1. Naming Complexes

2. Chloride, Cl- is one element
Naming complexes
Definition: A complex is a central metal ion surrounded by ligands
Examples: [Cu(H2O)6]2+ and [CuCl4]2-
Round brackets, ( ) are used around ligands comprising of more than one element such as:
Water (H2O), ammonia (NH3), hydroxide ions (OH-)
Square brackets, [ ] are used to enclose the complex, with the overall charge written outside
Chloride, Cl- is one element

3. Naming complexes The name of a complex gives you information about:
The number of each type of ligand
The identity of each ligand
The identity of the central metal ion and its oxidation state
Example: [Cr(H2O)4(OH)2]+
4 water (H2O) ligands and 2 hydroxide (OH-) ligands
Chromium(III) ion, Cr3+

4. Number of ligands
When there are two or more ligands around the central metal ion, the number is shown by a prefix
Example: [Cu(H2O)6]2+ Name: Hexa
Number of ligands
Prefix 2 Di 3
Tri 4
Tetra 5
Penta 6
Hexa

5. Name of ligands The identity of each type of ligand is shown by a name
This name is not identical to the name of the ligand
Example: [Cu(H2O)6]2+ Name: Hexaaqua
Ligand
Name in complex
Water
Aqua
Ammonia
Ammine
Chloride
Chloro
Hydroxide
Hydroxo
Cyanide
Cyano

6. Names of metals
The name of the metal changes depending on whether the complex is positively or negatively charged
If the complex is positively charged, the metal is identified by its normal name, with the oxidation state shown in brackets
Example: [Cu(H2O)6]2+ Name: Hexaaquacopper(II)
Example: [Cu(H2O)6]+ Name: Hexaaquacopper(I)
Example: [Co(H2O)6]2+ Name: Hexaaquacobalt(II)

7. Name in negatively charged complex
Names of metals
If the complex is negatively charged, the oxidation state of the metal is still shown in brackets
But the ending of the metal’s name has the suffix ate added to it
Metal
Name in negatively charged complex
Chromium
Chromate
Cobalt
Cobaltate
Copper
Cuprate
Iron
Ferrate
Manganese
Manganate

8. Name in negatively charged complex
Names of metals
Metal
Name in negatively charged complex
Chromium
Chromate
Cobalt
Cobaltate
Copper
Cuprate
Iron
Ferrate
Manganese
Manganate
Nickel
Nickelate
Silver
Argentate
Vanadium
Vanadate

9. Naming complexes
It is acceptable to have two letter a’s next to each other, such as hexaaqua or hexaamine
Formula
Name
[Ag(NH3)2]+
Diamminesilver(I)
[Co(H2O)6]2+
Hexaaquacobalt(II)
[Co(NH3)6]2+
Hexaamminecobalt(II)
[CoCl4]2-
Tetrachlorocobaltate(II)
[AgCl2]-
Dichloroargenate(I)
[Fe(H2O)6]2+
Hexaaquairon(II)
[Ag(CN)2]-
Dicyanoargenate(I)

10. Naming complexes
If two or more ligands are present in a complex, they are named in alphabetical order
It is the name of the ligand which is written in alphabetical order, not the numbering prefix
Examples:
[Cu(H2O)5(OH)]+ Pentaaquahydroxocopper(II)
[Cu(H2O)2(NH3)4]2+ Tetraamminediaquacopper(II)
[Fe(H2O)4(OH)2]+ Tetraaquadihydroxoiron(III)

11. Writing formulae When you write the formula of a complex:
First write the symbol of the central metal ion
Then write the symbols of the ligands in alphabetical order
Include brackets and work out the charge on the outside
Example: Tetraaquadichlorochromium(III) ion
[CrCl2(H2O)4]+ Not [Cr(H2O)4Cl2]+

12. Writing formulae First write the symbol of the central metal ion
Then write the symbols of the ligands in alphabetical order
Include brackets and work out the charge on the outside
Name
Formula
Diaquasilver(I)
[Ag(H2O)2]+
Hexaaquavanadium(III)
[V(H2O)6]3+
Tetracyanonickelate(II)
[Ni(CN)4]2-
Tetrachloroferrate(II)
[FeCl4]2-
Diaquatetrahydroxochromate(III)
[Cr(H2O)2(OH)4]-
Triaaquatrihydroxocuprate(II)
[Cu(H2O)3(OH)3]-