25364-44-7Relevant articles and documents
Alkaline Earth Metal-Carbene Complexes with the Versatile Tridentate 2,6-Bis(3-mesitylimidazol-2-ylidene)pyridine Ligand
Koch, Alexander,Krieck, Sven,G?rls, Helmar,Westerhausen, Matthias
, p. 994 - 1000 (2017)
Diffusion of 2,6-bis(3-mesitylimidazol-2-ylidene)pyridine (CarMesPyCarMes, 2) into a solution of CaI2 in THF leads to microcrystalline [(CarMesPyCarMes)(thf)CaI2] (3), in one case containin
Catalytic Transfer of Magnetism Using a Neutral Iridium Phenoxide Complex
Ruddlesden, Amy J.,Mewis, Ryan E.,Green, Gary G. R.,Whitwood, Adrian C.,Duckett, Simon B.
, p. 2997 - 3006 (2015)
A novel neutral iridium carbene complex Ir(κC,O-L1)(COD) (1) [where COD = cyclooctadiene and L1 = 3-(2-methylene-4-nitrophenolate)-1-(2,4,6-trimethylphenyl)imidazolylidene] with a pendant alkoxide ligand has been prepared and characterized. It contains a strong Ir-O bond, and X-ray analysis reveals a distorted square planar structure. NMR spectroscopy reveals dynamic solution-state behavior commensurate with rapid seven-membered ring flipping. In CD2Cl2 solution, under hydrogen at low temperature, this complex dominates, although it exists in equilibrium with a reactive iridium dihydride cyclooctadiene complex. 1 reacts with pyridine and H2 to form neutral Ir(H)2(κC,O-L1)(py)2, which also exists in two conformers that differ according to the orientation of the seven-membered metallocycle, and while its Ir-O bond remains intact, the complex undergoes both pyridine and H2 exchange. As a consequence, when placed under para-hydrogen, efficient polarization transfer catalysis (PTC) is observed via the signal amplification by reversible exchange (SABRE) approach. Due to the neutral character of this catalyst, good hyperpolarization activity is shown in a wide range of solvents for a number of substrates. These observations reflect a dramatic improvement in solvent tolerance of SABRE over that reported for the best PTC precursor IrCl(IMes)(COD). For THF, the associated 1H NMR signal enhancement for the ortho proton signal of pyridine shows an increase of 600-fold at 298 K. The level of signal enhancement can be increased further through warming or varying the magnetic field experienced by the sample at the point of catalytic magnetization transfer. (Chemical Equation Presented).
Synthetic approaches to sterically hindered N-arylimidazoles through copper-catalyzed coupling reactions
Alcalde, Ermitas,Dinares, Immaculada,Rodriguez, Sandra,De Miguel, Cristina Garcia
, p. 1637 - 1643 (2005)
Optimization studies allowed the efficient synthesis of a simple structural motif based on meta-bis(1-imidazolyl)benzenes 1 through copper-catalyzed coupling of 1,3-diiodobenzene and imidazole under mild reaction conditions. This protocol was then used to prepare a representative sterically hindered N-arylimidazole 2a, the most common structural motif among N-heterocyclic carbenes (NHC). Having optimized the main variables governing CuI-catalyzed imidazole N-arylation, the first Ullmann-type synthesis of N-mesitylimidazole (2a) is reported. Moreover, the coupling between boronic acids as the aryl donor partners and either imidazole or benzimidazole was examined; in all cases the reactions proceeded in very low yield. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
Synthesis and characterization of novel Pd(II) complexes with chelating and non-chelating heterocyclic iminocarbene ligands
Froseth, Morten,Netland, Kjetil Andreas,Toernroos, Karl Wilhelm,Dhindsa, Ajaib,Tilset, Mats
, p. 1664 - 1674 (2005)
The imidazolium salts [3-R1-1-{2-Ar-imino)-2-R 2-ethyl}imidazolium] chloride (C-N; Ar = 2,6-iPr 2C6H3; R1/R2 = Me/Me (a), Me/Ph (b), Ph/Me (c), 2,4,6-Me3C6H2 (d), 2,6-iPr2C6H3 (e)) react with Ag 2O to give Ag(I) iminocarbene complexes (C-N)AgCl (4a-e) in which the iminocarbene ligand is bonded to Ag via the imidazoline-2-ylidene carbon atom. The solid-state structures of 4b and 4d were determined by X-ray crystallography and revealed the presence of monomeric (carbene)AgCl units with Z and E configurations at the imine C=N bonds, respectively. Carbene transfer to Pd occurs when compounds 4b-e are treated with (COD)PdCl2 to yield bis(carbene) complexes (C-N)2PdCl2 (6b-e) containing two κ1-C bonded iminocarbene moieties. NMR spectroscopic data indicated a trans coordination geometry at Pd. This conclusion was supported by an X-ray structure determination of 6b which clearly demonstrated the non-chelating nature of the iminocarbene ligand system. EXSY 1H NMR spectroscopy suggests that the non-chelating structures undergo E/Z isomerization at the imine C=N double bonds in solution. The preparative results contrast our earlier report that the reaction between 4a and (COD)PdCl 2 results in a chelating κ2-C,N bonded iminocarbene complex (C-N)PdCl2. The coordination mode and dynamic behavior of the iminocarbene ligand systems have been found to be dramatically affected by changes in the substitution pattern of the ligand system. Sterically unencumbered systems (a) favor the formation of κ2-C,N chelate structures containing one iminocarbene moiety per metal upon coordination at Pd(II); these complexes were demonstrated to engage in reversible, solvent-mediated chelate ring-opening reactions. Sterically encumbered systems (b-e) form non-chelating κ1-C iminocarbene Pd(II) complexes containing two iminocarbene ligands per metal. Transannular repulsions across the chelate ring are believed to be the origin of these structural differences. The Royal Society of Chemistry 2005.
Alkaline Stability of Low Oxophilicity Metallopolymer Anion-Exchange Membranes
Aggarwal, Kanika,Bsoul, Saja,Douglin, John C.,Li, Songlin,Dekel, Dario R.,Diesendruck, Charles E.
supporting information, (2022/01/11)
Anion-exchange membrane fuel cells (AEMFCs) are promising energy conversion devices due to their high efficiency. Nonetheless, AEMFC operation time is currently limited by the low chemical stability of their polymeric anion-exchange membranes. In recent years, metallopolymers, where the metal centers assume the ion transport function, have been proposed as a chemically stable alternative. Here we present a systematic study using a polymer backbone with side-chain N-heterocyclic carbene (NHC) ligands complexed to various metals with low oxophilicity, such as copper, zinc, nickel, and gold. The golden metallopolymer, using the metal with the lowest oxophilicity, demonstrates exceptional alkaline stability, far superior to state-of-the-art quaternary ammonium cations, as well as good in situ AEMFC results. These results demonstrate that judiciously designed metallopolymers may be superior to purely organic membranes and provides a scientific base for further developments in the field.
Expedient Synthesis of Bis(imidazolium) Dichloride Salts and Bis(NHC) Complexes from Imidazoles Using DMSO as a Key Polar Additive
Anders, Evan J.,Lindsay, Vincent N. G.,Penn, Kyle R.
supporting information, p. 3871 - 3875 (2021/12/13)
A general approach for the synthesis of bis(imidazolium) dichloride salts from imidazoles and dichloroalkanes is reported. Typical limitations of this reaction for the formation of methylene-bridged derivatives are addressed herein through the use of excess CH2Cl2 in the presence of DMSO as a polar cosolvent, significantly improving the conversion rates presumably via stabilization of the initial SN2 transition state. The method was also shown to be applicable to the formation of bis(pyridinium) dichloride salts from pyridine derivatives, and to the direct synthesis of metal-bis(NHC) complexes from imidazoles.
One pot tandem dual CC and CO bond reductions in the β-alkylation of secondary alcohols with primary alcohols by ruthenium complexes of amido and picolyl functionalized N-heterocyclic carbenes
Dey, Shreyata,Ghosh, Prasenjit,Prakasham, A. P.,Ta, Sabyasachi
supporting information, p. 15640 - 15654 (2021/11/30)
Two different classes of ruthenium complexes, namely, [1-mesityl-3-(2,6-Me2-phenylacetamido)-imidazol-2-ylidene]Ru(p-cymene)Cl (1c) and {[1-(pyridin-2-ylmethyl)-3-(2,6-Me2-phenyl)-imidazol-2-ylidene]Ru(p-cymene)Cl}Cl (2c), successfully catalyzed the one-pot tandem alcohol-alcohol coupling reactions of a variety of secondary and primary alcohols, in moderate to good yields of ca. 63-89%. The mechanistic investigation performed on two representative catalytic substrates, 1-phenylethanol and benzyl alcohol using the neutral ruthenium (1c) complex showed that the catalysis proceeded via a partially reduced CC hydrogenated carbonyl species, [PhCOCH2CH2Ph] (3′), to the fully reduced CO and CC hydrogenated secondary alcohol, [PhCH(OH)CH2CH2Ph] (3). Furthermore, the time dependent study showed that the major product of the catalysis modulated between (3′) and (3) during the catalysis run performed over an extended period of 120 hours. Finally, the practical utility of the alcohol-alcohol coupling reaction was demonstrated by preparing five different flavan derivatives (13-17) related to various bioactive flavonoid natural products, in a one-pot tandem fashion.
