TETRAMERIZATION LIGANDS

摘要

An ethylene oligomerization catalyst which contains a bridged diphosphine ligand having the formula (R1)m(X1)n P1-bridge-P2(R2)X2 wherein R1 and R2 are independently selected from the group consisting of hydrocarbyl and heterohydrocarbyl; X1 is selected from the group consisting of halogen, hydrocarbyl and heterohydrocarbyl; m is 1 or 2; n is 0 or 1; m + n = 2; bridge is a divalent bridging group bonded to P1 and P2; and X2 is halogen. The present ligands differ from prior diphosphine ligands used in olefin oligomerization processes in that at least one halide substituent is directly bonded to at least one P atom of the ligand. The behavior of catalysts that are prepared from a chromium salt and the present ligands is unusual and surprising. A ligand of this invention with a single F substituent and three phenyl substituents may be used to prepare a selective tetramerization catalyst which produces an oligomerization product having an octene selectivity of about 35 weight %. The replacement of the single F atom with a single Cl atom can increase the octene selectivity to about 70-75 weight %.