<i>N</i>‐heterocyclic carbene complexes of Rh(I) and electronic effects on catalysts for 1,2‐addition of phenylboronic acid to aldehydes

Türkmen, Hayati; Çetınkaya, Bekır

doi:10.1002/aoc.1746

Cited by 9 publications

(4 citation statements)

References 49 publications

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“…The characteristic downfield signals for the NC H N + protons of the imidazol(in)ium salts disappeared in the 1 H NMR spectra of complexes 4a , 4b , 5a , 5b , 6a , 6b . These complexes exhibit 13 C chemical shifts and coupling constants that are comparable to those of other reported NHC–rhodium(I) complexes . 13 C chemical shifts showed that C carbene is substantially deshielded.…”

Section: Resultssupporting

confidence: 79%

“…Measurement of carbonyl stretching frequencies in [(NHC)Rh(X)(CO) 2 ] (X = halogen) complexes with infrared (IR) spectroscopy can be used to compare donor properties of NHC ligands, which are important for homogeneous catalysis . These electronic properties can be modified by changing the substituents at the 4,5‐position of imidazol(in)e backbone or by adding different substituents on nitrogen atoms of heterocycle …”

Section: Introductionmentioning

confidence: 99%

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Symmetric and dissymmetric N‐heterocyclic carbene rhodium(I) complexes: a comparative study of their catalytic activities in transfer hydrogenation reaction

Gülcemal

2012

Applied Organom Chemis

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Six new [RhBr(NHC)(cod)] (NHC = N-heterocyclic carbene; cod = 1,5-cyclooctadiene) type rhodium complexes (4-6) have been prepared by the reaction of [Rh(m-OMe)(cod)] 2 with a series of corresponding imidazoli(in)ium bromides (1-3) bearing mesityl (Mes) or 2,4,6-trimethylbenzyl (CH 2 Mes) substituents at N 1 and N 3 positions. They have been fully characterized by 1 H, 13 C and heteronuclear multiple quantum correlation NMR analyses, elemental analysis and mass spectroscopy. Complexes of type [(NHC)RhBr(CO) 2 ] (NHC = imidazol-2-ylidene) (7b-9b) were also synthesized to compare s-donor/p-acceptor strength of NHC ligands. Transfer hydrogenation (TH) reaction of acetophenone has been comparatively studied by using complexes 4-6 as catalysts. The symmetrically CH 2 Mes-substituted rhodium complex bearing a saturated NHC ligand (5a) showed the highest catalytic activity for TH reaction.

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Section: Resultssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Symmetric and dissymmetric N‐heterocyclic carbene rhodium(I) complexes: a comparative study of their catalytic activities in transfer hydrogenation reaction

Gülcemal

2012

Applied Organom Chemis

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“…First, we investigated the electron donation effect of ICy to the Rh nanocluster by XANES and XPS. Rh K -edge XANES (Figure S11) and Rh 3d XPS (Figure S12) spectra of ICy- r -Cr 0.19 Rh 0.06 CeO z showed similar structures to those of r -Cr 0.19 Rh 0.06 CeO z , indicating that ICy had a negligible effect on the electronic state of the Rh nanoclusters, which was different from previous reports of Pd nanoparticles and Rh complexes with coordinated NHC ligands. , Thus, ICy induced the catalytic activity in a different manner.…”

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confidence: 61%

Coordination-Induced Trigger for Activity: N-Heterocyclic Carbene-Decorated Ceria Catalysts Incorporating Cr and Rh with Activity Induction by Surface Adsorption Site Control

et al. 2022

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A coordination-induced trigger for catalytic activity is proposed on an N-heterocyclic carbene (NHC)-decorated ceria catalyst incorporating Cr and Rh (ICy-r-Cr0.19Rh0.06CeO z ). ICy-r-Cr0.19Rh0.06CeO z was prepared by grafting 1,3-dicyclohexylimidazol-2-ylidene (ICy) onto H2-reduced Cr0.19Rh0.06CeO z (r-Cr0.19Rh0.06CeO z ) surfaces, which went on to exhibit substantial catalytic activity for the 1,4-arylation of cyclohexenone with phenylboronic acid, whereas r-Cr0.19Rh0.06CeO z without ICy was inactive. FT-IR, Rh K-edge XAFS, XPS, and photoluminescence spectroscopy showed that the ICy carbene-coordinated Rh nanoclusters were the key active species. The coordination-induced trigger for catalytic activity on the ICy-bearing Rh nanoclusters could not be attributed to electronic donation from ICy to the Rh nanoclusters. DFT calculations suggested that ICy controlled the adsorption sites of the phenyl group on the Rh nanocluster to promote the C–C bond formation of the phenyl group and cyclohexenone.

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“…For an approximate evaluation of the electronic situation at a given metal center, metal bound carbonyl ligands have proved useful. Measuring of the carbonyl stretching frequencies of {M(CO)(NHC)} complexes allows an evaluation of the donor properties of NHC ligands, which is an important factor for homogeneous catalysis. − In order to evaluate the donor properties of the NHC ligand in 6 , for example, CO was bubbled through a solution of the complex in dichloromethane at ambient temperature to give complex 11 in good yield (Scheme ). The reaction resulted in a quantitative substitution of the COD ligand by two CO ligands.…”

Section: Resultsmentioning

confidence: 99%

Heterobimetallic Complexes Bridged by Imidazol{[4,5-f][1,10]-phenanthrolin}-2-ylidene: Synthesis and Catalytic Activity in Tandem Reactions

et al. 2019

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A series of monometallic complexes obtained by metalation of the phenanthrolin donor in 1, 3-dibutyl-1H-imidazol[4,5-f ][1,10]phenanthrolin}ium hexafluorophospate 1 (M = Pd 2, Ru 3, Ir 4) have been prepared. Subsequently, the imidazolium moiety of complexes 2−4 was metalated with M′, leading to the heterobimetallic phenanthroline/NHC complexes (M/M′ = Pd/Rh 5, Pd/Ir 6, Pd/ Ru 7, Ru/Pd 8, Ir/Pd 9) and the homobimetallic complex (M/M′ = Ir/Ir 10). The new complexes were characterized by elemental analysis, FTIR, UV−vis, and NMR spectroscopy. The molecular structures of the heterobimetallic complexes 5 and 6 were determined by X-ray diffraction studies. The catalytic activity of the heterobimetallic complexes 5−9 were tested in selected tandem reactions (dehalogenation/transfer hydrogenation and Suzuki−Miyaura coupling/transfer hydrogenation). It was found that the M/M′ heterobimetallic complexes display higher catalytic activities when compared to equimolar mixtures of the mononuclear complexes M and M′, thus indicating that an increase in the number of metal atoms in one complex leads to an increased activity in the tandem reactions.

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N‐heterocyclic carbene complexes of Rh(I) and electronic effects on catalysts for 1,2‐addition of phenylboronic acid to aldehydes

Abstract: 1,3-Diarylsubstituted imidazolinium salts, (NHC-H

Cited by 9 publications

References 49 publications

Symmetric and dissymmetric N‐heterocyclic carbene rhodium(I) complexes: a comparative study of their catalytic activities in transfer hydrogenation reaction

Symmetric and dissymmetric N‐heterocyclic carbene rhodium(I) complexes: a comparative study of their catalytic activities in transfer hydrogenation reaction

Coordination-Induced Trigger for Activity: N-Heterocyclic Carbene-Decorated Ceria Catalysts Incorporating Cr and Rh with Activity Induction by Surface Adsorption Site Control

Heterobimetallic Complexes Bridged by Imidazol{[4,5-f][1,10]-phenanthrolin}-2-ylidene: Synthesis and Catalytic Activity in Tandem Reactions

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