Catalyst systems

A method for tetramerizing ethylene to form 1-octene, the method comprising contacting ethylene with a catalyst system to form a product comprising 1-octene, the catalyst system comprising:

• a catalyst having the structure:
• [(L∩L)CrX2(L1)n]+[BY4]− or [(L∩L)CrX2(L1)n]+[SO2Y]−
• wherein:
• X is a halogen, a (C2-C30) carboxylate, acetylacetonate, or a (C1-C30) hydrocarbyl;
• L1 is a neutral coordinating ligand;
• n is an integer from 0 to 6;
• Y is a (C6-C20)fluorine-substituted aryl, a (C6-C20)fluorine-substituted aryloxy, or a (C1-C20)fluorine-substituted alkoxy;
• and
• L∩L is a bidentate chelating ligand having the structure:
• (R1)(R2)P—Z—P(R1)(R2)
• wherein:
• each R1 and R2 is independently chosen from a (C1-C50) alkyl group or a (C6-C50) aryl group;
• and
• Z is a (C2-C50) alkylene group, a (C6-C50) arylene group, —N(R8)—, —P(R8)—, —B(R8)—, or —Si(R8)2— that links the two P atoms, where R8 is a (C1-C50) alkyl group or a (C6-C50) aryl group;
• and
• at least one aluminum containing agent comprising a reaction product of an organoaluminum compound and an antifouling compound, wherein the antifouling compound comprises one or more organic acids, organic acid salts, esters, anhydrides, or combinations of these.