Shape and Polydentate Compunds

[005532550]

How does shape influence the number of binding sites a ligand can have? Also, is any compound that has a ligand with lone pairs considered polydentate?

[Chem_Mod]

Shape influences how accessible the lone pairs are to bind to the metal center. For example, double bonds may make the compound unable to rotate, so distant lone pairs cannot both bind to the same metal center. Additionally, lone pairs on opposite or distant sides may not be able to physically, due to steric hinderance, reach the same metal center at the same time. A ligand with MULTIPLE lone pairs and the ability to bind multiple times is considered polydentate.