Chromium phosphinyl hydroisoindole amidine complexes for tetramerization of ethylene

A process comprising:

• a) contacting in a reaction zone
• i) ethylene at a partial pressure in a range of from 5 psi to 2500 psi;
• ii) a catalyst system comprising;
• (a)(1) a bicyclic 2-[(phosphinyl)aminyl] cyclic imine chromium salt complex having Structure BPACICr I or Structure BPACICr II
• or
• (a)(2) a chromium salt and a bicyclic 2-[(phosphinyl)aminyl] cyclic imine having Structure BPACI I or Structure BPACI II
• wherein
• R21, R22, R23, and R24 independently are a hydrogen or a C1 to C30 organyl group,
• L1, L2, and L3 independently are a C1 to C30 a hydrocarbylene group,
• R4 and R5 independently are a C1 to C30 organyl group and
• R4 and R5 optionally are combined to form L45 forming a ring or ring system including the phosphorus atom where L45 is a C1 to C30 organylene group,
• CrXp is a chromium salt wherein X is a monoanion, and wherein p is an integer from 2 to 6, and
• (b) an organoaluminum compound;
• iii) optionally an organic reaction medium;
• iv) optionally hydrogen;
• and
• b) forming an oligomer product in the reaction zone.