CATALYTIC TRIMERIZATION AND TETRAMERIZATION OF OLEFINIC MONOMERS

A catalyst precursor composition comprising: a) a source of chromium, molybdenum or tungsten; b) a first ligand having the general formula (I) ; (R1) (R2) P-X-P(R3) (R4) (I), wherein: X is a bivalent organic bridging group; R1 and R3 are independently selected from, hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl groups, with the proviso that when R1 and R3 are aromatic groups they do not contain a polar substituent at any of the ortho-positions; R2 and R4 are independently selected from optionally substituted aromatic groups, each R2 and R4 bearing a polar substituent on at least one of the ortho-positions; and c) a second ligand having the general formula (II) ; (R1') (R2')P-X'-P(R3') (R4') (II), wherein: X' is a bridging group of the formula -N(R5')-, wherein R5' is selected from hydrogen, a hydrocarbyl group, a substituted hydrocarbyl group, a heterohydrocarbyl group, a substituted heterohydrocarbyl group, a silyl group or derivative thereof; and R1', R2', R3' and R4' are independently selected from hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl groups of which at least one of R1', R2', R3' and R4' is substituted with a polar substituent, or R1', R2', R3' and R4' are independently selected from hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl and substituted heterohydrocarbyl groups, wherein any substituents on one or more of R1', R2', R3' and R4' are non-polar. The present invention also relates to a catalyst system comprising the catalyst precursor composition of the present invention and additional component; d) a cocatalyst. The present invention further relates to a process for the trimerization and tetramerization of olefinic monomers, particularly the trimerization and tetramerization of ethylene to 1-hexene and 1-octene, wherein the process comprises contacting at least one olefinic monomer with the catalyst system of the present invention.