ACID-CATALYZED C-H ACTIVATION OF ETHENE AND LINKING OF ALKYNES AT A DIRUTHENIUM CENTER

The Ru = Ru double-bonded mu-alkyne complexes [Ru2(mu-CO)(mu-RC2R)(eta-C5H5)2] react slowly or not at all with ethene and alkynes even under forcing conditions, but in the presence of acid C-H activation of ethene and alkyne-linking occur rapidly at room temperature to give di-mu-vinyl complexes [Ru2(CO)(mu-CR = CHR)(mu-CH = CH2)(eta-C5H5)2] and metallacyclopentadiene complexes [Ru2(CO)(mu-C4R4)(eta-C5H5)2] respectively; the acid catalysis is shown to proceed via the formation of a Ru = Ru triple-bonded mu-vinyl cation [Ru2(mu-CO)(mu-CR = CHR)(eta-C5H5)2]+.