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 Ag2O 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 Pd2C2N2 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.