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Title: Benzimidazolium-pyrazole-palladium(II) complexes: New and efficient catalysts for Suzuki, Heck and Sonogashira reactions
Authors: Li, F. 
Hor, T.S.A. 
Keywords: Cross-coupling
Hybrid ligands
N-heterocyclic carbenes
Water channel
X-ray structure determination
Issue Date: 6-Oct-2008
Citation: Li, F., Hor, T.S.A. (2008-10-06). Benzimidazolium-pyrazole-palladium(II) complexes: New and efficient catalysts for Suzuki, Heck and Sonogashira reactions. Advanced Synthesis and Catalysis 350 (14-15) : 2391-2400. ScholarBank@NUS Repository.
Abstract: Three unsymmetrical benzimidazoliumpyrazole N-N ligands 2-(1-propylbenzimidazolylmethyl)-3,5-di-R-pyrazole (R=H, Me, t-Bu) have been conveniently prepared and structurally analyzed. The solid lattice packingof the R=Me compound at 223 K reveals one-dimensional "zig-zag" water chains stabilized by organic molecular channels through N⋯H-O and O-H⋯O bonding. These hybrid ligands add to palladium(II) to give high yields of air-stable complexes that are fully characterized by NMR, ESI, and X-ray single-crystal crystallography. They are active Suzuki catalysts at room temperature towards cross-couplingof unactivated aryl bromides and 5- or 6-membered heteroaryl bromides with arylboronic acids with turnover frequencies (TOF) reachingas high as 60,000 h-1. Their catalytic efficiency is significantly better than that of the C-N carbene-imidazole analogue. These catalysts are also active in Heck and Sonogashira cross-coupling reactions of aryl bromides giving the desired products in good yields. These results suggested that these Pd(II) complexes with N-based hybrid ligands are versatile and efficient catalysts for different types of cross-couplingreactio ns under aerobic conditions. © 2008 Wiley-VCH VerlagGmbH & Co. KGaA.
Source Title: Advanced Synthesis and Catalysis
ISSN: 16154150
DOI: 10.1002/adsc.200800356
Appears in Collections:Staff Publications

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