Question

Write the IUPAC names of the following coordination compounds:
(i) \( [Co(en)_2ClBr]NO_3 \)
(ii) \( [Ni(NH_3)_4][Pt(CN)_4] \)

Hint:

Name ligands alphabetically with 'bis' for en; work out the metal oxidation states from the counter-ion charges, and give the anionic complex an '-ate' ending.

Answer 1

Part (i): \( [Co(en)_2ClBr]NO_3 \)
Step 1: Name the ligands in alphabetical order with anionic ligand suffixes '-o': bromido, chlorido, and ethane-1,2-diamine (en). 'en' appears twice, so use the multiplying prefix 'bis' (as 'en' already contains a numerical part) → bis(ethane-1,2-diamine).
Step 2: Find the oxidation state of Co. The nitrate counter ion is \( NO_3^- \), so the complex ion is \( [Co(en)_2ClBr]^+ \). Let Co = x: \( x + 2(0) + (-1)_{Cl} + (-1)_{Br} = +1 \Rightarrow x = +3 \).
Step 3: Assemble: ligands alphabetically (bromido, chlorido, bis(ethane-1,2-diamine)) + metal(oxidation state) + counter ion.
Name: bromidochloridobis(ethane-1,2-diamine)cobalt(III) nitrate.

Part (ii): \( [Ni(NH_3)_4][Pt(CN)_4] \)
Step 1: Both ions are complex. Name the cation first, then the anion. Cation \( [Ni(NH_3)_4]^{2+} \): ammine ligand × 4 = tetraammine. Ni oxidation state: \( x + 4(0) = +2 \Rightarrow x = +2 \) → nickel(II).
Step 2: Anion \( [Pt(CN)_4]^{2-} \): cyanido ligand × 4 = tetracyanido; the anionic complex takes the '-ate' suffix on the metal (platinate). Pt oxidation state: \( x + 4(-1) = -2 \Rightarrow x = +2 \) → platinate(II).
Step 3: Combine cation then anion.
Name: tetraamminenickel(II) tetracyanidoplatinate(II).