Four bis-benzimidazolium salts, 1,4-bis[1'-(N-R-benzimidazoliumyl)methyl]-2,3,5,6-tetramethylbenzene 2X^- (L ¹ H ₂ ·(PF ₆ ) ₂ : R = ethyl, X = PF₆; L ² H ₂ ·Br ₂ : R = picolyl, X = Br; L ³ H ₂ ·Br ₂ : R = benzyl, X = Br; and L ⁴ H ₂ ·Br ₂ : R = allyl, X = Br), and their three N-heterocyclic carbene (NHC) Pd(II) and Ag(I) complexes, L ¹ Pd ₂ Cl ₄ (1), L ² Ag ₂ Br ₂ (2), and L ⁴ (AgBr) ₂ (3), as well as one anionic complex L ³ H ₂ ·(Ag ₄ Br ₈ ) _0.5 (4), have been synthesized and characterized. Complex 1 adopts a funnel-like type of structure, complex 2 adopts a cyclic structure, and complex 3 is an open structure. In the crystal packing of 1-4, one-dimensional polymeric chains and two-dimensional supramolecular layers are formed via intermolecular weak interactions, including hydrogen bonds, π-π interactions, and C-H···π contacts. The catalytic activities of NHC Pd(II) complex 1 in three types of C-C coupling reactions (Suzuki-Miyaura, Heck-Mizoroki, and Sonogashira reactions) were studied. The results show that this catalytic system is efficient for these C-C coupling reactions.

Shao-Cong Yu

Publications