R3.4.8 – Complex ions (HL)
📌 Chemistry of transition elements
- Transition metal ions act as Lewis acids with ligands acting as Lewis bases
- When coordinate bonding between transition metals and ligands occurs, complex ions are formed
- Ligands can be neutral, but they must always contain a lone pair of electrons (since Lewis bases are nucleophiles)
- Transition metals usually bond to several ligands and the number of coordinate bonds a metal ion can form is known as the ‘coordination number’
📌 Charge on ions
- The charge on a complex ion depends on three factors : the charge on the central metal, the charge on the ligands and the coordination number
- The charge on the complex ion can be found by adding the charge of the central metal ion to the charge of each ligand present
Example
Cr3+ with 4 NH3 ligands and 2 F− ligands.
Charge calculation: 3+ + (4 × 0) + (2 × 1−) = 1+
Complex formed: [Cr(NH3)4F2]+