Shapes of Complex Ions

Transition metal ions commonly form octahedral complexes with small ligands (eg H2O and NH3).

Octahedral complexes can display cis–trans isomerism (a special case of E–Z isomerism) with monodentate ligands and optical isomerism with bidentate ligands.

Transition metal ions commonly form tetrahedral complexes with larger ligands (eg Cl–).

Square planar complexes are also formed and can display cis–trans isomerism.

Cisplatin is the cis isomer.

Ag+ forms the linear complex [Ag(NH3)2]+ as used in Tollens’ reagent.