Process for oligomerization of olefins that uses a catalytic composition that comprises an organometallic complex that contains an alkoxy ligand that is functionalized by a heteroatom

A process for oligomerization of olefins into compounds or into a mixture of compounds of the formula CpH2p with 4≦p≦80, said process comprising:

• oligomerizing an olefin feedstock in the presence of a catalytic composition comprising at least one organometallic complex of an element of group IV selected from titanium, zirconium, and hafnium, wherein said organometallic complex contains at least one alkoxy ligand functionalized by a heteroatom that is selected from nitrogen, oxygen, phosphorus, and sulfur or by an aromatic group, and said organometallic complex is of the following formula:
• [M(OR)mY(4-m)]
• in which:
• M is an element from group IV selected from titanium, zirconium, and hafnium,
• Y is an atom of chlorine or bromine, a hydrocarbyl radical having 1 to 30 carbon atoms, or a radical selected from alkoxy R′O—, amido R′2N—, and carboxylate R′COO—, where R′is a hydrocarbyl radical having 1 to 30 carbon atoms,
• m is an integer of 1 to 4, and
• the ligand —OR is an organic compound selected from alkoxy ligands of the formula:
• O—(CR10R11)n—X-L
• in which:
• (CR10R11)n is —CH2—, —(CH2)2—, —(CH2)3—, —(CH2)4—, —(CH2)5—, —C(CH3)2—, —C(CH3)2—CH2—, —C(CH3)2—CH2—CH2—, —C(CF3)2—, —C(CF3)2—CH2— or —C(CF3)2—CH2—CH2—,
• R10and R11each represent a hydrogen atom, —CH3, or —CF3
• L is —PR4R5,
• X is a hydrocarbon group CR7R8, an oxygen atom, or a group that comprises —NR9,
• R4 and R5 are each an alkyl or aryl group that is substituted or unsubstituted,
• R7, R8, and R9 each represent a hydrogen atom or a hydrocarbon chain, that may or may not be cyclic, having 1 to 30 carbon atoms, and
• n is an integer in the range of 1 to 5.