PROCESS FOR THE PRODUCTION OF STEREOREGULAR POLYMERS AND ELASTOMERS OF .ALPHA.-OLEFINS AND CERTAIN NOVEL CATALYSTS THEREFOR

The present invention provides a process for the pressure modulated polymerization of one or more .alpha.-olefins having at least 3 carbon atoms, which comprises: contacting the monomer or monomers in a polar or non-polar solvent under polymerization conditions with a homogeneous catalyst system including: a) a cationic form of a racemic mixture of a chiral octahedral transition metal complex or of a non chiral octahedral transition metal complex, comprising 1, 2 or 3 bidentate chelating ligands and no cyclopentadienyl ligands and having C1, C2, or C3 symmetry, provided that when a complex comprising only a single ligand is used for the production of stereoregular polystyrene, said single ligand has natural chirality, and b) an anion of a Lewis acid or a Brönsted acid; and adjusting the pressure so as to obtain at will either a highly stereoregular polymer or copolymer or an elastomer.