Isolation\nand Characterization of Sulfonium-Ylide-Stabilized\nPalladium Carbenes

Isolable sulfonium-ylide-stabilized palladium carbene\ncomplexes\nwere synthesized through palladium(II)-induced cyclization of 1,2-alkynylarylsulfanes.\nX-ray crystallographic analysis characterized the maintenance of a\npalladium +2 oxidation state, with carbene-carbon–palladium\nbond lengths of 1.95 Å, indicating a partial double-bond character.\nThese endocyclic sulfonium ylide carbenes represent the first characterized\nand/or isolable examples of this ligand class; such groups were previously\nproposed as reaction intermediates during cyclization–carbonylation\nreactions. A variety of palladium(II) complexes bearing sulfonium-ylide\ncarbene ligands, with differing substituents, were synthesized, and\nthe structure and stability of these complexes in solution were analyzed\nby <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy, revealing reversibility\nand a stability dependence on substituents. The chirality of the sulfur\nheteroatom and the overall properties these ligands provide a potential\nelectronic and steric alternative to existing carbene ligands, which\ncould facilitate the future development of complementary metal-based\nreactivity.