Nickel-based catalytic composition in the presence of a specific activator and use thereof in a olefin oligomersation method

A composition comprising:

• at least one precursor of nickel with an oxidation number of(+II),
• at least one activating agent with formula [R3−mAlXm]n, the group X being an alkoxy group —OR or a halogen, the groups R being mutually identical or different and selected from alkyl or aromatic groups, n having a value of 1 to 2, m having a value of 1 to 3,
• and at least one mixture of a phosphine halide YP(AR1a) (A′R1b) and a sulfonamide compound with formula R2SO2NH2, optionally in the presence of a Lewis base denoted Z, in which
• A and A′, which may be identical or different, are independently O, S, NR3 or a single bond between the phosphorus atom and a carbon atom,
• the group R3 is either a hydrogen atom or an alkyl group, which may or may not be cyclic, which may or may not be substituted and which may or may not contain heteroelements, or an aromatic group, which may or may not be substituted and which may or may not contain heteroelements,
• the groups R1, represented by R1a and R1b, with R1a and R1b being mutually identical or different and which may or may not be bonded together, are selected from alkyl groups which may or may not be cyclic, which may or may not be substituted and which may or may not contain heteroelements, and from aromatic groups, which may or may not be substituted and which may or may not contain heteroelements,
• the group R2 is selected from alkyl groups, which may or may not be cyclic, which may or may not be substituted and which may or may not contain heteroelements, and aromatic groups, which may or may not be substituted and which may or may not contain heteroelements,
• the group Y being a halogen.