(i) σ-bonded complexes Trimethyl aluminium is a σ-bonded organometallic compound in which the metal and carbon atom of ligand are joined together with a σ-bond. It exists at a dimer and two methyl group act as bridges between two aluminium atoms.
(ii) π-complexes Zeise's salt and ferrocene are π-bonded organometallic complexes. In these compounds, the π-electrons of the organic compounds interact with the metal ions and thus occupy one of the coordination site.
K+[PtCl3(η2−C2H4)]‌‌Fe(η2−C5H5)2] Complexes with characteristics of both σ-and π-bonding In metal carbonyl Cr(CO)6, the carbon of CO donates a pair of electrons to the metal. The metal carbon bond in metal carbonyls has σ as well as π electrons.