Organometallic Chemistry Question Set-II

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Section-I (1 mark)

Q1. The electron count for the below complex is

(a) 16 e (b) 17 e (c) 18 e (d) 19 e

Q2. Addition of homonuclear systems into metal complex is going via

(a) cis-addition (b) trans-addition (c) cis & trans-reversible (d) only trans-addition

2- Q3. The formal oxidation state of Fe in [Fe(NO)(CN)5] is

(a) 1 (b) 2 (c) 3 (d) 0

Q4. Among the following, the unstable carbonyl species is:

- + (a) Mn(CO)5Cl (b) [Mn(CO)5] (c) [Mn(CO)5] (d) Mn(CO)5

Q5. In Co2(CO)8, the total number of metal-metal (CoCo) bonds are

(a) 0 (b) 1 (c) 2 (d) 3

Q6. The value of x in Fe3(CO)x :

(a) 8 (b) 9 (c) 10 (d) 12

Q7. The reaction

[(CO)5Mn(Me)] + CO > [(CO)5Mn(C(O)Me)] is an example for :

(a) Oxidative addition (b) electrophilic substitution (c) nucleophilic substitution (d) migratory insertion

Q8. The following reaction

Co2(CO)8 + H2 > 2[Co(H)(CO)4] is:

(a) oxidative addition (b) reductive elimination (c) insertion (d) addition

Q9. During the migratory insertion, the formal oxidation state of metal is increased by:

(a) +1 (b) +2 (c) -2 (d) no change Q10. Which one is the Wilkinson’s catalyst?

(a) Square planar of (PPh3)3RhCl (b) Tetrahedral of (PPh3)2RhCl2

Section-II (2 marks)

Q11. The complex:

obeys the 18e- rule. The two ‘M’ fulfilling the conditions are:

+  (a) Mo, V (b) Cr, Re (c) V, Re (d) Cr, V

Q12. The organometallic compound W(C5H5)2(CO)2 follows the 18-electron rule. The hapticities of two cyclopentadienyl groups are:

(a) 5 and 5 (b) 3 and 5 (c) 3 and 3 (d) 1 and 5

Q13. Oxidative addition of O2 to Ir(CO)Cl(PPh3)2, the oxidation state and coordination number of Ir changes respectively by

(a) 1 and 3 (b) 2 and 2 (c) 3 and 1 (d) 2 and 3

Q14. The order of reactivity of alkyl halide towards oxidative addition is:

(a) RCl > RBr > RI (b) RBr > RCl > RI (c) RI > RCl > RBr (d) RI > RBr > RCl

Q15. [Ru(C2H5)Cl(PPh3)3] is stable only under a pressure of ethene because :

(a) it is a 16-electron complex (b) it forms an 18-electron adduct with ethene (c) one of the decomposition products is ethene (d) it prevents -elimination of ethene

Q16. In the following ligand substitution reaction, propose the intermediate:

(a)

(b)

(c)

(d) Q17. Write the major and minor products in the following reaction:

(a)

(b)

(c)

(d) Q18. What is the name of the following reaction and which catalyst has been used?

(a) Cativa process; Rh-cat. (b) Wilkinson reaction; Rh-cat. (c) Monsanto process; Rh-cat. (d) Wacker reaction; Pd-cat.

 Q19. The reaction of [Cp2TaMe2]I (Cp=C5H5 ) with NaOMe will produce:

(a) Cp2Ta=CH2 (b) [Cp2Ta(OMe)2]I

Q20. Write the product using Schrock’s molybdenum catalyst:

(a)

(b)

(c)

(d)

Section-III (2 marks)

Q21. Write the formal oxidation state and number of d-electrons in Cr metal for both A and B:

(a) A: +1, 3d5 ; B: +3, 3d3

(b) A: +1, 3d3 ; B: +3, 3d1

(d) A: +3, 3d3 B: +3, 3d3

Q22. Write the intermediate A.

(a)

(b)

(c)

(d)

Q23. It will undergo dissociation reaction to give (PR3)(CO)4Mo (16 electron). What will be the order for a dissociative mechanism?

(a) PMe2Ph < PMePh2 < PPh3 < PCy3

(b) PCy3 < PMe2Ph < PMePh2 < PPh3 (c) PCy3 < PPh3 < PMePh2 < PMe2Ph (d) PMePh < PMe2Ph < PPh3 < PCy3

Q24. Replacing PPh3 by PEt3 in Wilkinson’s catalyst results in an inactive catalyst, because:

(a) The ligand association becomes very difficult due to stronger Rh-PEt3 bond. (b) The ligand dissociation becomes very difficult due to stronger Rh-PEt3 bond. (c) The oxidative addition becomes very difficult due to PEt3 ligand. (d) The reductive elimination becomes very difficult due to PEt3 ligand.

Q25. In the following ligand substitution reaction, propose the intermediates A and B:

(a)

(b)

(a) (b) (c) (d)

Q27. The hydroformylation of 1-hexene is catalysed by the cobalt catalyst Co2(CO)8. If partial pressure of CO is increased above of a certain threshold, the rate of the reaction:

(a) increases (b) decreases (c) same (d) produces side products

Q28. The rate of hydrogenation reaction using Wilkinson’s catalyst changes with alkene substitution:

(a)

(b)

(c)

(d) Q29. Write the correct conformer of the product of the hydrogenation reaction:

(a)

(b)

(c)

(d) Q30. What are the products formed in the following reaction?

(a)

(b)

(c)

(d)