Process to prepare ethylene propylene elastomer

A process for the preparation of an elastomeric ethylene-propylene polymer wherein said process is characterized by being undertaken under solution polymerization conditions in the presence of a catalyst system which comprises:

• 1) an unbridged catalyst having a single cyclopentadienyl ligand and a monosubstituted monoanionic nitrogen ligand;
• and
• 2) a boron activator;
• wherein said catalyst is defined by the formula:
• wherein Y is selected from the group consisting of:
• ai) a phosphorus substituent defined by the formula:
• wherein each R1 is independently selected from the group consisting of a hydrogen atom, a halogen atom, C1-20 hydrocarbyl radicals which are unsubstituted by or further substituted by a halogen atom, a C1-8 alkoxy radical, a C6-10 aryl or aryloxy radical, an amido radical, a silyl radical of the formula:
• —Si—(R2)3
• wherein each R2 is independently selected from the group consisting of hydrogen, a C1-8 alkyl or alkoxy radical, C6-10 aryl or aryloxy radicals, and a germanyl radical of the formula:
• —Ge—(R2′)3
• wherein R2′ is independently selected from the group consisting of hydrogen, a C1-8 alkyl or alkoxy radical, C6-10 aryl or aryloxy radicals, and a germanyl radical;
• and
• aii) a substituent defined by the formula:
• wherein each of Sub1 and Sub2 is independently selected from the group consisting of hydrocarbyls having from 1 to 20 carbon atoms;
• silyl groups, amido groups and phosphido groups;
• Cp is a ligand selected from the group consisting of cyclopentadienyl, substituted cyclopentadienyl, indenyl, substituted indenyl, fluorenyl and substituted fluorenyl;
• X is an activatable ligand and n is 1 or 2 depending upon the valence of M and the valence of X;
• and
• M is a group 4 metal selected from the group consisting of titanium, hafnium and zirconium.