Class 12 Chapter 2 Nomenclature of Coordination Compounds with Examples
Introduction
Naming coordination compounds follows IUPAC rules to unambiguously describe the central metal, ligands, their numbers, and oxidation state. Proper nomenclature is essential for clear communication in inorganic chemistry.
Definition & General Rules
- List ligands first (in alphabetical order ignoring any multiplicative prefixes), then the central metal with its oxidation state in Roman numerals in parentheses.
- Anionic ligands end with “o” (e.g., chloride → chloro, cyanide → cyano).
- Neutral ligands generally retain their name (e.g., ammine for NH₃, aqua for H₂O).
Order of Nomenclature
The sequence is:
- Name and multiplicity of ligands (alphabetically).
- Name of central metal.
- Oxidation state of metal in parentheses.
- Anionic complex ends in “-ate” if overall complex is negative (e.g., ferrate).
Mono‑, Bi‑, Tri‑ etc. for Ligands
| Prefix | Number of Ligands |
|---|---|
| di‑ | 2 |
| tri‑ | 3 |
| tetra‑ | 4 |
| penta‑ | 5 |
| hexa‑ | 6 |
Use “bis‑”, “tris‑”, etc. if ligand names contain numerals or complex names.
Worked Examples
- [Cr(NH3)3Cl2]Cl: triammine dichloro chromium(III) chloride.
- [Co(H2O)4(en)]SO4: tetraaqua ethylenediamine cobalt(II) sulfate.
- [PtCl2(NH3)2]: dichloro diamminoplatinum(II).
Polynuclear Complexes
When multiple metal centers are present, use prefixes μ‑ for bridging ligands and indicate metals alphabetically:
- [Cu2(μ‑OH)2(NH3)4]2+: tetraammine di(μ‑hydroxo) dicopper(II).
Special Ligand Naming
- H2O → aqua
- NH3 → ammine
- CO → carbonyl
- NO → nitrosyl
- C2O42– → oxalato
- EDTA → ethylenediaminetetraacetato
Conclusion
Applying these nomenclature rules ensures systematic, consistent naming of coordination compounds, facilitating clear discussion of their structures and properties.
