach are reported in the literature, highlighting the need for comprehensive reviews on metal-NHC synthesis on GO/rGO support and synthetic strategies for grafting M-NHC onto GO/rGO surface, as well as understanding the catalytic efficiency and mechanisms of non-covalent grafting methodology to design engineered catalysts for unexplored catalytic applications.
CHEMISTRY-AN ASIAN JOURNAL
(2023)
Review
Chemistry, Organic
Peibo Chen, Tingkai Xiong, Yingming Pan, Ying Liang
Summary: This review focuses on the application of N-heterocyclic carbene and related complexes in the chemical fixation of carbon dioxide. Various technologies, including carbene-metal catalytic system, carbene-free-metal catalytic system, and synergistic catalytic technology, are discussed. The possible role of carbene materials in chemical carbon fixation is explored by analyzing typical mechanisms.
ASIAN JOURNAL OF ORGANIC CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Hang Shen, Michael B. Larsen, Allison G. Roessler, Paul M. Zimmerman, Andrew J. Boydston
Summary: A new flex-activated mechanophore has been discovered, which releases an N-heterocyclic carbene (NHC) under mechanical load. This design demonstrates a promising first step towards flex-activated designs with downstream reactivities, allowing for iterative activation increases in the material through non-destructive compression cycles. The potential modularity of the mechanophore design is highlighted by the demonstration of two different NHC structures.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Chemistry, Organic
Zhen Li, Pengju Ji, Jin-Pei Cheng
Summary: A Brønsted basicity scale was established for nine representative N-heterocyclic olefins (NHOs) using an UV-visible spectroscopic method. The unsaturated NHOs were found to have stronger basicities compared to their N-heterocyclic carbene (NHC) analogues, while the basicities of the saturated NHOs were weaker. The nucleophilicity of the NHOs was also stronger than commonly used Lewis bases but weaker than their NHC analogues.
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Polymer Science
Rui Tan, Xiaochun Mu, Haiyang Wang, Yang Li
Summary: By using (i)Pr(2)Im as a Lewis base ligand, beta-H elimination reactions in propylene polymerization were suppressed, resulting in high molecular weight polypropylene and block copolymers. DFT calculations showed that the delocalized electrons in (i)Pr(2)Im could decrease the electro positivity of active sites, providing a convenient strategy for tuning their electronic properties.
Article
Chemistry, Multidisciplinary
Ludwig Zapf, Udo Radius, Maik Finze
Summary: The paper describes the synthesis of 1,3-bis(tricyanoborane)imidazolate anion and its derivatives, including a novel dianionic N-heterocyclic carbene. These compounds exhibit unique electronic and steric properties, making them promising ligands and building blocks for coordination chemistry.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
