Nomenclature of Complexes

Nomenclature of Complexes

The rules for naming chemical compounds are established by nomenclature committees of the International Union of Pure and Applied Chemistry (IUPAC).


  • The name of the positive ion is written before the name of the negative ion.

  • The name of the ligand is written before the name of the metal to which it is coordinated.

  • The Greek prefixes mono-, di-, tri-, tetra-, penta-, hexa-, and so on are used to indicate the number of ligands when these ligands are relatively simple. The Greek prefixes bis-, tris-, and tetrakis- are used with more complicated ligands.

  • The names of negative ligands always end in o, as in fluoro (F-), chloro (Cl-), bromo (Br-), iodo (I-), oxo (O2-), hydroxo (OH-), and cyano (CN-).

  • A handful of neutral ligands are given common names, such as aquo (H2O), ammine (NH3), and carbonyl (CO).

  • Ligands are listed in the following order: negative ions, neutral molecules, and positive ions. Ligands with the same charge are listed in alphabetical order.

  • The oxidation number of the metal atom is indicated by a Roman numeral in parentheses after the name of the metal atom.

  • The names of complexes with a net negative charge end in -ate. Co(SCN)42-, for example, is the tetrathiocyanatocobaltate(II) ion. When the symbol for the metal is derived from its Latin name, -ate is added to the Latin name of the metal. Thus, negatively charged iron complexes are ferrates and negatively charged copper complexes are cuprates.
Practice Problem 3:

Name the following coordination complexes.

(a) K4Fe(CN)6

(b) Fe(acac)3

(c) [Cr(en)3]Cl3

(d) [Cr(NH3)5(H2O)][(NO3)3]

(e) [Cr(NH3)4Cl2]Cl

Click here to check your answer to Practice Problem 3

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