Synthesis of dinuclear palladium complexes having two parallel isocyanide ligands, and their application as catalysts to pyrrole formation from tert-butylisocyanide and alkynes

Novel dinuclear palladium complexes having two isocyanide ligands were synthesized by using a binucleating ligand, N,N′-bis[2-(diphenylphsphino)phenyl]formamidinate (dpfam). The structure of [Pd2(μ-dpfam)(tert-BuNC)2]Cl was confirmed by X-ray analysis, showing that the Pd–Pd bond length of 2.5824(3) Å falls well within the range of those for known dipalladium complexes having the edge-sharing structure and two isocyanides coordinate to palladium in almost parallel and in close proximity. The dinuclear complex [Pd2(μ-dpfam)(tert-BuNC)2]PF6 served as catalyst for pyrrole formation from tert-butylisocyanide and various alkynes.