3.4.8—Complex ions

Identify the central transition-metal cation and the surrounding ligands. Each ligand donates an electron pair to the metal centre.

Read [Cu(NH₃)₄]²⁺ as one Cu centre with four NH₃ ligands and coordination number 4. Use ligand charges and the overall bracket charge to deduce the metal oxidation state; do not confuse coordination number with oxidation state.

Representative question

[Maximum number: 1]

Which statements are correct for the complex ion $\left[\mathrm{FeCl}_{4}\right]^{2-}$ ?

I. Chloride ions are behaving as ligands.
II. The oxidation state of iron is +3 .
III. Iron ion forms coordination bonds with chloride ions.

I and II only

I and III only

II and III only

I, II and III

Retrieve the route: classify nucleophiles and electrophiles, show heterolysis, write substitution and addition mechanisms, map Lewis coordination, compare SN1/SN2, and restore aromaticity in benzene substitution.

Check electron-pair arrow origin and destination, leaving-group departure, intermediate identity, carbocation stability and the assessed mechanism boundary.

3.4.8—Complex ions

Ligands and Complex Ions

Identifying Complex-Ion Components

Assessment in practice

Electron-Pair Sharing Summary

Question 1