NHC Backbone Configuration in Ruthenium-Catalyzed Olefin Metathesis

Paradiso, Veronica; Costabile, Chiara; Grisi, Fabia

doi:10.3390/molecules21010117

Cited by 27 publications

(12 citation statements)

References 64 publications

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“…The use of N‐heterocyclic carbenes (NHCs) as ligands for transition metals was first described in 1968 by Öfele and Wanzlick The development of metal–NHC complexes by Lappert in the early 1970s, and the isolation of the first stable free NHC by Arduengo and co‐workers in 1991, set the scene for an ever‐growing interest and advancement in the field of NHC chemistry. Since then, NHCs have been utilized extensively as ligands of transition‐metal complexes in organometallic chemistry and homogeneous catalysis …”

Section: Introductionmentioning

confidence: 99%

PEPPSI‐Type Palladium–NHC Complexes: Synthesis, Characterization, and Catalytic Activity in the Direct C5‐Arylation of 2‐Substituted Thiophene Derivatives with Aryl Halides

et al. 2017

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Six benzimidazolium salts, having two nitrogen atoms substituted by various alkyl groups, have been synthesized in high yields. The benzimidazolium salts readily converted into the corresponding PEPPSI-type palladium-NHC complexes (PEPPSI = pyridine-enhanced precatalyst preparation, stabilization, and initiation). The structures of all compounds have been characterized by 1 H NMR, 13 C NMR, and IR spectroscopy, as well as elemental analysis techniques, which support the proposed [a] Scheme 1. Pd-catalyzed direct C5-arylation of 2-substituted thiophenes with aryl halides.A number of palladium complexes, each with a single NHC ligand, have proven to be useful catalysts in cross-coupling reactions of aryl halides. [33,34] Among the most popular catalysts for such reactions are PEPPSI-type palladium-NHC complexes of the type [PdX 2 (NHC)(pyridine)], (X = halide, PEPPSI = pyridineenhanced precatalyst preparation, stabilization and ınitiation), which have gained real practical importance in numerous catalytic processes. [35] In 2006, Organ et al. reported [36] easily handled, air-and moisture-stable Pd-NHC complexes, created by using the PEPPSI method, which featured Pd II species bearing an NHC ligand, two halides, and a labile ligand such as 3chloropyridine. A lot of work has been done by many groups since 2006 on these types of complexes, [37] but only a few examples deal with the direct arylation of heteroarenes. [38] In view of the above information, and the growing interest of PEPPSItype palladium-NHC complexes in catalysis, we decided to investigate the catalytic activity of new members of this family in the direct C5-arylation of 2-substituted thiophenes.We now describe the synthesis and characterization of the benzimidazolium salts 2a-f as NHC species and their corre-Scheme 2. Synthesis of benzimidazolium salts 2a-f.

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Section: Introductionmentioning

confidence: 99%

PEPPSI‐Type Palladium–NHC Complexes: Synthesis, Characterization, and Catalytic Activity in the Direct C5‐Arylation of 2‐Substituted Thiophene Derivatives with Aryl Halides

et al. 2017

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“…Within this group, ruthenium-based complexes are among the most promising, with several lead compounds such as the NAMI-A [ 2 ], KP1019 [ 3 ] and RAPTA complexes [ 4 ]. Unlike biological activity, catalytical properties of ruthenium complexes have been firmly established and extensively used in organic chemistry, especially in olefin metathesis [ 5 , 6 , 7 , 8 , 9 ]. Our group has previously studied catalytically and biologically active complexes with various diketonates.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Structural Evaluation of Organo-Ruthenium Complexes with β-Diketonates

et al. 2017

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Four novel ruthenium organometallic complexes: [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)Cl] (1), [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)pta]PF6 (2), [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)Cl] (3) and [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)pta]PF6 (4) were synthesized and characterized by elemental analysis, infrared (IR), UV-Vis, NMR and mass spectroscopy and single-crystal X-ray diffraction. The crystal structures and spectroscopic data were compared to the previously published complexes [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-chloro-phenyl)-1,3-butanedione)Cl] (5) and [(η6-p-cymene)Ru(4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butanedione)pta]PF6 (6). The pairs of complexes 1 and 3 as well as 2 and 4 are isostructural, with the former crystallizing in triclinic P-1 and the latter in monoclinic P21/c. The ruthenium(II) ion is found in a pseudo-octahedral “piano-stool” geometry in all compounds. Bond lengths and angles are consistent with other complexes of this type. Complexes 2 and 4 exhibit some moderate dynamic disorder. The lack of hydrogen bonding and major π-π interactions means that most of intramolecular interactions are fairly weak and involve halogen atoms present. This was further confirmed by 1H-NMR spectra, where a significant difference is observed only on the ligand near the halogen atom, following an expected trend. The combined data show that the difference in any activity depends substantially on the type of the ligand′s substituted halogen atom.

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“…NHCs have been employed widely as very important ligands in many applications . Transition‐metal complexes of NHCs, which serve as catalysts for a variety of useful synthetic reactions in organometallic chemistry and homogeneous catalysis, have attracted much attention in recent years …”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7][8] Transition-metal complexes of NHCs, which serve as catalysts for a variety of useful synthetic reactions in organometallic chemistry and homogeneous catalysis, have attracted much attention in recent years. [9][10][11][12][13][14][15][16][17] Over the last few years, transition-metal complexes of NHCs have gained real practical importance as antimitochondrial, antimicrobial, and anticancer agents for medicinal applications. [18][19][20][21][22][23][24][25][26] Silver-NHC complexes are the most studied metal-NHC complexes because of their easy preparation.…”

Section: Introductionmentioning

confidence: 99%

Silver–N‐Heterocyclic Carbene Complexes: Synthesis, Characterization, and Antimicrobial Properties

Kaloğlu

Özdemır

et al. 2017

J Chinese Chemical Soc

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Six new silver complexes containing symmetrical N‐heterocyclic carbene (NHC) ligands were synthesized by the reaction of azolium salts with Ag2O in CH2Cl2 . These complexes were tested against Gram‐negative bacterial strains (Escherichia coli and Pseudomonas aeruginosa), Gram‐positive bacterial strains (Enterococcus faecalis and Staphylococcus aureus), and fungal strains (Candida albicans and Candida tropicalis), and all tested complexes showed good activity against the different microorganisms.

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NHC Backbone Configuration in Ruthenium-Catalyzed Olefin Metathesis

Cited by 27 publications

References 64 publications

PEPPSI‐Type Palladium–NHC Complexes: Synthesis, Characterization, and Catalytic Activity in the Direct C5‐Arylation of 2‐Substituted Thiophene Derivatives with Aryl Halides

PEPPSI‐Type Palladium–NHC Complexes: Synthesis, Characterization, and Catalytic Activity in the Direct C5‐Arylation of 2‐Substituted Thiophene Derivatives with Aryl Halides

Synthesis and Structural Evaluation of Organo-Ruthenium Complexes with β-Diketonates

Silver–N‐Heterocyclic Carbene Complexes: Synthesis, Characterization, and Antimicrobial Properties

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