Synthesis, characterization and reactivity of amido titanium and zirconium complexes

Abstract

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. Amino complexes were prepared either by metathesis reaction of Cp 2ZrCl 2 and the dilithium salt of the bisamido ligand (Me 3SiN(CH 2) 2NSiMe 3) 2−, by transamination reaction of Zr(NMe 2) 4 with two equivalents of the diamine ligand (Me 3SiNH(CH 2) 2NHSiMe 3), and by metathesis reaction of ZrCl 4 · 2THF or TiCl 4 with equimolar amounts of the dilithium salt (Me 3SiN(CH 2) 2NSiMe 3) 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.