UPSC Combined Geo-Scientist, Mains · 2016 · Mains Paper I
Q1(h). Square-planar geometrical isomers
Question
Explain briefly geometrical isomerism. Draw the structures of various geometrical isomers of the following complexes: (i) [PtCl₂(NH₃)₂] (ii) [Pt(NO₂)(C₅H₅N)(NH₃)(NH₂OH)].
Answer in brief
The square-planar complexes have respectively two and three geometrical arrangements.
Key points
- Geometrical isomers have the same connectivity to the metal but different relative positions of ligands.
- For [PtCl₂(NH₃)₂], the two chlorido ligands are adjacent in the cis isomer and opposite in the trans isomer. In the sketch A=NH₃.
- For four different ligands, put a=NO₂, b=C₅H₅N, c=NH₃, d=NH₂OH. The three distinct trans-pair sets are (a,c)/(b,d), (a,b)/(c,d) and (a,d)/(b,c).
- Keep the donor atom of each ligand fixed: linkage isomerism is a different issue.
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
CoversSquare-planar geometrical isomersCoordination isomerism
All parts of Question 1
- 1(a) Occurrence of lithium5 marks
- 1(b) Bond order and ionisation5 marks
- 1(c) Solvent levelling5 marks
- 1(d) Disproportionation and its reverse5 marks
- 1(e) Interpreting the redox data5 marks
- 1(f) Existence of hydrogen and helium dimers5 marks
- 1(g) Packing fraction5 marks
- 1(h) Square-planar geometrical isomers5 marks
- 1(i) Ground term and angular momenta5 marks
- 1(j) Effective atomic number5 marks