Synthesis of Imidazole-Based Functionalized Mesoionic Carbene Complexes of Palladium: Comparison of Donor Properties and Catalytic Activity toward Suzuki–Miyaura Coupling

Three different backbone-monofunctionalized
imidazolium salts have
been synthesized using the metal–halogen exchange procedure,
and their corresponding mesoionic carbene complexes with palladium
were prepared via oxidative addition without protection of the C2
position. The donor properties were evaluated with 31P
NMR spectroscopy of the respective palladium complexes. The catalytic
activity of these complexes toward Suzuki–Miyaura coupling
of aryl bromides was also explored. Also, in one case, a comparison
of donor properties was made with those of a “normal”
carbene with similar steric bulk.