Catalyst composition for preparation of syndiotactic vinyl aromatic polymers

Claim 1

A catalyst composition for preparing polymers of vinyl aromatic monomers having high stereo-regularity comprising: 1) a metal complex of the formula: [Cp.sub.m MX.sub.n X'.sub.p ].sup.+ A.sup.- wherein: Cp is a single η 5 -cyclopentadienyl group or a η 5 -substituted cyclopentadienyl group; M is a metal of Group 3, 4, 5, 6, 8, 9, 10 or the Lanthanide Series of the Periodic Table; each X independently is an inert anionic ligand or a group of formula R, with the proviso that at least one X is R; X' is an inert, neutral donor ligand; each R independently is R' or hydride, wherein R' is hydrocarbyl, silyl or a mixture thereof, optionally substituted with one or more halogen atoms or alkoxy groups, said R' having up to 20 carbon and/or silicon atoms; m and p are independently 0 or 1; n is an integer greater than or equal to 1; and the sum of m and n is one less than the valence of M; and A- is a noncoordinating, compatible anion of a Bronsted acid salt; and 2) an aluminum, magnesium or zinc metal hydrocarbyl, the molar ratio of the metal complex: metal hydrocarbyl being 1:1 to 1:1000; said metal complex and metal hydrocarbyl being combined prior to contacting of the metal complex with a vinyl aromatic monomer.