Isolation of chloro-bridged arylpalladium complexes, [Pd2Ar2(μ-Cl)2(PR3)2], in palladium catalyzed C–C cross coupling reaction of triarylbismuth with arylhalides

The reaction of [Pd2Cl2(μ-Cl)2(PR3)2] with triarylbismuth in dichloromethane at room temperature afforded chloro-bridged arylpalladium complexes, [Pd2Ar2(μ-Cl)2(PR3)2] (Ar = Ph or 4-MeC6H4 (tol)) in 85–90% yield as a yellow crystalline powder. These complexes were characterized by elemental analysis and NMR spectroscopy. Molecular structures of [Pd2tol2(μ-Cl)2(PEt3)2] and [Pd2Ph2(μ-Cl)2(PMePh2)2] were established by single crystal X-ray crystallography. These complexes are centrosymmetric dimers with trans configuration. The C–C coupling reaction between triarylbismuth and an arylhalide in the presence of a base is catalyzed by [Pd2Cl2(μ-Cl)2(PR3)2]. The reactions proceed via an arylpalladium complex formed by transmetallation reaction between [Pd2Cl2(μ-Cl)2(PR3)2] and Ar3Bi. Probable reaction routes for C–C coupling have been discussed.