Vibrational spectroscopy is one of the most useful tools

2, each ligand carries a 2-charge and each O has three lone pairs. The metal–ligand σ bonds result from the interaction of one lone pair on each O with the metal. One set of lone pairs (one from each O) is often represented as delocalized into the π structure of the ligand as shown in this line drawing (at other times the C–O bonds are simply draws as single bonds).