Patent ID: 7829749

Claim:
A process for the oligomerization of ethylene comprising contacting ethylene under oligomerization conditions with a catalyst system comprising: a) A transition metal selected from the group consisting of Cr, V, Ti, Ni, and W; b) A ligand defined by the formula: wherein each of Ph 1 , Ph 2 , Ph 3 and Ph 4 is a phenyl group bonded to a phosphorus atom, with the provisos that i) at least one of Ph 1 , Ph 2 , Ph 3 and Ph 4 is ortho substituted with a halogen selected from the group consisting of fluorine, bromine and chlorine; ii) at least one of Ph 1 , Ph 2 , Ph 3 and Ph 4 does not have any substituents in ortho positions; and iii) R 2 is selected from the group consisting of hydrogen, C 1-20 hydrocarbyl and silyl; and c) an activator.