High activity ethylene polymerisation catalysts based on chelating diamide ligands

Treatment of Zr(NMe2)4 with RNH(SiPh2)NHR and RNH(Me2SiCH2CH2SiMe2)NHR (R = 2,6-Me2C6H3) affords the four- and seven-membered chelate complexes {Zr[RN(SiPh2)NR](NMe2)2(HNMe2)} and {Zr[RN(Me2SiCH2CH2SiMe2)NR](NMe2)2} respectively; a dramatic effect of chelate ring size on ethylene polymerisation activity and kinetic profile is found.