Tungsten Sulfido Alkylidene and Cationic Tungsten Sulfido Alkylidene N-Heterocyclic Carbene Complexes

High-oxidation-state group 6 metal alkylidenes have been dominated by imido and oxo ligands. Here, the first neutral tungsten sulfido alkylidene and cationic tungsten sulfido alkylidene N-heterocyclic carbene (NHC) complexes are presented. A synthesis route that entails the reaction of the corresponding tungsten alkylidyne precursors with H2S in tetrahydrofuran is outlined. Schrock-type complexes bearing chlorides as well as pentafluorophenoxide ligands were synthesized, while variations in the NHC (1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene (IMes), 1,3-dimesityl-4,5-dichloro-1,3-dihydro-2H-imidazol-2-ylidene (IMesCl2), and 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene (IDipp)) as well as in the anionic ligand (chloride, pentafluorophenoxide, and 2,6-diphenylphenoxide) were carried out for the cationic tungsten sulfido alkylidene NHC complexes. All complexes were tested in benchmark olefin metathesis reactions in which the cationic tungsten sulfido alkylidene NHC complexes showed high productivities. Atomic charges were calculated for several cationic tungsten sulfido alkylidene NHC complexes and compared to those of the analogous tungsten oxo and imido complexes. These calculations revealed charge distribution between the NHC and the metal, yet lower charges at the metal and less polarization of the metal alkylidene bond compared to their tungsten oxo and imido analogs.