Silver(I) and palladium(II) complexes of new pentamethylene-functionalized bis-imidazolium dication ligands and its application in Heck and Suzuki-Miyaura coupling reaction

Two new pentamethylene-functionalized bis-imidazolium dication ligands L-1 and L-2 (L-1 = 1,5-bis(4-(imidazolium-1-yl-phenol) pentane dibromide; L-2 = 1,5-bis(1-vinylimidazolium-1-yl) pentane dibromide) bearing IP (4-(imidazol-1-yl) phenol) and VI (1-vinylimidazole)-functionality have been prepared via the reaction of 1,5-dibromopentane with a substituted imidazole derivative. The bis-imidazolium dication ligands L-1 and L-2 on reaction with Ag2O in DCM: MeOH, followed by anion substitution with AgBF4 led to the formation of silver(I) complexes [Ag-2(C-P(CH2)(5)C-P)(2)][BF4](2) (PC(CH2)(5)C-P = 1,5-bis(4-(imidazolium-1-yl-phenol) pentane (1) and [Ag-2(C-V(CH2)(5)C-V)(2)][BF4](2) (C-V(CH2)(5)C-V = 1,5-bis(1-vinylimidazolium- 1-yl) pentane (2). Transmetalation of the bis-NHC ligand from [Ag-2(PC(CH2)(5)C-P)(2)][BF4](2) and [Ag-2(C-V(CH2)(5)C-V)(2)][BF4](2) by palladium(II) salt [PdCL2(CH3CN)(2)] in DMSO gave [PdCl(PC(CH2)(5)C-P) (CH3CN)] BF4 (3) and [PdCl(C-V(CH2)(5)CV)(CH3CN)] BF4 (4), respectively. The new ligands as well as their silver(I) and palladium(II) complexes have been characterized by elemental analysis, electronic, IR, H-1 and C-13 NMR, and FAB-MS spectroscopy. The molecular structure of the representative ligand L-1 has been determined by single crystal X-ray analysis. The palladium(II) NHC complexes 3 and 4 exhibited good activity in a model Heck and Suzuki-Miyaura coupling reaction. (C) 2016 Elsevier B.V. All rights reserved.