Template-Directed Synthesis of Palladium(II) Sulfonate-NHC Complexes and Catalytic Studies in Aqueous Mizoroki–Heck Reactions

Oxidation of easily accessible thiolato-functionalized dinuclear Pd­(II) NHC complexes 1–3 by Oxone gave rise to sulfonate-NHC complexes 4–6. This represents the first template-directed approach to NHC complexes bearing sulfonate functions, where the sulfur atoms undergo a six-electron oxidation, changing their oxidation states from −II to +IV. The catalytic activities of water-soluble 4–6 were also tested in aqueous Mizoroki–Heck reactions.