Recent advances in homogeneous chromium catalyst design for ethylene tri-, tetra-, oligo- and polymerization

•Highly active and tunable chromium catalysts for ethylene oligo-/polymerization.•Systematic ligand modification through variations in donor atom and chelation properties.•From oligomeric distributions to selective trimer or tetramer formation.•Highly linear polyethylene with a range of molecular weights.•Correlation between catalytic mechanism and hydrocarbon product.