Solvent-controlled selective synthesis of a trans-configured benzimidazoline-2-ylidene palladium(II) complex and investigations of its Heck-type catalytic activity |
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Authors: | Han Vinh Huynh Joanne Hui Hui Ho Tiong Cheng Neo Lip Lin Koh |
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Affiliation: | Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 Singapore, Singapore |
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Abstract: | Reaction of N,N′-dimethylbenzimidazolyl iodide (A) with Pd(OAc)2 in DMSO gives selectively trans-bis(N,N′-dimethylbenzimidazoline-2-ylidene) palladium(II) diiodide (trans-2) in 77% yield. The selective formation of the trans-coordination isomer and thus the cis-trans rearrangement is driven by the insolubility of trans-2 in DMSO. X-ray single-crystal diffraction analysis and 13C NMR spectroscopy confirm the trans-geometry of the square planar Pd(II) complex. Catalytic studies show that cis-1 and trans-2 are highly efficient in the Mizoroki-Heck coupling reaction of aryl bromides and activated aryl chlorides both in DMF and [N(n-C4H9)4]Br as ionic liquid. The catalytic activities of Pd(II) complexes with N-heterocyclic carbene ligands derived from benzimidazole are comparable to their imidazole-derived analogues. |
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Keywords: | Palladium N-Heterocyclic carbene Homogeneous catalysis Heck coupling reaction |
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