Browse
Submit Data
Databases
API
Help

Dataset Information

8 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Directed Design of a Au^I Complex with a Reduced Mesoionic Carbene Radical Ligand: Insights from 1,2,3-Triazolylidene Selenium Adducts and Extensive Electrochemical Investigations.

ABSTRACT: Carbene-based radicals are important for both fundamental and applied chemical research. Herein, extensive electrochemical investigations of nine different 1,2,3-triazolylidene selenium adducts are reported. It is found that the half-wave potentials of the first reduction of the selones correlate with their calculated LUMO levels and the LUMO levels of the corresponding triazolylidene-based mesoionic carbenes (MICs). Furthermore, unexpected quasi-reversibility of the reduction of two triazoline selones, exhibiting comparable reduction potentials, was discovered. Through UV/Vis/NIR and EPR spectroelectrochemical investigations supported by DFT calculations, the radical anion was unambiguously assigned to be triazoline centered. This electrochemical behavior was transferred to a triazolylidene-type MIC-gold phenyl complex resulting in a MIC-radical coordinated Au^I species. Apart from UV-Vis-NIR and EPR spectroelectrochemical investigations of the reduction, the reduced gold-coordinated MIC radical complex was also formed in situ in the bulk through chemical reduction. This is the first report of a monodentate triazolylidene-based MIC ligand that can be reduced to its anion radical in a metal complex. The results presented here provide design principles for stabilizing radicals based on MICs.

SUBMITTER: Beerhues J

PROVIDER: S-EPMC8252451 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Mesoionic Carbene Complexes of Uranium(IV) and Thorium(IV).

Project description:We report the synthesis and characterization of uranium(IV) and thorium(IV) mesoionic carbene complexes [An{N(SiMe3)2}2(CH2SiMe2NSiMe3){MIC}] (An = U, 4U and Th, 4Th; MIC = {CN(Me)C(Me)N(Me)CH}), which represent rare examples of actinide mesoionic carbene linkages and the first example of a thorium mesoionic carbene complex. Complexes 4U and 4Th were prepared via a C-H activation intramolecular cyclometallation reaction of actinide halides, with concomitant formal 1,4-proton migration of an N-heterocyclic olefin (NHO). Quantum chemical calculations suggest that the An-carbene bond comprises only a σ-component, in contrast to the uranium(III) analogue [U{N(SiMe3)2}3(MIC)] (1) where computational studies suggested that the 5f3 uranium(III) ion engages in a weak one-electron π-backbond to the MIC. This highlights the varying nature of actinide-MIC bonding as a function of actinide oxidation state. In solution, 4Th exists in equilibrium with the Th(IV) metallacycle [Th{N(SiMe3)2}2(CH2SiMe2NSiMe3)] (6Th) and free NHO (3). The thermodynamic parameters of this equilibrium were probed using variable-temperature NMR spectroscopy yielding an entropically favored but enthalpically endothermic process with an overall reaction free energy of ΔG 298.15K = 0.89 kcal mol-1. Energy decomposition analysis (EDA-NOCV) of the actinide-carbon bonds in 4U and 4Th reveals that the former is enthalpically stronger and more covalent than the latter, which accounts for the respective stabilities of these two complexes.

| S-EPMC9490841 | biostudies-literature

Towards new coordination modes of 1,2,3-triazolylidene: controlled by the nature of the 1st metalation in a heteroditopic bis-NHC ligand.

Project description:An unusual effect of the nature of the first metal coordination of a heteroditopic N-heterocyclic carbene ligand (L2) towards the coordination behavior of 1,2,3-tzNHC is explored. The first metal coordination at the ImNHC site (complexes 3 and 4) was noted to substantially influence the electronics of the 1,2,3-triazolium moiety leading to an unprecedented chemistry of this MIC donor. Along this line, the RhIII/IrIII-orthometalation in complexes 4 makes the triazolium C4-H more downfield shifted than C5-H, whereas a reverse trend, although to a lesser extent, is observed in the case of the non-chelated PdII-coordination. This difference in behavior assisted us to achieve the selective activation of triazole C4/C5 positions, not observed before, as supported by the isolation of the homo- and hetero-bimetallic complexes, 5, 6 and 7-9via C5- and C4-metalation, respectively. Furthermore, the %V bur calculations eliminate any considerable steric influence and the DFT studies strongly support the selectivity observed during bimetalation.

| S-EPMC9682892 | biostudies-literature

Cobaltocenylidene: A Mesoionic Metalloceno Carbene, Stabilized in a Gold(III) Complex.

Project description:Oxidative addition of cobaltoceniumdiazonium bis(hexafluoridophosphate) with (pseudo)halide aurates gave gold(III) complexes containing zwitterionic cobaltoceniumide as a ligand. Its selenium derivative, cobaltoceniumselenolate, was obtained by an electrophilic aromatic substitution reaction of iodocobaltocenium iodide with Na2 Se. Spectroscopic and structural data in combination with DFT calculations showed that this cobaltocenylidene species is a mesoionic carbene quite different from common N-heterocyclic carbenes. Its ligand properties (TEP, singlet-triplet gap, nucleophilicity, ?-acidity, Brønsted basicity) are in part comparable to those of cyclic (amino)(alkyl/aryl)carbenes. Electrochemistry data showed that the mesoionic cobaltoceniumides are more electron-rich than their parent ferrocenes. The reversible reduction of the tricyanido gold complex appears 50?mV negative of the cobaltocenium/cobaltocene couple, whereas that of the selenide derivative is shifted cathodically by 550?mV.

| S-EPMC5888181 | biostudies-literature

Crystalline 1H-1,2,3-triazol-5-ylidenes: new stable mesoionic carbenes (MICs).

Project description: Not available

| S-EPMC3131155 | biostudies-literature

Isomerization Reactions in Anionic Mesoionic Carbene-Borates and Control of Properties and Reactivities in the Resulting CoII Complexes through Agostic Interactions.

Project description:We present herein anionic borate-based bi-mesoionic carbene compounds of the 1,2,3-triazol-4-ylidene type that undergo C-N isomerization reactions. The isomerized compounds are excellent ligands for CoII centers. Strong agostic interactions with the "C-H"-groups of the cyclohexyl substituents result in an unusual low-spin square planar CoII complex, which is unreactive towards external substrates. Such agostic interactions are absent in the complex with phenyl substituents on the borate backbone. This complex displays a high-spin tetrahedral CoII center, which is reactive towards external substrates including dioxygen. To the best of our knowledge, this is also the first investigation of agostic interactions through single-crystal EPR spectroscopy. We conclusively show here that the structure and properties of these CoII complexes can be strongly influenced through interactions in the secondary coordination sphere. Additionally, we unravel a unique ligand rearrangement for these classes of anionic mesoionic carbene-based ligands.

| S-EPMC7839553 | biostudies-literature

Copper(I) complexes of mesoionic carbene: structural characterization and catalytic hydrosilylation reactions.

Project description:Two series of different Cu(I)-complexes of "click" derived mesoionic carbenes are reported. Halide complexes of the type (MIC)CuI (with MIC = 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (for 1b), 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (for 1c)) and cationic complexes of the general formula [Cu(MIC)2]X (with MIC =1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene, X = CuI2- (for 2á), 1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene, X = BF4- (for 2a), 1,4-(2,6-diisopropyl)phenyl-3-methyl-1,2,3-triazol-5-ylidene, X = BF4- (for 2b), 1-benzyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene, X = BF4- (for 2c)) have been prepared from CuI or [Cu(CH3CN)4](BF4) and the corresponding ligands, respectively. All complexes were characterized by elemental analysis and standard spectroscopic methods. Complexes 2á and 1b were studied by single-crystal X-ray diffraction analysis. Structural analysis revealed 2á to adopt a cationic form as [Cu(MIC)2](CuI2) and comparison of the NMR spectra of 2á and 2a confirmed this conformation in solution. In contrast, after crystallization complex 1b was found to adopt the desired neutral form. All complexes were tested for the reduction of cyclohexanone under hydrosilylation condition at elevated temperatures. These complexes were found to be efficient catalysts for this reaction. 2c was also found to catalyze this reaction at room temperature. Mechanistic studies have been carried out as well.

| S-EPMC6272443 | biostudies-literature

Gold(III)- versus gold(I)-induced cyclization: synthesis of six-membered mesoionic carbene and acyclic (aryl)(heteroaryl) carbene complexes.

Project description:The golden state: selective 5-exo- and 6-endo-cyclizations of an alkynyl benzothioamide have been achieved. The selectivity is controlled by the oxidation state of the gold precursor (+I or +III), yielding two new types of carbene ligand: an (aryl)(heteroaryl)carbene and a six-membered mesoionic carbene. Mes=2,4,6-trimethylphenyl.

| S-EPMC3712865 | biostudies-literature

Palladium Mesoionic Carbene Pre-catalyst for General Cross-Coupling Transformations in Deep Eutectic Solvents.

Project description:A strong ?-donor mesoionic carbene ligand has been synthesized and applied to four different palladium-catalyzed cross-coupling transformations, proving the catalyst/medium compatibility and the increased activity of this system over previous reports in Deep Eutectic Solvent medium. Some cross-coupling processes could be carried out at room temperature and using aryl chlorides as starting materials. The possible implementation of multistep synthesis in eutectic mixtures has also been explored. The presence of palladium nanoparticles in the reaction media has been evaluated and correlated to the observed activity.

| S-EPMC6819497 | biostudies-literature

N-Heterocyclic Carbene Adducts of Alkynyl Functionalized 1,3,2-Dithioborolanes.

Project description:Alkynyl functionalized boron compounds are versatile intermediates in the areas of medicinal chemistry, materials science, and optical materials. In particular, alkynyl boronate esters [R1-C≡C-B(OR2)2] are of interest since they provide reactivity at both the alkyne entity, with retention of the B-C bond or alkyne transfer to electrophilic substrates with scission of the latter. The boron atom is commonly well stabilized due to (i) the extraordinary strength of two B-O bonds, and (ii) the chelate effect exerted by a bifunctional alcohol. We reasoned that the replacement of a B-O for a B-S bond would lead to higher reactivity and post-functionalization in the resulting alkynyl boronate thioesters [R1-C≡C-B(S2X)]. Access to this poorly investigated class of compounds starts form chloro dithioborolane cyclo-Cl-B(S2C2H4) as a representative example. Whereas syntheses of three coordinate alkynyl boronate thioesters [R1-C≡C-B(S2X)] proved to be ineffective, the reactions of NHC-adducts (NHC = N-heterocyclic carbene) of cyclo-Cl-B(S2C2H4) afforded the alkyne substituted thioboronate esters in good yield. The products NHC-B(S2C2H4)(C≡C-R1) are remarkably stable towards water and air, which suggests their use as boron-based building blocks for applications akin to oxygen-based boronate esters.

| S-EPMC6539715 | biostudies-literature

AuICl-bound N-heterocyclic carbene ligands form MII4(LAuCl)6 integrally gilded cages.

Project description:The incorporation of an N-heterocyclic carbene (NHC) moiety into a self-assembled MII4L6 cage framework required the NHC first to be metallated with gold(i). Bimetallic cages could then be constructed using zinc(ii) and cadmium(ii) templates, showing weak luminescence. The cages were destroyed by the addition of further gold(i) in the form of AuI(2,4,6-trimethoxybenzonitrile)2SbF6, which caused the reversibly-formed cages to disassemble and controllably release the AuI-NHC subcomponent into solution. This release in turn induced the growth of gold nanoparticles. The rate of dianiline release could be tuned by capsule design or through the addition of chemical stimuli, with different release profiles giving rise to different nanoparticle morphologies.

| S-EPMC5512534 | biostudies-literature