Tetrabenzo[a,c,g,i]fluorenyltitanium(III) and -(IV) Complexes: Syntheses, Reactions, and Catalytic Application

Reacting tetrabenzo[a,c,g,i]fluorenyllithium {TbfLi(THF)₄ (1)} with TiCl₃(THF)₃ (2) leads to the formation of the η⁵-tetrabenzo[a,c,g,i]fluorenyltitanium(III) derivative TbfTiCl₂(THF) (3), which can be conveyed to the titanium(IV)complex TbfTiCl₃ (4) by oxidative chlorination with CCl₄. Subsequent reaction with various lithium phenoxides gives a series of titanium complexes of the type TbfTiCl₂(OAr) (Ar = 4-^tBuC₆H₄ (5), 2,6-Me₂C₆H₃ (6), 2,4,6-Me₃C₆H₂ (7), 2,6-ⁱPrC₆H₃ (8), 2,6-Ph₂C₆H₃ (9)). Furthermore, 3 was reacted with radicals or radical-generating peroxides to form the complexes TbfTiCl₂TEMPO (10) and TbfTiCl₂O^tBu (11). All compounds were characterized by IR, MS, and NMR measurements and X-ray crystallography. Finally, compounds 6, 8, 9, and 10 were subjected to ethylene polymerization experiments using d-MAO. The activities increase in the following order [kG(PE)mol(Ti)⁻¹ h⁻¹ bar⁻¹]: 6 (320) < 8 (320) < 10 (760) < 9 (1000).