Palladium(II)‐N‐heterocyclic carbene complexes: synthesis, characterization and catalytic application

Abstract

N-Heterocyclic carbenes (NHCs) are of great importance and are powerful ligands for transition metals. A new series of sterically hindered benzimidazole-based NHC ligands (LHX) (2a-f), silver-NHC complexes (3a-f) and palladium-NHC complexes (4a-f) have been synthesized and characterized using appropriate spectroscopic techniques. Studies have focused on the development of a more efficient catalytic system for the Suzuki coupling reaction of aryl chlorides. Catalytic performance of Pd-NHC complexes and in situ prepared Pd(OAc) 2 /LHX catalysts has been investigated for the Suzuki cross-coupling reaction under mild reaction conditions in aqueous N,N-dimethylformamide (DMF). These complexes smoothly catalyzed the Suzuki-Miyaura reactions of electron-rich and electron-poor aryl chlorides.

Novel ruthenium(II)–N-heterocyclic carbene complexes; synthesis, characterization and catalytic application

“…3, 172.3, 176.4, 176.0 and 174.0 ppm, respectively. These results are consisting with known AgeNHC and RueNHC complexes [29,34].…”

Synthesis and catalytic applications of palladium N-heterocyclic carbene complexes as efficient pre-catalysts for Suzuki–Miyaura and Sonogashira coupling reactions

“…Complex bearing sterically bulky and electron-rich ligands exhibit enhanced catalytic activity in oxidative addition, and reductive elimination reactions that are key elemental steps of many catalytic reactions. [12][13][14][15][16][17] These unique features have contributed to make them indispensable ligands for transition metals in homogeneous and heterogeneous catalysis. [18][19][20][21][22][23][24][25][26][27][28][29][30] The cross-coupling reactions were successfully performed under homogeneous and heterogeneous catalyse conditions.…”

“…With K 2 CO 3 or t-BuOK as a base, DMF/water (1:1) mixture was a good solvent for the Suzuki reaction in the presence of the pyridine-containing palladium complex 3a (Table 1, entries 5, 6), whereas much better activities were obtained in toluene with complexes 2a and 4a using t-BuOK as a base ( Table 1). The low catalyst concentration causes to decrease the activity and the amount of product increases with the extended reaction time(table 1, entries [10][11][12][13][14][15]. With the complex 4a, low yield were obtained in the DMF/water mixture, which might be attributed to the low solubility of 4a due to containing triphenylphosphine ligand.…”

Cross coupling reactions catalyzed by (NHC)Pd(II) complexes

“…The sterically hindered NHC complexes (C73a-f ) smoothly catalyzed the reactions of electron-rich and electron-poor aryl chlorides under mild reaction conditions in aqueous DMF (Table 8, entries [28][29][30]. 107 Functionalizable Nheterocyclic carbene-triazole palladium complex (C74) was active in the Suzuki cross-coupling reaction (Table 8, entries 31 and 32).…”