LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2012

CH 3809 – COORDINATION CHEMISTRY

 

 

Date : 24-04-2012             Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

Part-A

Answer all questions. Each question carries two marks:

1. The thermodynamic stability of high-spin complexes of d^0,5,10 metal ions are lower than that of other dⁿ metal ions under identical ligand framework. Comment upon this observation.
2. Identify the number of isomers of [Co(en)₂(SCN)₂]⁺.
3. It is exceedingly difficult to synthesize low-spin T_d complexes of first row transition metals. Rationalize.
4. What is nephelauxetic ratio? Mention its significance.
5. Transition metal complexes are invariably colored, while their cabonyls are mostly colorless. Offer a reasonable explanation.
6. Jahn-Teller distortion in 6-coordinate complexes of low-spin d⁴ metal ions escapes experimental detection, while it can be detected in 6-coordinate complexes of high-spin d⁴ metal ions. Explain.
7. Differentiate trans-effect and trans-influence.
8. Organometallic compounds are formed by transition metal ions in their low oxidation state. Comment.
9. What is halometallation reaction? Cite an example.
10. Mention the biological roles of the enzyme carboxy peptidase A.

Part-B

Answer eight questions. Each question carries five marks:

11. How is nitro- and nitrito complexes differentiated by IR spectroscopy?
12. State Jahn Teller theorem. Explain static dynamic Jahn Teller distortion with an example. How is it studied experimentally?
13. What is molecular recognition? Give an account of recognition of neutral molecules by molecular receptors.
14. Explain photoisomerization and photosubstitution reactions in transition metal complexes with examples.
15. Give an account of the synthesis and structural features of p-complexes of cyclooctatetraene and cycloheptatriene with transition metals.
16. Explain supramolecular assemblies formed by self assembly methods.
17. Give an account of the mechanism of substitution reactions in tetrahedral complexes.
18. What is trans-effect? You are provided with K₂PtCl₄ and ammonia. How do you synthesisecis– and trans-isomers of [PtCl₂(NH₃)₂]?
19. Explain the synthesis of Ziegler-Natta catalysts and the mechanism of polymerization of olefins by this catalyst.
20. The epr spectrum of [Cu(salen)] consists of four sets of eleven lines each. Interpret the spectrum and substantiate your result with the help of experimental evidences.
21. Write a note on copper proteins.
22. Explain the structural features and biological roles of superoxide dismutase.

Part-C

Answer four questions. Each question carries ten marks:

23a. Identify the metal orbitals and LGOs suitable for s– and p-bonding in O_h complexes of transition metal ions. Construct a qualitative MO energy level diagram for s-bonding.          (6)

1. Justify the position of CO in the spectrochemical series with the help of MO theory. (4)
2. Explain the principles of angular overlap model. Show that D_t = 4/9D_o with the help of this theory.

25a. Explain the electronic spectral features of high-spin Oh and T_d complexes of d^1-9 metal ions.                                                                                                                                                      (6)

1. Construct the Orgel diagram for high-spin d³ and d⁷O_h and T_d complexes.                  (4)

26a. Explain the mechanism of palladium chloride-catalyzed production of acetaldehyde. (4)

1. Explain the mechanism of replacement of coordinated water by another ligand in octahedral complexes.                                                                                         (6)

27a. Explain the mechanism of oxygen transport in mammalian systems.                             (7)

1. Give an account of synthetic oxygen carriers. (3)

28a. What are electron transfer reactions? Differentiate complimentary and non-complimentary electron transfer reactions with examples.                                                 (3)

1. Explain the inner- and outer-sphere mechanisms of electron transfer reactions in coordination compounds with examples. Mention the various factors which affect these mechanisms.            (7)

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – NOVEMBER 2012

CH 3809 – COORDINATION CHEMISTRY

 

 

Date : 03/11/2012            Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

 

Part – A

Answer all the questions:                                                                                                           (10 x 2 = 20)

 

1. Calculate the spin only magnetic moment of d⁴, high and low spin octahedral system.
2. Why does metal with d⁸configuration readily form square planar complexes?
3. Is MnCr₂O₄ likely to have a normal or inverse spinel structure?
4. What is the electronic configuration of [Mn(NCS)₆]^4- if the magnetic moment of complex is 6.06 Bohr magneton.
5. Why is the stretching frequency of C—O high for terminal carbonyls compared to bridging metal carbonyls?
6. Why does electronic spectra of [Ni(en)₃]²⁺ show three absorption bands?
7. Why the electron transfer reaction is slow between the complexes of [Fe(CN)₆]^4- and [Co(NH₃)₆]³⁺?
8. What is Nephelauxetic effect?
9. What is Wilkinson catalyst? Which type of reaction is easily activated by this catalyst?
10. What are the main functions of chlorophyll in photosynthesis?

Part – B

Answer any eight questions:                                                                                                     (8 x 5  = 40)

 

11. Explain the d orbital splitting of octahedral complexes using crystal field theory.
12. Write a brief note on static and dynamic JahnTeller effect.
13. What are the evidences supporting Crystal field theory? Explain with examples.
14. Which dⁿ configurations show quenching of orbital angular momentum if it forms octahedral, high and low spin complexes?
15. Derive the ground term of d⁴ and d⁵.
16. Discuss the associative and dissociative mechanisms of substitution reactions in metal complexes^.
17. Describe the mechanistic pathway of hydroformylation of alkene using catalyst.
18. How is optical rotatory dispersion study useful to determine the absolute configuration of chiral complexes?
19. What is trans effect? How is this effect helpful in synthesizing steroisomers?
20. What are supramolecular assemblies? Describe any one method to assemble such a system.
21. Explain photoaquation and photoisomerisation reactions with examples.
22. Briefly explain the role of metal ion in the hydrolytic breakdown of protein by carboxy peptidase.

 

 

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Part – C

Answer any four questions:                                                                                                        (4 x 10 = 40)

 

23. Explain with the help of MOT why Cl^– acts as a weak ligand whereas

CN^– acts as a strong ligand in octahedral transition metal complexes.

24. How is Orgel diagram helpful in explaining the electronic spectrum of d^1-9, high spin octahedral and tetrahedral complexes.
25. Discuss in detail the mechanisms of outer and inner sphere electron transfer in metal
26. a) Explain the synergic effect of metal-ligand bonding in metal carbonyls.
27. b) Explain the variations in the stretching frequency of the isoelectronic species, Cr(CO)₆, [V(CO)₆]^– and [Mn(CO)₆]⁺.
28. Discuss the bonding in ferrocene on the basis of molecular orbital energy level diagram.
29. Discuss the essential structure of haemoglobin and explain its cooperativity in its oxygenation.

 

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