Formation and structures of cationic zirconium complexes in ternary systems rac-(SBI)ZrX2/AlBu3i/[CPh3][B(C6F5)4] (X = Cl, Me)

Using 13C, 1H and 19F NMR spectroscopy, formation of cationic species was studied in ternary systems (SBI)ZrX2/AlBu3i/[CPh3][B(C6F5)4], where X = Cl, Me [(SBI) = rac-Me2Si(Ind)2]. In the first system (X = Cl), the ion pair [(SBI)Zr(μ-Cl)2Zr(SBI)][B(C6F5)4]2 (IV) predominates at low Al/Zr ratios (Al/Zr < 10), whereas at higher Al/Zr ratios (⩾20) in the absence of monomer mainly [(SBI)Zr(μ-H)(μ-C4H7)AlBu2i] [B(C6F5)4] (V) is formed. The binuclear complex [(SBI)Zr(μ-Cl)2Zr(SBI)][B(C6F5)4]2 has been characterized crystallographically. Species V is also formed in the system X = Me at high Al/Zr ratios. In the presence of AlBu3i, IV displays activity in propylene polymerization and is the most likely precursor of the polymerizing species. Consistent mechanisms have been proposed for the reactions in these catalytic systems.

Graphical abstractUsing multinuclear NMR spectroscopy, formation of cationic species was studied in ternary systems (SBI)ZrX2/AlBu3i/[CPh3][B(C6F5)4], where X = Cl, Me. In the first system (X = Cl), the crystallographically characterized ion pair [(SBI)Zr(μ-Cl)2Zr(SBI)][B(C6F5)4]2 predominates at low Al/Zr ratios (Al/Zr < 10), whereas at higher Al/Zr ratios (⩾20) mainly [(SBI)Zr(μ-H)(μ-C4H7)AlBu2i][B(C6F5)4] is formed.Figure optionsDownload full-size imageDownload as PowerPoint slide