IUPAC Nomenclature Mononuclear Rules of Coordination Compounds

IUPAC Nomenclature Mononuclear Rules of Coordination Compounds

The rules are outlined below

1. In naming the entire complex, the name of the cation is given first and the anion second (just as for sodium chloride), no matter whether the cation or the anion is the complex species.
2. In the complex ion, the name of the ligand or ligands precedes that of the central metal atom (This procedure is reversed for writing formulae).
3. Ligand names generally end with ‘O’ if the ligand is negative (‘chloro’ for Cl^–, ‘cyano’ for CN^–, ‘hydrido’ for H^–) and unmodified if the ligand is neutral (‘methylamine’ for MeNH₂).

Special ligand names are ‘aqua’ for water, ‘ammine’ for ammonia, ‘carbonyl’ for CO, nitrosyl’ for NO.

4. A Greek prefix (mono, di, tri, tetra, penta, hexa, etc.) indicates the number of each ligand (mono is usually omitted for a single ligand of a given type). If the name of the ligand itself contains the terms mono, di, tri, like triphenylphosphine, ligand name is enclosed in parentheses and its number is given with the alternate prefixes bis, tris, tetrakis instead.

For example, [Ni(PPh₃)₂Cl₂] is named dichlorobis(triphenylphosphine) nickel(II).

5. A Roman numeral or a zero in parentheses is used to indicate the oxidation state of the central metal atom.
6. If the complex ion is negative, the name of the metal ends in ‘ate’ for example, ferrate, cuprate, nickelate, cobaltate etc.
7. If more than one ligand is present in the species, then the ligands are named in alphabetical order regardless of the number of each. For example, NH₃ (ammine) would be considered as ‘a’ ligand and come before Cl^– (chloro).