Fulvene–Ruthenium and Cp–Ruthenium Complexes via [2 + 2 + 1] Cyclotrimerization of Phenylacetylene with [RuCl(Tp)(1,5-cod)]

The complex [RuCl(Tp)­(1,5-cod)], which bears the labile 1,5-cod ligand, was prepared from a high-yielding route involving the reaction of [RuCl2­(1,5-cod)­(CH3CN)2] with KTp (Tp = HB(pz)3). The reaction of [RuCl(Tp)­(1,5-cod)] with phenylacetylene in either ethanol or methanol gave anti-Markovnikov alkoxide-adduct complexes [Ru(Tp)­(η6-C5H2Ph2-CH(Ph)R)] (R = OMe, OEt). These adducts were formed by [2 + 2 + 1] cyclotrimerization reactions of phenylacetylene mediated by the precursor complex, [RuCl(Tp)­(1,5-cod)]. The ruthenium(II)–fulvene complex, [Ru(Tp)­(η6-C5H2Ph2-CH(Ph))]+, involved in these transformations was successfully isolated in the presence of NH4PF6. These complexes were fully characterized by 1H NMR, 13C NMR, DEPT, HSQC, IR, and ESI-MS spectroscopy. The molecular structures of [Ru(Tp)­(η6-C5H2Ph2-CH(Ph)R)] (R = OMe/OEt) and [Ru(Tp)­(η6-C5H2Ph2-CH(Ph))]PF6 have been determined by X-ray single-crystal diffraction. These complexes have piano-stool structures around the ruthenium center where half of the coordination sites are occupied by the pyrazole ligand while the remaining sites are occupied by either the π-bonded cyclopentadiene (Cp) or fulvene ligand.