Write the structures and names of all the stereoisomers of the following compounds:

(i) [Co(en)₃]Cl₃
(ii) [Pt(NH₃)₂Cl₂]

(iii) [Fe(NH₃)₄Cl₂]Cl

Stereoisomerism is of 2 types:-

•Geometrical isomerism.

•Optical isomerism

(i) [Co(en)₃]Cl₃

There are 3 –en groups attached, so it would be tris (ethan-1,2-diamine). The central atom is cobalt and it has +3 charge on it (Each Cl atom contribute to -1 charge and –en has 0 charge and overall the molecule is electrically neutral). So the name stands as:

tris (ethan-1,2-diamine) cobalt(III) chloride.

(ii) [Pt(NH₃)₂Cl₂]

There are 2 –NH₃ (ammine) atoms and 2 –Cl (chlorido) atoms but alphabetically, ammine comes before chlorido, so the name starts as ‘diamminedichlorido’. The central atom platinum has +2 charge (as Cl atoms carry -1 charge each and NH₃ atoms carry no charge). So the name stands as:

diamminedichloridoplatinum(II)

The geometrical isomers are cis and trans forms.

(iii) [Fe(NH₃)₄Cl₂]Cl

There are 4 –NH₃ (ammine) atoms and 2 –Cl (chlorido) atoms but alphabetically, ammine comes before chlorido, so the name starts as ‘tetraamminedichlorido’. The central atom iron has +3 charge (as Cl atoms carry -1 charge each and NH₃ atoms carry no charge). So the name stands as:

tetraamminedichlorido iron(III)chloride