NHC-Palladium(II) Mononuclear and Binuclear Complexes Containing Phenylene-Bridged Bis(thione) Ligands: Synthesis, Characterization, and Catalytic Activities

Abstract

A series of mono- and binuclear Pd­(II) complexes with N-heterocyclic carbene (NHC) and phenylene-bridged bis­(thione) (SCS) ligands were prepared and characterized by 1H and 13C NMR spectroscopy, IR, and mass spectrometry. The molecular structures of 1b, 2a, and 3b have been determined by the single-crystal X-ray diffraction method. The catalytic activities of the synthesized palladium complexes in the regioselective reduction of quinolines to the corresponding 1,2,3,4-tetrahydroquinolines were thoroughly investigated with ammonia–borane under mild reaction conditions. It is observed that the activities of the binuclear Pd­(NHC) complexes were higher than those of the corresponding mononuclear complexes under the same conditions.

General and Efficient Copper-Catalyzed Oxazaborolidine Complex in Transfer Hydrogenation of Isoquinolines under Mild Conditions

“…NMR spectra were recorded on a Bruker AVANCE III HD 600 spectrometer ( 1 H NMR: 600 MHz. 13 C NMR: 151 MHz) and Bruker AVANCE III HD 400 spectrometer ( 1 H NMR: 400 MHz.). Chemical shifts (δ) for 1 H NMR and 13 C NMR spectra are given in ppm relative to the internal standard tetramethylsilane (TMS).…”

“…13 C NMR: 151 MHz) and Bruker AVANCE III HD 400 spectrometer ( 1 H NMR: 400 MHz.). Chemical shifts (δ) for 1 H NMR and 13 C NMR spectra are given in ppm relative to the internal standard tetramethylsilane (TMS). The residual solvent signals were used as references for 1 H NMR and 13 C NMR spectra and the chemical shifts converted to the TMS scale (CDCl 3 : δ H = 7.26 ppm.…”

“…Direct hydrogenation of isoquinolines is one of most efficient, straightforward, and powerful methods. − However, hydrogenation of N -heterocycles is a difficult task, − especially for isoquinolines, probably because of their stable aromaticity, low reactivity, and strong coordination to the catalyst. For example, Beller and co-workers reported the cobalt catalyst for hydrogenation of quinoline with 3 mol % catalyst, 3 mol % tetradentate phosphine ligand, and 10 bar H 2 at 60 °C in 89% yield, while higher catalyst dosage (5 mol %) and temperature (150 °C) were required for isoquinoline .…”

Core‐Shell Nano‐Cobalt Catalyzed Chemoselective Reduction of N‐Heteroarenes with Ammonia Borane

“…At present, there are a few systems reported that can catalyze the transfer hydrogenation of quinoline derivatives with AB. [27][28][29][30][31][32][33] In homogeneous catalytic systems, several examples employing frustrated lewis pairs B(C 6 F 5 ) 3 , [27] Ni II -bis(pyrazolyl)pyridine, [28] cupric sulfate, [29] zirconium-hydride complex, [30] and Pd II complex [31] have been disclosed. Because of the chemically stable and easy to handle natures of heterogeneous catalysts, they have also been applied in the hydrogenation of quinolines with AB.…”

Synthesis, molecular docking, and biological evaluation of 5‐alkyl(aryl)‐2‐isobutylthiazole derivatives: As α‐amylase, α‐glucosidase, and protein kinase inhibitors

“…Çetinkaya and co-workers have reported Pd-NHC catalyzed C (sp 2 )ÀH bond activation reaction in 2005 [36]. Also, Doucet, Shao, Xu and Özdemir groups reported Pd-NHC complexes that showed important activity in C-H bond activation reactions [37][38][39][40][41][42][43][44][45][46][47]. C-H bond activation reactions of substituted thiazoles have been reported by various groups [35,47].…”