Patent ID: 7078363

Claim:
A catalyst for polymerizing olefins, corresponding to the following formula: in which: E is an oxygen or sulfur atom; X is a phosphorus, arsenic or antimony atom; M is a nickel, palladium or platinum atom comprising an unattributed valency; a is 1 or 2; R 1 , R 2 and R 3 , which may be identical or different, may be chosen from hydrogen, alkyl, cycloalkyl, aryl, alkylaryl and arylalkyl radicals, each generally containing from 1 to 20 carbon atoms, the hydroxyl radical, alkoxide radicals with from 1 to 20 carbon atoms, C(O)OR′ in which R′ represents a hydrocarbon-based radical that may contain from 1 to 15 carbon atoms, —SO 3 Y in which Y is chosen from Li, Na, K, NH 4 , NR 4 in which R represents a hydrocarbon-based radical that may contain from 1 to 15 carbon atoms; Rf represents a pentafluorophenyl, trifluoromethyl or heptafluoropropyl group; and R 4 is a group —C(O)OR′wherein R′ is an ethyl, tert-butyl or benzyl group, further wherein: when R′ is an ethyl, tert-butyl or benzyl group, Rf is a pentafluorophenyl group; and when R′ is an ethyl group, Rf is a trifluoromethyl group or a heptafluoropropyl group.