1H and 13C NMR Spectroscopic Study of Titanium(IV) Species Formed by Activation of Cp2TiCl2 and [(Me4C5)SiMe2NtBu]TiCl2 with Methylaluminoxane (MAO)

Using 13C and 1H NMR spectroscopy, the products of the reaction of Cp2TiCl2 with methylaluminoxane (MAO) at Al:Ti ratios of 5:1 to 300:1 have been identified as Cp2TiMeCl, Cp2TiMe2, [Cp2TiMe(μ-Cl)Cp2TiCl]+[Me-MAO]- (II1), [Cp2TiMe(μ-Cl)Cp2TiMe]+[Me-MAO]- (II2), [Cp2TiMe(μ-Me)Cp2TiMe]+[Me-MAO]- (II3), the heterobinuclear ion pair [Cp2Ti(μ-Me)2AlMe2]+[Me-MAO]- (III), and a “zwitterion-like” intermediate, formulated as Cp2TiMe+←Me-Al-⋮MAO (IV). In contrast, [(Me4C5)SiMe2NtBu]TiCl2/MAO gives only zwitterion-like, not heterobinuclear, species.