C,N‐Palladacycles Containing N‐Heterocyclic Carbene and Azido Ligands – Effective Catalysts for Suzuki–Miyaura Cross‐Coupling Reactions

Abstract

AbstractAzido‐palladacycles containing C,N‐donor and N‐heterocyclic carbene ligands, [(C,N‐L)Pd(N3)(NHC)] [NHC = IPr; 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene], were prepared from (i) IPr and dinuclear PdII azides, [Pd(μ‐N3)(C,N‐Ln)]2 [C,N‐L1H = N,N′‐dimethylbenzylamine; C,N‐L2H = 2‐(2′‐thienyl)pyridine; C,N‐L3H = azobenzene; C,N‐L4H = 2‐(p‐tolyl)pyridine], or from (ii) NaN3 and mononuclear PdII chloride, [Pd(Cl)(IPr)(C,N‐Ln)], in aqueous solution. The structures of two of these products were determined by X‐ray crystallography. The palladacycles showed high catalytic efficiency toward activated and nonactivated aryl bromides (at room temperature) as well as aryl chlorides (at 80 °C) in Suzuki–Miyaura cross‐coupling reactions. In addition, coupling reactions of aryl chlorides using potassium aryl trifluoroborates instead of phenyl boronic acid gave good‐to‐excellent product yields.