Activation of Terminal Alkynes at the Sulfur-Rich Bimetallic Site [MoIII2Cp2(μ-SMe)3]+: Alkyne−Vinylidene Conversion and C−S and C−C Couplings Promoted by Addition of Unsaturated Substrates (RC⋮CH, RN⋮C, SCS). Crystal Structures of μ-η1:η2-Vinylidene, μ-η1:η2-Acetylide, and μ-η1:η3-Vinyl−Thioether Compounds

Abstract

Reactions of the bis(nitrile) compound [Mo2Cp2(MeCN)2(μ-SMe)3](BF4) (1) with terminal alkynes in a 1:1 ratio in dichloromethane at room temperature led to the alkyne adduct [Mo2Cp2(μ-SMe)3(RCCH)](BF4) (2: R = Tol (2a), Ph (2b), CH3CCH2 (2c), nPr (2d), CO2Me (2e), CF3 (2f)). Compounds 2a−d were readily deprotonated with Et3N to give neutral acetylide derivatives [Mo2Cp2(μ-η1:η2-C⋮CR)(μ-SMe)3] (3). Protonation of 3 afforded exclusively the vinylidene complexes [Mo2Cp2(μ-η1:η2-CCHR)(μ-SMe)3](BF3) (4). Reaction of 1 with an excess of terminal alkyne RCCH in dichloromethane gave either the six-membered metallacycle compounds [Mo2Cp2(μ-η2:η4-CRCHCRCHSMe)(μ-SMe)2](BF4) (5) or the S-methylthiophenium derivatives [Mo2Cp2(μ-η2:η4-C4H2R2SMe)(μ-SMe)2](BF4) (6), depending on the nature of the R groups. Further reactions of the alkyne adducts 2 with isocyanide and carbon disulfide led to the vinyl−thioether complexes [Mo2Cp2(μ-η1:η3-CRCR‘-SMe)(μ-SMe)2(RNC)](BF4) (7, 8) and to their CS2 adducts [Mo2Cp2(S2C−CR‘CRSMe)(μ-...