Pyrene-Connected Tetraimidazolylidene Complexes of Iridium and Rhodium. Structural Features and Catalytic Applications

Abstract

A pyrene-connected tetra-imidazolium salt has been prepared starting from commercially available 1,3,6,8-tetrabromopyrene, and used as tetra-NHC precursor in the preparation of tetranuclear Rh­(I) and Ir­(I) complexes. The tetra-NHC ligand displays axial chirality upon coordination to the MCl­(cod) (M = Rh and Ir) fragments, giving rise to right- and left-handed helix conformations. The catalytic activity of the resulting complexes was studied in two relevant reactions that lead to the formation of five- and six-membered oxygen-containing heterocycles, namely, the cyclization of acetylenic carboxylic acid and the coupling of diphenyl­cyclo­propenone with substituted phenylacetylenes.

Unveiling Luminescent IrI and RhI N‐Heterocyclic Carbene Complexes: Structure, Photophysical Specifics, and Cellular Localization in the Endoplasmic Reticulum

“…This, in contrast, would lead to the formation of the more favorable structure at low temperatures. In the present case, this structure represents either of the two structures 8 a/b‐A or 8 a/b‐B , where the respective C3 or C5 proton is in a suitable position to form a halide bridge with the respective iodo ligand (see Figure 2), a feature that has been reported for complexes of a similar [M(COD)(NHC)X] type [48] …”

“…The ligands 4 and 7 were subsequently used for the synthesis of the respective Rh I and Ir I [M(COD)(NHC)X] complexes following a literature procedure for similar complexes with an NHC ligand [48] . To obtain the desired complexes, the imidazolium precursors 4 and 7 were treated with DIPEA ( N , N ‐diisopropylethylamine) and subsequently the respective Rh or Ir precursor [M(COD)Cl] 2 was added under inert conditions (Scheme 2).…”

Synthesis and Characterization of Poly‐NHC‐Derived Silver(I) Assemblies and Their Transformation into Poly‐Imidazolium Macrocycles

“…tetranuclear Rh I and Ir I complexes obtained from a related pyrene-bridged tetrakisimidazolylidene ligand displaying interesting structural and catalytic features. [16] The reaction of H 4 -2(PF 6 ) 4 with Ag 2 O, affords the tetranuclear cylinder-like assembly [7](PF 6 ) 4 in 74 % yield. Compound [7](PF 6 ) 4 was characterized by NMR spectroscopy and mass spectrometry.…”

“…1,3,6,8-Tetraimidazolylpyrene was prepared according to a reported method. [16] All other reagents were used as received from commercial suppliers. Anhydrous solvents were dried using a solvent purification system (SPS M BRAUN) or were distilled by standard procedures prior to use.…”

Recent advances in the catalytic applications of GO/rGO for green organic synthesis

“…In yet another study, Sabater et al [131] developed highly efficient catalyst by co-immobilizing Pd and Ru complexes with pyrene-tagged NHC ligands onto rGO surface and examined for its catalytic activity in the hydrodefluorination of a series of fluoroarenes with catalytic system recycled up to 12 times without the measurable loss of activity (Figure 3). Many organic transformations like the cyclization of acetylenic carboxylic acid and the coupling of diphenylcyclopropenone with substituted phenylacetylenes, hydrogenation of alkenes and alcohol oxidation have also been carried out using pyrene-tagged metal complexes supported on rGO with excellent recyclability [132,133].…”