Question

Write the formulae of the following coordination compounds on the basis of I.U.P.A.C. rules: 
(i) Dichloridobis(ethane-1,2-diamine)cobalt(III) chloride 
(ii) Iron(III) hexacyanidoferrate(II) 
 

Hint:

Always write ligands inside square brackets, metals with oxidation states in Roman numerals, and counter ions outside the coordination sphere.

Answer 1

(i) Dichloridobis(ethane-1,2-diamine)cobalt(III) chloride:
- Ligands: Two chloride ions (Cl$^-$) and two ethane-1,2-diamine (en, neutral).
- Central metal: Cobalt in +3 oxidation state.
- Outside the coordination sphere: Chloride counter ions.
Formula: \[ [CoCl_2(en)_2]Cl \] (ii) Iron(III) hexacyanidoferrate(II):
- The compound contains two types of metal centers.
- Iron(II) is coordinated with six cyanide ligands to form \([Fe(CN)_6]^{4-}\).
- Iron(III) balances the charge.
Formula: \[ Fe_4[Fe(CN)_6]_3 \] Conclusion:
According to IUPAC rules, the systematic formulas are: 1. \([CoCl_2(en)_2]Cl\) 2. \(Fe_4[Fe(CN)_6]_3\)