Efficient Norbornene (NBE) Incorporation in Ethylene/NBE Copolymerization by Half-Titanocene Catalysts Containing Chlorinated Aryloxo Ligands

Synthesis and structural
analysis of a series of half-titanocenes
containing chlorinated phenoxy ligands of the type Cp′TiCl2(OAr) [Cp′ = Cp, Ar = 2,6-Cl2C6H3 (1), 2,4,6-Cl3C6H2 (2), C6Cl5 (3); Cp′ = indenyl, Ar = 2,6-Cl2C6H3 (4), 2,4,6-Cl3C6H2 (5), C6Cl5 (6)] and CpTiMe2(OAr) [Ar = 2,4,6-Cl3C6H2 (9), C6Cl5 (10)] have been explored. The Ti–O bond
distances in 1–3 are apparently longer
than those of the reported aryloxo-modified half-titanocenes, and
the Ti–O–C­(in phenyl) angles in 1–3 are also rather small. The Cp analogues (1–3) exhibited higher catalytic activities than the reported
(indenyl)­TiCl2(O-2,6-iPr2C6H3) in ethylene copolymerization with
norbornene (NBE) in the presence of MAO; these complexes (1–3) also showed better NBE incorporation than
those reported previously.