Pyridylidene Amines and Amides: Donor-Flexible Ligands for Catalysis

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(14), P. 9891 - 9904

Published: July 13, 2023

Ligands with flexible donor properties exhibit the unique ability to transition within continuum of neutral (L-type) and anionic (X-type) metal bonding in response their local electronic environment. This flexibility stabilizes transition-metal complexes unparalleled ways facilitates catalytic turnovers, especially when cycle features active center different oxidation states. Pyridylidene amines (PYEs) pyridylidene amides (PYAs) are examples nitrogen-based donor-flexible ligands. In past decade, application PYE PYA ligands catalysis has been growing, now include reactions such as hydrogen transfer reactions, water oxidation, CO2 utilization, among many others. Here we provide an overview these powerful ligands, including synthesis, properties, particular application─highlighting key ligand that impart high activity, well wide potential this rather underexplored system for diverse applications.

Language: Английский

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Mesoionic Imines (MIIs): Strong Donors and Versatile Ligands for Transition Metals and Main Group Substrates

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(25)

Published: March 14, 2022

We report the synthesis and reactivity of 1,2,3-triazolin-5-imine type mesoionic imines (MIIs). The MIIs are accessible by a base-mediated cycloaddition between substituted acetonitrile an aromatic azide, methylation established routes subsequent deprotonation. C=O-stretching frequencies in MII-CO2 -Rh(CO)2 Cl complexes were used to determine overall donor strength. stronger donors than N-heterocyclic (NHIs). excellent ligands for main group elements transition metals which they display substituent-induced fluorine-specific interactions undergo C-H activation. DFT calculations gave insights into frontier orbitals MIIs. predict relatively small HOMO-LUMO gap compared other related ligands. potentially able act as both π-donor π-acceptor This highlights potential exciting properties with huge future development.

Language: Английский

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Mesoionic N‐Heterocyclic Imines as Super Nucleophiles in Catalytic Couplings of Amides with CO₂

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(51)

Published: Oct. 19, 2022

An extended class of stable mesoionic N-heterocyclic imines (mNHIs), containing a highly polarized exocyclic imine moiety, were synthesized. The calculated proton affinities (PA) and experimentally determined Tolman electronic parameters (TEPs) reveal that these synthesized mNHIs have the highest basicity donor ability among NHIs reported so far. superior nucleophilicity newly designed was utilized in devising strategy to incorporate CO2 as bridging unit under reductive conditions couple inert primary amides. This further hetero-couplings between amide amine using . These hitherto unknown catalytic transformations introduced diversification various biologically active drug molecules metal-free conditions. underlying mechanism explored by performing series control experiments, characterizing key intermediates spectroscopic crystallographic techniques.

Language: Английский

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Redox‐Active Triazole‐Derived Mesoionic Imines with Ferrocenyl Substituents and their Metal Complexes: Directed Hydrogen‐Bonding, Unusual C−H Activation and Ion‐Pair Formation

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(35)

Published: April 18, 2024

Abstract We present herein the synthesis, characterization and complexation of ferrocenyl‐substituted MIIs (mesoionic imines) their metal complexes. In free MIIs, strong hydrogen bonding interactions are observed between imine‐N C−H bonds ferrocenyl substituents both in solid state solution. The influence this is so that with [IrCp*Cl 2 ] yields unique six‐membered iridacycles via C−H‐activation corresponding C−H‐site at Fc‐substituent not Ph‐substituent. This result contrast to previous reports which always a preferential activation phenyl substituent competitive reactions presence substituents. Ir complexes formed after in‐situ halide exchange reaction exist either [Ir−I] contact or as [Ir] + I − solvent separated ion‐pairs depending on polarity. iodide coordinated display drastically different physical properties. TEP (Tolman‐electronic‐parameter) these ligands was determined lines up previously reported MII‐ligands. redox properties were investigated by combination electrochemical spectroelectrochemical methods. show here how non‐covalent can have drastic chemical new class compounds.

Language: Английский

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An Anionic Mesoionic Carbene (anMIC) and its Transformation to Metallo MIC‐Boranes: Synthesis and Properties.

Angewandte Chemie International Edition, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 16, 2025

Abstract Neutral mesoionic carbenes (MICs) based on a 1,2,3‐triazole core have had strong impact various branches of chemistry such as homogeneous catalysis, electrocatalysis, and photochemistry/photophysics. We present here the first general synthesis anionic (anMICs, 2 ) borate backbone. The free anMIC is stable in solution under an inert atmosphere at low temperatures, can be stored for several weeks. Analysis donor properties shows that these anMICs are extremely σ‐donors, bypassing donors MICs, NHCs, NHCs N‐heterocyclic olefins. room temperature conversion leads to three equally interesting compound classes: amide‐coordinated borane MIC‐borane backbone ( 2BR 3 ), polymeric triazolide 1Li metallo‐MIC‐borane. metallo‐MIC‐borane 3Li precursor further compounds. Quantum chemical calculations been used elucidate mechanism transformation anMICs. thus introduce new categories compounds with potential different beyond.

Language: Английский

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An Anionic Mesoionic Carbene (anMIC) and its Transformation to Metallo MIC‐Boranes: Synthesis and Properties.

Angewandte Chemie, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 16, 2025

Abstract Neutrale mesoionische Carbene (MICs) basierend auf 1,2,3‐Triazolen haben einige Forschungsfelder wie der homogenen Katalyse, Elektrokatalyse und Photochemie/Photophysik nachhaltig vorangebracht. Mit dieser Arbeit präsentieren wir den ersten generellen Syntheseweg zu anionischen mesoionischen Carbenen (anMICs, 2 ) einem 1,2,3‐Triazol Borat‐Rückgrat. Das freie anMIC ist in Lösung unter inerten Bedingungen tiefen Temperaturen stabil kann für mehrere Wochen gelagert werden. Die Analyse Donor‐Eigenschaften zeigt die starke σ ‐Donor‐Fähigkeiten von anMICs, Donorqualitäten anderer starker Donoren etwa MICs, NHCs, anionischer NHCs oder N‐heterozyclischer Olefine übersteigt. Bei Raumtemperatur das drei andere, gleichwohl interessante Verbindungsklassen überführt werden: Ein Amid‐koordiniertes Boran MIC‐Boran ( 2BR 3 ), ein polymeres Triazolid 1Li metallo‐MIC‐Boran 3Li ). Dieses Metallo‐MIC‐Boran interessantes Synthon Synthese weiterer Amid‐koordinierter MIC‐Borane. Quantenchemische Rechnungen konnten herangezogen werden um diese Umwandlung anMICs näher beleuchten. Somit führen mit diesem Bericht neue Klassen mesoionischer Verbindungen großem Potential Teilgebieten Chemie benachbarten Disziplinen ein.

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Synthesis and Application of Amino‐1H‐1,2,3‐triazolium Salts

Asian Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 12(6)

Published: April 22, 2023

Abstract Herein, we developed a fluoride‐mediated nucleophilic aromatic amination of chloro‐1 H ‐1,2,3‐triazolium salts. Various functional groups were tolerated in this reaction, which enabled the synthesis functionalized amino‐1 In addition, investigated catalytic properties triazolium‐based N‐heterocyclic imines (NHIs) for cyanosilylation ketones. The substituent was found to play crucial role inducing high activity.

Language: Английский

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Sydnone Methides: Intermediates between Mesoionic Compounds and Mesoionic N‐Heterocyclic Olefins

European Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 26(18)

Published: April 17, 2023

Abstract Sydnone methides represent an almost unknown class of mesoionic compounds which possess exocyclic carbon substituents instead oxygen (sydnones) or nitrogen (sydnone imines) in the 5‐position a 1,2,3‐oxadiazolium ring. Unsubstituted 4‐positions give rise to generation anionic N‐heterocyclic carbenes by deprotonation. Preparations new sydnone are described here. They can be represented mesomeric structures with either carbanionic groups like −C(CN) 2 − , −C(CN)(COOMe) −C(CN)(CONH ) and −C(CN)(SO Me) corresponding C=C double bonds as common feature olefins. An X‐ray single structure analysis revealed length 140.7(3) pm bond solid state. From coalescence temperature (55 °C) determined series 13 C NMR experiments (150 MHz) at various temperatures, energy rotation 18.5 Kcal/mol was calculated for this bond. The signals carbenes, from 2‐mesityl‐substituted NHC proved stable up 10 °C, highly shifted upfield (δ carbene =157.9 ppm−160.5 ppm). reacted situ elemental selenium chlorophosphanes yield methide selenoethers after methylation 4‐phosphanylsydnone good excellent yields, respectively.

Language: Английский

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Investigations of the Influence of Two Pyridyl-Mesoionic Carbene Constitutional Isomers on the Electrochemical and Spectroelectrochemical Properties of Group 6 Metal Carbonyl Complexes

Inorganics, Journal Year: 2024, Volume and Issue: 12(2), P. 46 - 46

Published: Jan. 29, 2024

Metal complexes of mesoionic carbenes (MICs) the triazolylidene type and their derivatives have gained increasing attention in fields electrocatalysis photochemistry. The redox activity these metal is critical for applications both aforementioned fields. Easy accessibility modular synthesis open a wide field design ligands, such as bidentate ligands. combination an MIC with pyridyl unit ligand setup increases π acceptor properties ligands while retaining strong σ donor properties. analogy well-established 2,2′-bipyridine allows conclusions to be drawn about influence carbene (MIC) moiety tetracarbonyl group 6 cyclic voltammetry (spectro)electrochemistry (SEC). However, effects different connectivity pyridyl-MIC remain underexplored. Based on our previous studies, we present thorough investigation two constitutional isomers electrochemical UV-vis-NIR/IR/EPR spectroelectrochemical carbonyl complexes. Moreover, presented were investigated conversion CO2 using working electrodes, providing fundamental understanding electrode material precatalytic activation.

Language: Английский

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Amido‐Triazole Complexes, “Normal” Triazole‐Based Imines and Metallo‐Mesoionic Imines

ChemistryEurope, Journal Year: 2024, Volume and Issue: 3(1)

Published: Nov. 21, 2024

Abstract Mesoionic compounds are hugely popular in fields such as organic chemistry, organometallic chemistry and homogeneous catalysis. A new sub‐class the mesoionic imines (MIIs). We present here 5‐amino‐4‐pyridyl‐1,2,3‐triazole a versatile synthon for generating first examples of metallo‐MIIs. In this approach, we make use metallation at N‐pyridyl/N3‐triazole chelating pocket (instead quarternisation N3‐triazole) subsequent deprotonation to generate highly tunable These unprecedented metallo‐MIIs contain nucleophilic N‐donor site, electrophilic metal site. Apart from displaying strong directed H‐bonding interactions like their “classical” MII analogues, engage aromatic C−F activation well meta−C−H reactions. Facile synthesis homo heterodincuelar complexes which mixed coordinative saturation/unsaturation with these is presented. have also used precursor amido‐1,2,3‐triazole example “normal” (and not mesoionic) 1,2,3‐triazole based imine. Our results establish class that combine modularity click reactions, functionality fragments electronically ambivalent huge potential synthetic catalysis beyond.

Language: Английский

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