| abstract |
A catalyst precursor composition comprising a) a source of chromium, molybdenum or tungsten; b) a first ligand having the general formula (I): n n(R 1 )(R 2 )P—X—P(R 3 )(R 4 ) (I) n nwhere X is a bivalent organic bridging group, R 1 and R 3 are hydrocarbyl groups, and R 2 and R 4 are aromatic groups; and c) a second ligand having the general formula (II): n n(R 1′ )(R 2′ )P—X′—P(R 3′ )(R 4′ ) (II) n nwhere X′ is a bridging group containing nitrogen and R 1′ , R 2″ , R 3′ and R 4′ are hydrocarbyl groups. The present invention also relates to a catalyst system comprising the catalyst precursor composition of the present invention and a cocatalyst. |