Coordination
Compounds
Chapter 22
20.3 Coordination
Compounds
Metallic salts are surrounded by water
when they dissolve.
 Dipoles in water are attracted to the
ions.

Complexes and Ligands
Ions in which a metal ion and either
water or ammonia molecules
compose a unit are examples of
coordination compounds or complex
ions.
 Compounds containing a complex ion
as part of their structure are called
coordination compounds.

Complexes and Ligands

You can write a complex ion as a
hydrate, or (more current) as a single
structure.
NiCl2•6H2O OR [Ni(H2O)6]Cl2
Complexes and Ligands
All coordiation complexes contain a
metal atom/ion as the central part of
the structure.
 Ligands are molecules or ions bonded
to the metal.


the number of ligands attached to the
metal defines the coordination number
Complexes and Ligands

Ligands are usually either neutral
molecules or anions. Must have a
lone pair of electrons (Lewis base)!
The attachment is called a coordinate
covalent bond.
 Net charge is the sum of the charges
on the metal and its attached groups.

Formulas of Coordination
Complexes

Problem: Give the formulas of the following
coordination complex:
A Ni2+ ion is bound to two water
molecules and two bidentate oxalate
ions.
This complex ion is constructed from two
neutral H2O molecules, two C2O42- ions, and
one Ni2+ ion, so the net charge is 2-. The
formula is [Ni(C2O4)2(H2O)2]2-.
Practice Problem
What is the formula of a complex ion
composed of one Co3+ ion, three
ammonia molecules, and three Clions?
 Determine the metal’s oxidation
number and coordination number in
(a) K3[Co(NO2)6]
(b) Mn(NH3)4Cl2

Naming Coordination
Compounds
Name the cation first and then the
anion.
 For a complex ion, name the ligands
first, in alphabetical order (disregard
prefix), followed by the name of the
metal.

Naming Coordination
Compounds
Ligands and their names:
 If anion is –ite or –ate, the final e is
changed to o.
 If anion ends in –ide, the ending is
changed to o.
 If neutral molecule, its common name
is used except for water (aqua),
ammonia (ammine), and CO
(carbonyl).
 Use prefixes as needed.

Naming Coordination
Compounds
If the coordination complex is an
anion, the suffix –ate is added to the
metal name.
 Following the name of the metal, the
oxidation number of the metal is given
as Roman numerals.

Practice Problem
Name the following coordination
compounds.
 [Ni(H2O)6]SO4
 K[Pt(NH3)Cl3]
 K[CuCl2]

Homework
After reading Section 22.3, you should
be able to do the following:
 P.1055 (9-18)
