Heptane‐soluble homogeneous zirconocene catalyst: Synthesis of a single diastereomer, polymerization catalysis, and effect of silica supports

Bis(1‐indenyl)‐di[1′S, 2′R, 5′S)‐methoxy]silane (1) was converted into a mixture of corresponding ansa‐diastereomeric zirconocenes. Further purification afforded a single dia‐stereomer, di[(1′S, 2′R, 5′S)‐methoxy] silylene‐bis[η5‐1(R, R)‐(+)‐indenyl] dichlorozirconium (2), which is optically active and hydrocarbon soluble. Extremely rapid ethylene, propylene, and ethylene‐hexene polymerizations were observed both in toluene and n‐heptane solutions; for instance, at 50°C, activity for ethylene polymerization reaches ∼ 1.5×1010 (g of PE/((mol of Zr) · [C2H4] · h). The “bare” zirconocenium ion generated from 2/TIBA/Ph3CB(C6F5)4 exhibits unusual polymerization behaviors; the polymerization activity increases monotonically with temperature of polymerization (Tp) up to a conventional polymerization condition (50–70°C), and the 13C NMR study shows that the isotactic poly‐propylene obtained has fairly high [mmmm] methyl pentad distributions at high Tp (⩽25°C with [mmmm] ∼ 0.93–0.75) and a perfect stereoregularity at low Tp (⩽0°C with [mmmm] > 0.99). The catalyst precursors 2 and Et(Ind)2ZrCl2 (3) supported on silica by different approaches produced poly(olefins) of different molecular weights and stereoregularities, and a methylaluminokane and Ph3CB(C6F5)4 free silica‐supported zirconocene system was found to be activated by triisobutylaluminum.