Coordination Number 6

• Hexagonal planar Geometry: Unknown for first row transition metal ions, although the arrangement of six groups in a plane is found in some higher coordination number geometries.

• Trigonal prism Geometry: Most trigonal prismatic compounds have three bidentate ligands such as dithiolates or oxalates and few are known for first row transition metal ions.

• Octahedral (Oh): The most common geometry found for first row transition metal ions, including all aqua ions. In some cases distortions are observed and these can sometimes be explained in terms of the Jahn-Teller Theorem.

Figure 1: [Co(en)₃]Cl₃(left) and [CoCO₃(NH₃)₅]⁺ (right)