Preparation and reactions of monocyclic bis(cyclopentadienyl)titanacyclopentenes and -pentadienes

A combination of Cp2TiCl2–2EtMgBr was found to be very effective for the formation of monocyclic titanacyclopentenes in excellent yields. On the other hand, a combination of Cp2TiCl2–2n-BuLi was used for intermolecular coupling of two alkynes to form titanacyclopentadienes in good to excellent yields. A reaction temperature range from −10 to −30 °C was critical for the success of the combinations. Reactions of these in situ-prepared titanacycles show interesting similarities to or differences from their zirconacycle analogs.