Reactions of Cp*RuCl(COD) with Alkynes: Isolation of Dinuclear Metallacyclopentatriene Complexes

The reactions of Cp*RuCl(COD) with alkynes in different solvents were investigated. Treatment of Cp*RuCl(COD) with phenylacetylene in benzene or dichloromethane gives the ruthenacyclopentatriene complex Cp*RuCl(2,5-Ph2C4H2) and free COD. In methanol, a formal [2+2+2] cycloaddition of the COD ligand with PhCCH occurred and the reaction produces a tricyclo[4.2.2.02,5]dec-7-ene (C6H5-C10H13) and its complex [Cp*Ru(η6-C6H5-C10H13)]Cl along with the dinuclear ruthenacyclopentatriene complex [Cp*RuCl(η2,η4,μ-2,5-Ph2C4H2)RuCp*]Cl. 3-Hexyne was found to be unreactive toward Cp*RuCl(COD) in benzene or dichloromethane at room temperature. In methanol, it reacts with Cp*RuCl(COD) to give a tricyclo[4.2.2.02,5]dec-7-ene (Et2-C10H12) and the dinuclear ruthenacyclopentatriene complex [Cp*RuCl(η2,η4,μ-C4Et4)RuCp*]Cl. 1-Hexyne was found to react with Cp*RuCl(COD) in C6D6, CD2Cl2, and diethyl ether to give the neutral dinuclear ruthenacyclopentadiene complex Cp*RuCl2(η2,η4,μ-C4H2Bu2)RuCp* along with free COD, while in methanol it gives a tricyclo[4.2.2.02,5]dec-7-ene (Bu-C10H13) and Cp*RuCl2(η2,η4,μ-C4H2Bu2)RuCp*.