New tethered ansa-bridged zirconium catalysts: Insights into the "self-immobilization" mechanism

New -alkenyl-substituted ansa-bridged bisindenyl zirconium complexes are prepared and tested as self-immobilized catalysts for ethene polymerization. But, even at very high concentration of the tethered complexes and low pressure of ethene, there is no evidence of their insertion into the polyethene chain. A cross polymerization test, performed by copolymerizing the tethered complexes with ethene using rac-Me2Si(2-MeBenzInd)2ZrCl2 (MBI), does not lead to their incorporation into the polyethene chain. However, the corresponding ligand proves to be a suitable comonomer for ethene, and, through copolymerization promoted by MBI, innovative poly(ethene-co-2,2-bis[(1H-inden-3-yl)-hex-5-ene) copolymers are prepared and characterized by 13C NMR.