Methods of oligomerizing olefins

A method of producing oligomers of olefins, comprising reacting an olefin with a catalyst under oligomerization conditions, wherein said oligomerization reaction has a selectivity of at least 70 mole percent for oligomer, and wherein said catalyst is formed from the combination of:

• (1) a ligand characterized by the following general formula:
• wherein R1 and R20 are each independently selected from the group consisting of hydrogen and optionally substituted hydrocarbyl, heteroatom containing hydrocarbyl and silyl, provided that R1 or R20 do not equal T-J, where T-J is as given by the general formula above and defined below;
• T is a bridging group of the general formula -(T′R2R3)—, where T′ is selected from the group consisting of carbon and silicon, R2 and R3 are independently selected from the group consisting of hydrogen, halogen, and optionally substituted alkyl, heteroalkyl, aryl, heteroaryl, alkoxy, aryloxy, silyl, boryl, phosphino, amino, alkylthio, arylthio, and combinations thereof, provided that two or more R2 and/or R3 groups may be joined together to form one or more optionally substituted ring systems having from 3-50 non-hydrogen atoms;
• J is an optionally substituted five-membered heterocycle, containing at least one nitrogen atom as part of the ring;
• (2) a metal precursor compound characterized by the general formula Cr(L)n where each L is independently selected from the group consisting of halide, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, heteroalkyl, substituted heteroalkyl heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkoxy, aryloxy, hydroxy, boryl, silyl, amino, amine, hydrido, allyl, diene, seleno, phosphino, phosphine, ether, thioether, carboxylates, thio, 1,3-dionates, oxalates, carbonates, nitrates, sulfates, ethers, thioethers and combinations thereof, wherein two or more L groups may be combined in a ring structure having from 3 to 50 non-hydrogen atoms;
• n is 1, 2, 3, 4, 5, or 6;
• and
• (3) optionally, one or more activators.