Tetrahedral Coordination - Inorganic Chemistry - Exam, Exams for Inorganic Chemistry. Aliah University
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Tetrahedral Coordination - Inorganic Chemistry - Exam, Exams for Inorganic Chemistry. Aliah University

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Tetrahedral Coordination, Stabilisation Energy, Crystal Field, Associative and a Dissociative, Metal Complex, Law for the Hydrolysis, Presence of Base, Mechanism, Structures of the Reaction, Active Metal Centre. This is ...
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Microsoft Word - CH319_BPC_2010_2011.doc

Spring Examinations 2010 / 2011

Exam Code(s) 3BPC2

Exam(s)

Module Code(s) CH319 Inorganic Chemistry

Module(s)

Paper No. I

External Examiner(s) Professor K. Molloy

Internal Examiner(s) Dr. A. Erxleben, Dr. T. Higgins , Dr. L. Jones

Instructions:

Answer four questions. Answer at least one question from each section. All questions carry 25 marks distributed as shown. Leave the first page of

the Answer Book blank and list on it clearly the numbers of the questions

attempted.

Duration

2 hrs

No. of Pages 3 Following this page

Discipline(s) Chemistry

Requirements log tables with periodic table

Section A Answer at least one question from this section

1. Answer each of the following: (a) Describe the crystal field splitting patterns for (i) octahedral, (ii) tetrahedral

geometries. [5 marks] (b) Calculate the crystal field stabilisation energy (in terms of 10Dq) for high spin

octahedral and for tetrahedral coordination compounds of the following ions Cr(III), Mn(III), Co(II), and Fe(III). [8 marks]

(c) Identify the range of factors that influence whether a transition metal coordination

compound will exhibit octahedral or tetrahedral geometry. [4 marks] (d) For each of the following ions give the formula of a compound that you predict

will exhibit (i) tetrahedral, and (ii) octahedral geometry: Cr(III), Mn(III), Co(II), and Fe(III). [8 marks]

2. Answer each of the following: (a) Draw crystal field splitting patterns for the octahedral ions [Cr(NH3)6]3+ and

[Cr(Cl)6]3-. [4 marks] (b) Draw fully labelled molecular orbital bonding schemes for the octahedral ions

[Cr(NH3)6]3+ and [Cr(Cl)6]3-. [10 marks] (c) Describe the π-donor nature of the bonding between chloride and metal ions. [5 marks] (d) Using the molecular orbital schemes account for the relative positions of ammonia

and chloride in the spectrochemical series. [6 marks]

more on the next page

Section B Answer at least one question from this section

3. Answer each of the following: (a) Describe the roles by calcium, and zinc in biological systems. [8 marks] (b) Describe the nature of the peptide bond and the role played by hydrogen bonding

in determining the secondary structure of proteins. [9 marks] (c) Give one example of a metallo protein that functions as a redox centre. Draw a

structure for the active metal centre and clearly identify the ligands that coordinate the metal ions. [8 marks]

4. Answer each of the following: (a) Draw the structures of the reaction products of the following reactions: (i) [PtCl3(NH3)]- + NH3 (ii) [PtCl3(CO)]- + NH3 Clearly indicatethe isomer that is formed and explain your answer in each case.

[6 marks] (b) Suggest an experiment to distinguish between an associative and a dissociative

mechanism for a ligand substitution reaction in a metal complex. [4 marks] (c) Comment on the fact that the rate constants for the following reactions are very

similar: [Co(NH3)5(H2O)]3+ + X– → [Co(NH3)5X]2+ + H2O [X = Cl–, Br–, I–, SCN–] [6 marks] (d) The rate law for the hydrolysis of [CoCl(NH3)5]2+ in the presence of base is d[CoCl(NH3)5]/dt = -kobs [CoCl(NH3)5] [OH-]. Suggest a mechanism that is consistent with this rate law. [9 marks] more on the next page

Section C Answer at least one question from this section

5. Answer each of the following: (a) For each of the following give the metal valence electron count, thus identifying

whether the 18 electron rule is obeyed in each case. Show your workings clearly. (i)[Cr(6-C6H6)(CO)3](ii) [Fe(CO)2(NO)2] (iii)[Mo(3-allyl)(4-buta-1,3-diene)(5-C5H5)](iv)[Fe(η2-buta-1,3-diene)(CO)2(PPh3)2] [10 marks]

(b) With respect to complex (ii) above, describe the bonding mode (shape) exhibited

by the nitrosyl (NO) ligand and give an alternative mode for this ligand. Produce a sketch of complex (ii) to aid your answer. The nitrosyl ligand can also bridge two transition metal centres, explain this occurrence using a suitable sketch to aid your answer. [10 marks]

(c) Draw the following hydride bonding modes when bonding to transition metal(s)

(use M as the symbol for metal centre). Which spectroscopic technique would you use to locate the presence of such hydride ligands?

(i) µ-H (ii) µ3-H (iii) Interstital µ6-H [5 marks]

6. Answer each of the following:

(a) Describe the accepted bonding scheme adopted by a carbon monoxide ligand (CO) when bonded to a transition metal ion. Include a sketch of the orbital interactions involved. [7 marks]

(b) The type of bonding mode adopted by a CO ligand within an organometallic

complex can be deduced via Infra-Red spectroscopy. Using your answer in (a), explain this relationship using diagrams to aid you answer. [8 marks]

(c) Explain the concept of oxidative addition in terms of the reaction of Vaska`s

complex with CH3I. Give the metal oxidation state and metal valence electron count for all complexes described in your answer. [10 marks]

   

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