Coordination Compounds

They’re complex.

• A coordination compound is the result of a Lewis acid-base reaction.

M+a + x :L-b [MLx]a-xb

Lewis Acid Lewis Base Complex Ion

A coordination compound is an ionic compound that includes a complex ion.

For example

“Ligand” =“tied on”

Cu+2 + 4:NH3 [Cu(NH3)4] +2

Lewis Acid Lewis Base Complex Ion

The complex ion is a metal ion with ligands “tied on” to it.

For example

Cu+2 +SO4-2 + 4:NH3 [Cu(NH3)4]SO4

• The same complex ion as part of a coordination compound:

tetraamminecopper (II) sulfate

For example

You have seen that the anhydrous copper (II) ion is colorless. In an aqueous system:

[Cu(H2O)6]+2 + 4:NH3 [Cu(NH3)4H2O] +2

…the copper (II) ion is already part of a complex

Remember hydrates?

• CuSO4•5H2O

Remember hydrates?

• CuSO4•5H2O

• Or is it….

[Cu(H2O:)5]SO4?

pentaaquocopper (II) sulfate

We use brackets around a complex ion.

[complex ion]

• A coordination compound has a complex ion (cation, anion or both!)

Naming a coordination compound

• Name the (+) ion first.

• Name (-) ion

• How do we name the complex ion?

• Start with the metal—state the oxidation number.

• Use Latin roots and –ate ending when it is an anion (- ion) .

• Prefixes (with numerical prefixes) show ligands. Many ligands end in –o-.

• Special names when used as a ligand

Special names when used as a ligand

• H2O– aquo-• NH3– ammine-• CN- --cyano-• CO --carbonyl-• OH- --hydroxo-• Chloro- iodo- bromo- etc.

• When using (en) or (EDTA), numerical prefixes include: bis- for 2, tris- for 3, tetrakis- for 4

• Different ligands are listed in alphabetical order (regardless of numerical prefix)