Donor-ligand-substituted cyclopentadienylchromium(III) complexes:: A new class of alkene polymerization catalyst.: 1.: Amino-substituted systems

Me2NC2H4C5Me4Li reacts with Cr(THF)(3)Cl-3 to give (eta(1):eta(5)-Me2NC2H4C5Me4) CrCl2, in which the complexation of the N-donor atom to the metal atom has been confirmed by X-ray crystallography. A series of related compounds, e.g. (eta(1):eta(5)-cyclo-C4H8NSiMe2OSiMe2C5H4)-CrCl2 has been prepared by varying the substituents on the organic ligand. Further reaction with organomagnesium reagents leads to formation of the corresponding dialkyl-Cr complexes. Related species have been prepared containing imine-, alkoxy-, and alkylthiosubstituted cyclopentadienyl groups as well as the C-donor ligand tetramethylimidazol-2-ylidene. Treatment of these compounds with methylalumoxane (MAO) leads to the formation of highly active catalysts for the oligomerization, polymerization, and copolymerization of ethylene.