Reactivity of fully methylated η3:η4-allyldiene-(η5-cyclopentadienyl)titanium(II) towards alkynylketones. The crystal structure of an unexpected 1:2 adduct

Fully methylated η3:η4-allyldiene(η5-cyclopentadienyl)titanium(II) (1) reacts with alkynylketones RCCC(O)Me (R=SiMe3 (3a) and ferrocenyl (3b)) to give the expected products of the CO group insertion into one Ti–CH2 bond 4a and 4b, respectively. Compound 4a could not be isolated in pure form due to its high solubility; a minor product of two-fold addition (5) was isolated instead. Complex 5, formally [1+2 3a], was characterized as a monocyclopentadienyl bis(alkoxy)organyl complex, where the alkoxyorganyl ligand arises from CO insertion into one Ti–CH2 and the Ti–C(cyclopentadienyl) bonds. The structures of compounds 4b and 5 were determined by single-crystal X-ray diffraction.