## Chemistry: Molecular Approach (4th Edition)

In general, complexes with strong field ligands have fewer unpaired electrons compared to the free metal ion and are therefore called low-spin complexes. Complexes with weak field ligands, in contrast, have the same number of unpaired electrons as the free metal ion and are called high-spin complexes. For example, $Fe{{\left( {{\left( CN \right)}_{6}} \right)}^{4-}}$: low-spin complex $Fe{{\left( {{H}_{2}}{{O}_{6}} \right)}^{2+}}$: high-spin complex