Complex IonsNaming 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• 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. 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)

2. 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