5 Steps to a 5 AP Chemistry

When writing formulas the metal (central atom) is alwayslisted first within the brackets.

However, when writing names the metal name is alwaysgiven last. Any material not listed

within the brackets is named separately.

Examples:

[Ru(NH 3 ) 5 (N 2 )]Cl 2 coordination compound

[Ru(NH 3 ) 5 (N 2 )]^2 + complex ion (cationic)

[PtNH 3 Cl 2 (C 5 H 5 N)] coordination compound

[IF 6 ]− complex ion (anionic) (the name must end in -ate)

K[IF 6 ] coordination compound (same -ate ending)

If everything in the formula is enclosed within one set of brackets, the entire name will

be one word. If there is material outside the brackets, this outside material is named

separately.

Just as with simpler compounds, cations are always named before anions. Thus,

a cationic complex would be the first word in the name, and an anionic complex would be

the last word in a name (with an ateending).

Examples:

[Ni(H 2 O) 4 Cl 2 ] tetraaquadichloronickel(II)

[Co(NH 3 ) 6 ]Cl 3 hexaamminecobalt(III) chloride

K 2 [PtCl 4 ] potassium tetrachloroplatinate(II)

When naming a complex, or when writing the formula for a complex, the ligands

are listed alphabetically. Again, do not forget that metals are first in the formula and last in

the name.

The names of anionic ligands always end in an o. Neutral ligands are basically

unchanged. Two common exceptions in the case of neutral ligands are NH 3 =ammine

(note the double m), and H 2 O =aqua. Other common ligands and their names are listed

in Appendix C.

Multiple identical ligands have prefixes added to designate the number of such ligands:

2 di- 5 penta- 8 octa-

3 tri- 6 hexa- 9 nona-

4 tetra- 7 hepta- 10 deca-

Examples:

[Co(NH 3 ) 6 ]Cl 3 hexamminecobalt(III) chloride

[Cr(NO) 4 ] tetranitrosylchromium(0)

If the ligand name contains a prefix or begins with a vowel (except ammine and aqua),

alternate prefixes should be used:

2 bis- 5 pentakis- 8 octakis-

3 tris- 6 hexakis- 9 nonakis-

4 tetrakis- 7 heptakis- 10 decakis-

When using the alternate prefixes, it is common practice to enclose the name of

the ligand within parentheses. Either type of prefix is added after the ligands have been

alphabetized.

58  STEP 4. Review the Knowledge You Need to Score High