Dinuclear palladacyclic complexes derived from C-N cleavage of an imidazolium salt: Synthesis, structural characterization, and their uses for C-C coupling

Cleavage of a C-N bond of 3,6-(N-n-butylimidazolidenyl)pyridazine salt in its reactions with Ag(2)O and Pd(OAc)(2) was observed. Subsequent palladation of the resultant N-n-butylimidazole resulted in the isolation of two novel dinuclear palladacyclic complexes. Both complexes consist of a Pd(2)C(2)N(2) core with two palladium doubly bridged by anionic imidazoles in N,C5- or N,C2-coordination fashion. Accompanied with the C-N bond cleavage and palladation processes, addition of imidazole C-H to the C N bond of acetonitrile occurred in the reaction of Pd(OAc)(2) and 3,6-(N-n-butylimidazolidenyl)pyridazine. All compounds have been fully characterized by the usual spectroscopic techniques, and their X-ray molecular structures are described. The two palladacyclic complexes show good catalytic activities in Heck-Mizoroki and Suzuki coupling reactions of activated aryl bromides.