Transition Metals form Complex Ions

Complex ions

Complex ion = a central metal ion surrounded by several groups/atoms that are linked by coordinate bonds. These groups are called ligands. 

A ligand is a small molecule that has a lone pair which it uses to coordinate bond with a transition metal. 

e.g. water, ammonia, halide ions.

HOW? Transition metals have vacant orbitals for bonding. Ligands are small molecules that have a positive charge, and so they seek out electron-rich nucleophiles. 

When transition metal ions are placed in a solution they form coloured complexes with water molecules. These are either octahedral (90 degrees) or tetrahedral (109.5 degrees)

6-co-ordinated complex ions

• Octahedral shape.
• Transition metal attached to six ligands.

1. [Cu(H₂O)₆]²⁺ = Blue complex.

2.  [Fe(H₂O)₆]²⁺ = Pale green complex.

3.  [Fe(H₂O)₆]3⁺ = Yellow complex.

4.  [Cr(H₂O)₆]3⁺ = Dark green complex.

5.  [Co(H₂O)₆]2+ = Pink complex. 

4-co-ordinated complex ions 

• Tetrahedral shape.
• Transition…