Coordination Sphere - First Coordination Sphere

First Coordination Sphere

The first coordination sphere refers to the molecules that are attached directly to the metal. These molecules are typically solvent. The interactions between the first and second coordination spheres usually involve hydrogen-bonding. For charged complexes, ion-pairing is important.

In hexamminecobalt(III) chloride (Cl₃), the cobalt cation plus the six ammonia ligands comprise the first coordination sphere. The coordination sphere of this ion thus consists of a central MN₆ core "decorated" by 24 N-H bonds that radiate outwards.