HYDROOLIGOMERIZATION OF CYCLOOLEFINS - A VIEW OF THE MICROSTRUCTURE OF POLYNORBORNENE

Hydrooligomerizations of norbornene were carried out using C-2, C-s and C-2 upsilon symmetric zirconocenes with methylaluminoxane as catalysts. The structures of the hydrodimers and -trimers were investigated and correlated to the symmetry of the metallocene. The polymerization of norbornene is shown to proceed by cis-exo insertion. The mechanisms of polymerization and stereocontrol are closely related to the ones observed in the polymerization of alpha-olefins. Thus the C-2 symmetric metallocene features erythrodiisotactic structures, while erythrodisyndiotactic products are observed in case of the C-s symmetric one. This is caused by enantiomorphic site control, while stereospecificity in the hydrooligomerization using Cp(2)ZrCl(2)/MAO is determined by chain end control mechanism.