Syntheses of polymethylene bridged dinuclear zirconocenes and investigation of their polymerisation activities

The polymethylene bridged dinuclear zirconocenes [(CH2)(n) (C5H4)(2)][(C9H7)ZrCl2](2) (n = 3 (10), 5 (11), 7 (12), 9 (13)) have been synthesised by treating not only the respective disodium salts of the ligands with two equivalents of (C9H7)ZrCl3 in THF, but also the distannylated derivatives of the ligands with two equivalents of (C9H7)ZrCl3 in toluene. All complexes are characterised by H-1- and C-13-NMR and mass spectrometry and elemental analysis. It turned out that the values of Delta delta = [delta(d) - delta(p)], the chemical shift difference between the distal (delta(d)) and proximal (delta(p)) protons, for the produced dinuclear compounds (0.1 for 10 and 11, and 0.11 for 12 and 13) were smaller than the Delta delta values of the known polysiloxane bridged dinuclear compounds. The chemical shifts of the bridgehead carbons in these complexes are about 135 ppm shifted downfield with respect to the other two resonances at cyclopentadienyl ring (113.7 and 113.7 ppm, respectively). In order to investigate the catalytic properties of the dinuclear complexes and mononuclear metallocenes, ethylene polymerisation has been conducted in the presence of MMAO. The most important feature is that the polymethylene bridged dinuclear metallocenes represent enormously improved activities compared with the activities from the corresponding mononuclear metallocene as well as the polysiloxane bridged dinuclear zirconocenes. In addition, the influence of both the nature and length of the bridging ligand upon the reactivities of the dinuclear metallocenes has also been observed. (C) 1999 Elsevier Science S.A. All rights reserved.