Definitions of some important terms pertaining to Coordination Compounds Preparation and Properties
Definitions of some important terms Pertaining to Coordination Compounds :
→ Central lon: (Centre of Coordination)
- The cation to which one or more neutral molecules or anions are attached is called as centre of coordination.
- Since the central ion acts as an acceptor and thus has to accommodate electron pairs donated by the donor atom of the ligands, it must have empty orbitals.
- This explains why the transition metals having empty d-orbitals form coordination compounds very readily.
- In the complexes [Ni(NH3)6]2+ and [Fe(CN)6]3- Ni2+ and Fe3+ respectively are the central ions.
→ Ligand :
- The neutral molecules, anions or cations which are directly linked with the central metal atom or ion in a complex ion are called ligands. For example, in [COCI(NH3)5]2+ ligand is NH3, central ion is Co3+.
- Ligand donates a pair of electrons to the central atom.
- Ligands are attached to the central metal ion or atom through coordinate bonds or dative linkage.
- Ligands are normally polar molecules like NH3; H2O: or anions much as Cl–, OH–, CN– etc.
which contain atleast one unshared pair of electrons.
- With few exceptions, free ligands have lone pair of electrons that is not engaged in bonding. For example : C ≡ N:–, :CE:–
- Ligands may be called as Lewis base and central ion as Lewis acid.