Catalyst and process for the syndiotactic polymerization of vinylaromatic compounds

A catalyst for the polymerization of vinylaromatic monomers, comprising the product obtained by contacting with each other the following two components (A) and (B):

• (A) an η5-cyclopentadienyl complex of titanium;
• (B) an organo-oxygenated compound of aluminum;
• wherein said catalyst contains at least one carboxylate having the following formula:
• R—COO—G (I)
• wherein R—COO is a carboxylic group comprising the organic radical R having from 1 to 30 carbon atoms, and G independently represents hydrogen or a metal atom,
• wherein said η5-cyclopentadienyl titanium complex has the following formula (II):
• wherein:
• Ti is a titanium atom in oxidation state +3 or +4;
• A is an anion containing an η5-cyclopentadienyl ring co-ordinated to the titanium atom;
• each of the R′ substituents and R″ independently represents a substituent group selected from hydride, halide, a C1-C8 alkyl group, a C3-C12 alkylsilyl group, a C5-C8 cycloalkyl group, a C6-C10 aryl group, a C1-C8 alkoxy group, a C1-C30 carboxylic group, and a C2-C10 dialkylamide group;
• or R″ represents a second anion containing an η5-cyclopentadienyl ring co-ordinated to the titanium, and may also be covalently bound to A by means of a divalent bridged group, so as to form a cyclic structure comprising at least 4 atoms, one of which is the titanium atom,
• “n” is equal to 1 or 2 respectively when the titanium is in oxidation state +3 or +4.