Chapter 5 Solutions — Coordination Compounds

Exercises

1. 1.
   Explain the bonding in coordination compounds in terms of Werner's postulates.
2. 2.
   FeSO₄ solution mixed with (NH₄)₂SO₄ solution in 1:1 molar ratio gives the test of Fe²⁺ ion but CuSO₄ solution mixed with aqueous ammonia in 1:4 molar ratio does not give the test of Cu²⁺ ion. Explain why?
3. 3.
   Explain with two examples each of the following: coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.
4. 4.
   What is meant by unidentate, didentate and ambidentate ligands? Give two examples for each.
5. 5.
   Specify the oxidation numbers of the metals in the following coordination entities:

   • (i) [Co(H₂O)(CN)(en)₂]²⁺
   • (ii) [CoBr₂(en)₂]⁺
   • (iii) [PtCl₄]²⁻
   • (iv) K₃[Fe(CN)₆]
   • (v) [Cr(NH₃)₃Cl₃]
6. 6.
   Using IUPAC norms write the formulas for the following:

   • (i) Tetrahydroxidozincate(II)
   • (ii) Potassium tetrachloridopalladate(II)
   • (iii) Diamminedichloridoplatinum(II)
   • (iv) Potassium tetracyanidonickelate(II)
   • (v) Pentaamminenitrito-O-cobalt(III)
   • (vi) Hexaamminecobalt(III) sulphate
   • (vii) Potassium tri(oxalato)chromate(III)
   • (viii) Hexaammineplatinum(IV)
   • (ix) Tetrabromidocuprate(II) (x)…
7. 7.
   Using IUPAC norms write the systematic names of the following:

   • (i) [Co(NH₃)₆]Cl₃
   • (ii) [Pt(NH₃)₂Cl(NH₂CH₃)]Cl
   • (iii) [Ti(H₂O)₆]³⁺
   • (iv) [Co(NH₃)₄Cl(NO₂)]Cl
   • (v) [Mn(H₂O)₆]²⁺
   • (vi) [NiCl₄]²⁻
   • (vii) [Ni(NH₃)₆]Cl₂
   • (viii) [Co(en)₃]³⁺
   • (ix) [Ni(CO)₄]
8. 8.
   List various types of isomerism possible for coordination compounds, giving an example of each.
9. 9.
   How many geometrical isomers are possible in the following coordination entities?

   • (i) [Cr(C₂O₄)₃]³⁻
   • (ii) [Co(NH₃)₃Cl₃]
10. 10.
    Draw the structures of optical isomers of:

    • (i) [Cr(C₂O₄)₃]³⁻
    • (ii) [PtCl₂(en)₂]²⁺
    • (iii) [Cr(NH₃)₂Cl₂(en)]⁺
11. 11.
    Draw all the isomers (geometrical and optical) of:

    • (i) [CoCl₂(en)₂]⁺
    • (ii) [Co(NH₃)Cl(en)₂]²⁺
    • (iii) [Co(NH₃)₂Cl₂(en)]⁺
12. 12.
    Write all the geometrical isomers of [Pt(NH₃)(Br)(Cl)(py)] and how many of these will exhibit optical isomers?
13. 13.
    Aqueous copper sulphate solution (blue in colour) gives:

    • (i) a green precipitate with aqueous potassium fluoride and
    • (ii) a bright green solution with aqueous potassium chloride. Explain these experimental results.
14. 14.
    What is the coordination entity formed when excess of aqueous KCN is added to an aqueous solution of copper sulphate? Why is it that no precipitate of copper sulphide is obtained when H₂S(g) is passed through this solution?
15. 15.
    Discuss the nature of bonding in the following coordination entities on the basis of valence bond theory:

    • (i) [Fe(CN)₆]⁴⁻
    • (ii) [FeF₆]³⁻
    • (iii) [Co(C₂O₄)₃]³⁻
    • (iv) [CoF₆]³⁻
16. 16.
    Draw figure to show the splitting of d orbitals in an octahedral crystal field.
17. 17.
    What is spectrochemical series? Explain the difference between a weak field ligand and a strong field ligand.
18. 18.
    What is crystal field splitting energy? How does the magnitude of Do decide the actual configuration of d orbitals in a coordination entity?
19. 19.
    [Cr(NH₃)₆]³⁺ is paramagnetic while [Ni(CN)₄]²⁻ is diamagnetic. Explain why?
20. 20.
    A solution of [Ni(H₂O)₆]²⁺ is green but a solution of [Ni(CN)₄]²⁻ is colourless. Explain.
21. 21.
    [Fe(CN)₆]⁴⁻ and [Fe(H₂O)₆]²⁺ are of different colours in dilute solutions. Why?
22. 22.
    Discuss the nature of bonding in metal carbonyls.
23. 23.
    Give the oxidation state, d orbital occupation and coordination number of the central metal ion in the following complexes:

    • (i) K₃[Co(C₂O₄)₃]
    • (ii) cis-[CrCl₂(en)₂]Cl
    • (iii) (NH₄)₂[CoF₄]
    • (iv) [Mn(H₂O)₆]SO₄
24. 24.
    Write down the IUPAC name for each of the following complexes and indicate the oxidation state, electronic configuration and coordination number. Also give stereochemistry and magnetic moment of the complex:

    • (i) K[Cr(H₂O)₂(C₂O₄)₂].3H₂O
    • (ii) [Co(NH₃)₅Cl]Cl₂
    • (iii) [CrCl₃(py)₃]
    • (iv) Cs[FeCl₄]
    • (v) K₄[Mn(CN)₆]
25. 25.
    Explain the violet colour of the complex [Ti(H₂O)₆]³⁺ on the basis of crystal field theory.
26. 26.
    What is meant by the chelate effect? Give an example.
27. 27.
    Discuss briefly giving an example in each case the role of coordination compounds in:

    • (i) biological systems
    • (ii) medicinal chemistry
    • (iii) analytical chemistry
    • (iv) extraction/metallurgy of metals.
28. 28.
    How many ions are produced from the complex Co(NH₃)₆Cl₂ in solution?

    • (i) 6
    • (ii) 4
    • (iii) 3
    • (iv) 2
29. 29.
    Amongst the following ions which one has the highest magnetic moment value?

    • (i) [Cr(H₂O)₆]³⁺
    • (ii) [Fe(H₂O)₆]²⁺
    • (iii) [Zn(H₂O)₆]²⁺
30. 30.
    Amongst the following, the most stable complex is:

    • (i) [Fe(H₂O)₆]³⁺
    • (ii) [Fe(NH₃)₆]³⁺
    • (iii) [Fe(C₂O₄)₃]³⁻
    • (iv) [FeCl₆]³⁻
31. 31.
    What will be the correct order for the wavelengths of absorption in the visible region for the following: [Ni(NO₂)₆]⁴⁻, [Ni(NH₃)₆]²⁺, [Ni(H₂O)₆]²⁺?