M.Sc. (Semester-II) Examination, 2018 CHEMISTRY [ First Paper ] ( Inorganic Chemistry )

M.Sc. (Semester-II) Examination, 2018

CHEMISTRY

[ First Paper ] ( Inorganic Chemistry )

[ CH-201 ]

Time: Three Hours
Maximum Marks: 70

Note: Answer five questions in all. Question No. 1 is compulsory. Additionally, attempt one question from each Unit.

1. Write short notes on the following: [3x10=30]

(a) Derive the relationship between stepwise and overall formation constants of metal complexes.

(b) Discuss the structures of Ru₆Cl(CO)₁₇ and Cu₂(RCOO)₄·2H₂O.

(c) Explain the lability and inertness of octahedral complexes based on Valence Bond Theory (VBT) or Crystal Field Theory (CFT).

(d) What is the difference between the acid hydrolysis of Cis-[Co(en)₂ClOH]⁺ and Trans-[Co(en)₂ClNO₂]⁺ complex ions?

(e) Write a note on the "Franck-Condon Principle" in electron transfer between metal complexes.

(f) Discuss Wade's rule for predicting the structures of metal clusters, giving an example.

(g) Give the reaction between diethylberyllium with TMEDA (tetramethylethylenediamine) and tetramethyltetrazine.

(h) Why is [M(CH₂SiMe₃)ₙ] more stable than [M(CH₂CMe₃)ₙ]?

(i) Explain why Cr(III) octahedral organometallic complexes are more stable than similar Mn(III) or V(III) complexes.

(j) How many fundamental vibrational frequencies are expected to be observed in the IR absorption spectra of an H₂O molecule? Show all IR-active vibrational modes for the H₂O molecule diagrammatically.

UNIT-I

2. (a) How does the nature of the metal cation affect the stability of metal complexes? [5]

(b) Explain the reason for the stability of chelate complexes with special reference to their thermodynamic origin, giving examples. [5]

3. (a) Discuss low nuclearity and high nuclearity in carbonyl cluster compounds. [4]

(b) Classify the structural types of the following compounds and draw their structures: [6]

(i) 1,7-C₂B₁₀H₁₂
(ii) B₅H₁₁
(iii) [Fe(C₂B₉H₁₁)₂]²⁻

UNIT-II

4. (a) Discuss the outer sphere and inner sphere mechanisms of electron transfer reactions. [5]

(b) Why is the electron transfer reaction in the [Co(NH₃)₆]²⁺ / [Co(NH₃)₆]³⁺ system slower than in the [Fe(CN)₆]³⁻ / [Fe(CN)₆]⁴⁻ system? [5]

5. (a) Discuss in detail the mechanism for the following reaction: [7]

$[Co(en)₂NH₃Cl]^{2+} + OH⁻ \rightarrow [Co(en)₂NH₃OH]^{2+} + Cl⁻$

(b) Why does the rate of the above reaction decrease upon the addition of H₂O₂? [3]

UNIT-III

6. (a) Discuss the nature of bonding in metal carbonyls. [5]

(b) Arrange the following in order of increasing C-O bond order, giving reasons: [3]

$[Ni(CO)₄], [Co(CO)₄]⁻, [Fe(CO)₄]²⁻$

(c) Explain the stability of square planar organometallic complexes of Ni(II), even though these complexes do not obey the 18-electron rule. [2]

7. (a) Discuss the rate of reactivity of organoberyllium compounds with N, O, S, and P donors. [4]

(b) Explain the M-C bond cleavage reaction in transition metal alkyls. [3]

(c) Why are σ-bonded organometallic compounds of transition metals less stable compared to their main group analogues? [3]

UNIT-IV

8. (a) Discuss microwave spectroscopy and provide the selection rule for rotational spectra of a molecule. [5]

(b) The first line corresponding to $J = 0$ appears at 3.84235 cm⁻¹ in the rotational spectrum of the ¹²C¹⁶O molecule. Calculate its moment of inertia and bond length. [5]
$h = 6.626 \times 10^{-27} \, \text{erg sec}, \, N = 6.022 \times 10^{23}$

9. (a) Discuss the application of IR spectra in elucidating the structure and properties of polyatomic molecules. [5]

(b) Explain why, in the IR spectrum of the CO₂ molecule, only two absorption bands at 2349 cm⁻¹ and 667 cm⁻¹ are observed. [5]

Discuss the factors that affect band positions and intensities in the IR region.

M.Sc. (Semester-II) Examination, 2018 CHEMISTRY [ First Paper ] ( Inorganic Chemistry )