“…Relatively stable di-Zr complexes [18] could hardly be seen as prototype of catalytic species. Zr-Al complexes can vary in a number of coordinated Al atoms [15,19,20,21,22,23,24,25,26,27]. To explain experimental facts, we recently proposed a binuclear Zr-Al model (Scheme 2) [13,28] involving the catalytic species that are closely related to discrete ionic pairs containing Zr-(μ-Me) 2 AlMe 2 fragments formed at the initial stage of zirconocene dichloride activation by MAO [29,30,31,32,33,34,35].…”