 Zeise 's salt , containing an ethylene ligand , was one of the first organometallic compounds discovered . Dichloro ( cycloocta @-@ 1 @,@ 5 @-@ diene ) platinum ( II ) is a commercially available olefin complex , which contains easily displaceable cod ligands ( " cod " being an abbreviation of 1 @,@ 5 @-@ cyclooctadiene ) . The cod complex and the halides are convenient starting points to platinum chemistry . 
