STRUCTURE AND REACTIVITY OF BIS(PI-PENTAMETHYLCYCLOPENTADIENYL)(2-METHYLIDENE)TITANACYCLOBUTANE

The reaction of vinyllithium with bis(pi-pentamethylcyclopentadienyl)titanium dichloride in a molar ratio of 2:1 quantitatively yields the unexpected titanacyclobutane derivative Cp2* activated TiC(= CH2)CH2CH2 (2) (Cp* = [C5(CH3)5]). The isolated complex 2 has been characterized by spectroscopic methods and by elemental analysis, and its structure has been confirmed by an X-ray structure determination. The chemical reactivity of 2 is characterized by the splitting of the four-membered ring at higher temperatures, forming a titanocene vinylidene fragment {Cp2*Ti = C = CH2} and ethylene. This cycloreversion is confirmed by the fragmentation behavior in the mass spectrometer, and some aspects of it have been studied by Extended Huckel Model calculations.