Complex Ions
Naming and Formula Writing
Definitions
• Complex ion – A combination of a metal ion and a ligand
• Ligand – Group bonded to a metal ion
• Coordination Compound – A neutral compound containing a
complex ion
• Ligands you must know
•
•
•
•
•
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OH- Hydroxo
CN- Cyano
SCN- Thiocyano
H2O Aqua
NH3 Ammine (yes, with 2 m’s)
F-, Br-, Cl- , I- Fluoro, Bromo, Chloro, Iodo
Naming
1. The name begins with the ligand. Use your prefixes to tell
how many of the ligand are present.
2. Then name the metal ion.
1.
2.
If the overall charge of the complex ion is positive, place the
charge of the metal ion in ( ) even if we have never done it
before….Al (III)
If the overall charge of the complex ion is negative, use the
Latin form of the metal, if applicable, then add –ate and ( ) for
the charge of the metal.
Trying a Few
[Al(OH)4]There are four hydroxo, therefore, begin with Tetrahydroxo
The overall complex ion is negative, so the metal is named
aluminate.
The Al has a charge of 3+, because the OH- and there are four
of them and the overall charge = -
Name: tetrahydroxoaluminate (III) ion
Another One
[Ag(NH3)2]+
Ligand = diammine
Metal = silver (complex ion is +)
Metal charge = +, as the NH3 is neutral
Name: diammine silver (I) ion
One More
[Ag(CN)2]Ligand = dicyano
Metal = argentate (complex ion is -)
Name: dicyano argentate (I) ion
How do you know how many
ligands to add?
• As a general rule, the number of ligands you attach to a metal
ion will equal 2 times the charge of the metal ion.
• Example:
• Al3+
with the ligand OH-
[Al(OH)6]3-
hexahydroxo aluminate (III) ion
• Example:
• Cu2+ with the ligand NH3
[Cu(NH3)4]2+
tetraammine copper (II) ion