Comparison of the catalytic activity of Ziegler-type catalysts based on Cp2ZrCl2 and (Cp2ZrCl)2O

The rates of ethylene polymerization catalyzed by Cp₂ZrCl₂-polymethylalumoxane and (Cp₂ZrCl)₂O-polymethylalumoxane are equal. According to NMR and ESR spectral data, the same precatalyst, presumably Cp₂ZrMe₂, is formed in both systems by the action of AlMe₃. This accounts for the equal catalytic activity of the systems based on Cp₂ZrCl₂ and (Cp₂ZrCl)₂O. A scheme of reactions resulting in cleavage of the Zr-O-Zr bridge is proposed and confirmed by spectroscopic data.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2104–2107, December, 1993.