Search results for "Carbene"
showing 10 items of 152 documents
Highly stable Cp*-Ir(III) complexes with N-heterocyclic carbene ligands as C-H activation catalysts for the deuteration of organic molecules.
2006
The preparation of a series of complexes of the type CpIrX2(NHC) provides effective catalysts for the H/D exchange of a wide range of organic molecules in methanol-d4. The reaction proceeds with higher yields under milder reaction conditions than previous CpIr systems reported thus far. For comparative purposes, we also studied the catalytic activity of CpIrCl2(PMe3) under the same reaction conditions. The molecular structures of two of the new CpIr(NHC) complexes are described.
N‐Heterocyclic Carbene Catalyzed Quadruple Domino Reactions: Asymmetric Synthesis of Cyclopenta[ c ]chromenones
2018
An N-heterocyclic carbene catalyzed domino sequence via α,β-unsaturated acyl azolium intermediates has been developed. This strategy provides a convenient enantioselective route to functionalized tricyclic coumarin derivatives and cyclopentanes. DFT studies and control experiments were performed to gain better insight into the reaction mechanism.
Reaction mechanism of regioisomerization in binuclear (diaminocarbene)PdII complexes
2021
Abstract A series of binuclear PdII carbene complexes were synthesized via the treatment of cis-[PdCl2(CNXyl)2] (1) with benzo-1,3-thiazol-2-amines (2–6) and structurally characterized. In every case the reaction leads to the mixture of two regioisomers, which are able to interconvert. The study of the regioisomerization of the binuclear diaminocarbene species showed that it is a first-order reaction, that is, it occurs intramolecularly, and was analyzed with the Hammett function. Electron-withdrawing substituents in the benzothiazole moiety of the complexes as well as increasing the solvent polarity accelerate the reaction. The solvent donor strength correlates less well with the isomeriza…
A Quantitative Model for Alkane Nucleophilicity Based on C−H Bond Structural/Topological Descriptors
2020
A first quantitative model for calculating the nucleophilicity of alkanes is described. A statistical treatment was applied to the analysis of the reactivity of 29 different alkane C−H bonds towards in situ generated metal carbene electrophiles. The correlation of the recently reported experimental reactivity with two different sets of descriptors comprising a total of 86 parameters was studied, resulting in the quantitative descriptor‐based alkane nucleophilicity (QDEAN) model. This model consists of an equation with only six structural/topological descriptors, and reproduces the relative reactivity of the alkane C−H bonds. This reactivity can be calculated from parameters emerging from th…
ATRP of Methacrylates Catalysed by Homo- and Heterobimetallic Ruthenium Complexes
2009
The catalytic activity of a series of ruthenium-based homo-and heterobimetallic complexes was determined by investigating the atom transfer radical polymerisation of methyl methacrylate. The complexes under investigation were [(arene)Ru(μ-Cl) 3 RuCl(C 2 H 4 )-(L)] (L = PCy 3 or a N-heterocyclic carbene ligand), [(p-cymene )-Ru(/l-Cl) 3 RuCl(=C=CHR)(PCy 3 )] (R = Ph or t-Bu), and [RuCl 2 -(p-cymene) {PCy 2 (CH2) 2 (n 5 -C 5 H 4 )TiX 2 (n 5 -C 5 H 5 )}] (X = Cl, F, and OBz). The catalytic activity of a variety of related [(p-cymene)-ClRu(μ-Cl) 2 Ru(O/\N)(=CHPh)] complexes (O^N is a Schiff base ligand) is also reported. The results clearly demonstrate that the ligands strongly affect the abili…
Reactivity of antitumor coinage metal-based N-heterocyclic carbene complexes with cysteine and selenocysteine protein sites
2021
Abstract The reaction of the antitumor M(I)-bis-N-heterocyclic carbene (M(I)-NHC) complexes, M = Cu, Ag, and Au, with their potential protein binding sites, i.e. cysteine and selenocysteine, was investigated by means of density functional theory approaches. Capped cysteine and selenocysteine were employed to better model the corresponding residues environment within peptide structures. By assuming the neutral or deprotonated form of the side chains of these amino acids and by considering the possible assistance of an external proton donor such as an adjacent acidic residue or the acidic component of the surrounding buffer environment, we devised five possible routes leading to the binding o…
Synthesis and Biological Evaluation of Organometallic Complexes Bearing Bis‐1,8‐naphthalimide Ligands
2018
Organometallic N-heterocyclic carbene (NHC) complexes with intercalating bis-naphthalimide ligands were prepared and evaluated biologically. Cytotoxic effects against tumor cells or bacteria were strongly ligand dependent with minor influence of the metal (Ag, Ru, Rh, Au) centers. Complex 8b with a rhodium(I) NHC moiety was studied in more detail for its DNA interacting properties in comparison to the metal free ligand. These studies showed a good DNA binding pattern with some preference for the telomeric quadruplex structure hTelo. Complex 8b was also shown to trigger additional coordinative binding to the DNA and therefore represents an useful tool compound with a mixed intercalative/coor…
CCDC 224282: Experimental Crystal Structure Determination
2004
Related Article: J.Vicente, M.-T.Chicote, M.D.Abrisqueta, M.M.Alvarez-Falcon, M.C.R.de Arellano, P.G.Jones|2003|Organometallics|22|4327|doi:10.1021/om030372r
CCDC 178876: Experimental Crystal Structure Determination
2004
Related Article: J.Vicente, M.-T.Chicote, M.D.Abrisqueta, M.M.Alvarez-Falcon, M.C.R.de Arellano, P.G.Jones|2003|Organometallics|22|4327|doi:10.1021/om030372r
CCDC 160388: Experimental Crystal Structure Determination
2002
Related Article: W.Uhl, F.Breher, A.Mbonimana, J.Gauss, D.Haase, A.Lutzen, W.Saak|2001|Eur.J.Inorg.Chem.||3059|doi:10.1002/1099-0682(200112)2001:12<3059::AID-EJIC3059>3.0.CO;2-Z