Palladium NHC complexes with benzimidazolium biphenyl ligands: Synthesis, structure, spectral characterization and their application in Suzuki-Miyaura reactions

Abstract

Synthesis of biphenyl appended benzimidazolium N-heterocyclic carbene (NHC) L1,2H2•X2 ligands, Silver benzimidazolium complex (L1Ag)·(PF6) 1 and Palladium complexes [L1Pd(H3C–CN)(Cl)]·(PF6) 2, [L1PdCl2] 3, [L1PdBr2] 4, [L2PdI2] 5 are reported. All complexes (1–5) are characterized by NMR, ESI-MS, elemental analysis and single crystal XRD. Complex 1 serves as an efficient NHC transfer agent for the preparation of complex 2. Treatment of complex 2 with AgPF6 in DCM solvent resulted in complex 3. Complexes 4 and 5 were prepared by direct metallation method. Complex 1 exists as monomer with Silver in slightly bent geometry. Complexes 2, 3, 4 and 5 are obtained with Palladium in distorted square-planar geometry. All Palladium complexes (2–5) are employed as catalysts in well known Suzuki-Miyaura cross-coupling reaction especially in water.