Novel μ-η2:η2 coordination of a thiophenium cation

Abstract : Depending on the substituent (Tol or CF3) withdrawing power, reactions of the alkyne RCCH with the bis(acetonitrile) compound [Mo2(C5H5)2(μ-SCH 3)3-(CH3CN)2](BF4) (1) gave either the flyover metallacycle complex 4 or the thiophenium derivative 3. In 3 the thiophenium ligand shows a new μ-η2:η2 mode of coordination. A single-crystal structure of 3, the first complex with binding of thiophenium to a binuclear site, was obtained.