The polymerization of ethylene and propylene was studied by using a series of mono-and spirocyclic coordinatively unsaturated early transition metal amides as pre-catalysts. Amido complexes were prepared either by metathesis reaction of Cp2ZrCl2 and the dilithium salt of the bisamido ligand (Me3SiN-(CH2)2-NSiMe3)2-, by transamination reaction of Zr(NMe2)4 with two equivalents of the diamine ligand (Me3SiNH-(CH2)2-NHSiMe3), and by metathesis reaction of ZrCl4 • 2THF or TiCl4 with equimolar amounts of the dilithium salt (Me3SiN-(CH2)2-NSiMe3)2-. The complexes obtained were characterized by standard spectroscopic techniques. 'Cationic' polymerization catalysts were generated from the early transition-metal amides with methylalumoxane. Polymerization activity is dependent on catalyst and co-catalyst concentrations.
- Group 4