Ligands and catalyst systems thereof for the catalytic oligomerization of olefinic monomers

A process for the preparation of a ligand having the general formula (I):

• P(R4)—P(R1)(R2)═N(R3) (I)
• wherein:
• the R1 group is selected from a hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl group;
• the R2 group is selected from hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl groups;
• the R3 is selected from hydrogen, a hydrocarbyl group, a substituted hydrocarbyl group, a heterohydrocarbyl group, a substituted heterohydrocarbyl group, a silyl group or derivative thereof;
• the R4 group is an optionally substituted alkylenedioxy, alkylenedimercapto or alkylenediamino structure which is bound to the phosphorus atom through the two oxygen, sulphur or nitrogen atoms of the alkylenedioxy, alkylenedimercapto or alkylenediamino structure or an optionally substituted arylenedioxy, arylenedimercapto or arylenediamino structure which is bound to the phosphorus atom through the two oxygen, sulphur or nitrogen atoms of the arylenedioxy, arylenedimercapto or arylenediamino structure;
• said process comprising reacting:
• i) a compound having the general formula (III);
• (R1)(R2)P—N(R3)—R5 (III)
• and ii) a compound of the formula X—P(R4) wherein X is a halide, and if the R5 group is hydrogen, a HX-acceptor, preferably at a temperature in the range of from −30 to 200° C.