Mixed bis-imine pyridine ligands of formula (I), wherein Z₁, which is different from Z₂, is an optionally substituted aryl group; and Z₂ comprises an optionally substituted heterohydrocarbyl moiety, or an optionally substituted aryl group in combination with a metal, said optionally substituted aryl group being -co-ordinated to the metal; ##STR1##

mixed bis-imine pyridine complexes comprising a ligand of formula (I); mixed ionic bis-imine pyridine complexes comprising a ligand of formula (I); and processes for the production of alpha olefins from ethylene, using said complexes.