Reactions of Organometallic Compounds | MCQs for CSIR NET & GATE - Download PDF

Reactions of OGMCs
MCQs for CSIR NET & GATE

Organometallic Compounds
Topic wise Assignment-4

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Q1. Oxidation occurs very easily in case of

[NET June 2011]

(a) (n⁵-C₅H₅)₂Fe
(b) (n⁵-C₅H₅)₂Co
(c) (n⁵-C₅H₅)₂Ru
(d) (n⁵-C₅H₅)₂Co⁺

Q2. The oxidative addition and reductive elimination steps are favored by

[NET June 2011]

(a) Electron rich metal centres.
(b) Electron deficient metal centres.
(c) Electron deficient & electron rich metal centres respectively.
(d) Electron rich & electron deficient metal centres respectively.

Q3. Identify the order according to increasing stability of the following organometallic compounds, TiMe₄, Ti(CH₂Ph)₄, Ti(i-Pr)₄ and TiEt₄.

[NET June 2011]

(Me= methyl, Ph= Phenyl, i-Pr= iso-Propyl, Et= Ethyl)
(a) Ti(CH₂Ph)₄ < Ti(i-Pr)₄ < TiEt₄ < TiMe₄
(b) TiEt₄ < TiMe₄ < Ti(i-Pr)₄ < Ti(CH₂Ph)₄
(c) Ti(i-Pr)₄ < TiEt₄ < TiMe₄ < Ti(CH₂Ph)₄
(d) TiMe₄ < TiEt₄ < Ti(i-Pr)₄ < Ti(CH₂Ph)₄

Q4. Reaction of Fe(CO)₅ with OH^- leads to complex A which on oxidation with MnO₂ gives B. Compounds A and B respectively are

[NET Dec 2011]

(a) [HFe(CO)₄]^- and Fe₃(CO)₁₂
(b) [Fe(CO)₅(OH)]- and Fe₂(CO)₉
(c) [Fe(CO)₄]^2- and Mn₂(CO)₁₀
(d) [HFe(CO)₄]^- and Fe₂O₃

Q5. The greater stability of ((CH₃)₃C-CH₂-)₄Ti (A) compared to ((CH₃)₂CH-CH₂-)₄Ti (B) is due to

[NET Dec 2011]

(a) Hyperconjugation present in complex A.
(b) β-hydride elimination is not possible in complex A.
(c) Steric protection of titanium from reactive species in complex A.
(d) The stronger nature of Ti-C bond in complex A.

Q6. A compound A having the composition FeC₉H₈O₃ shows one signal at 2.5 ppm and another one around 5.0 ppm in it’s ¹H NMR spectrum. The IR spectrum of this compound shows two bands around 1900 cm^-1 and 1680 cm^-1. The compound follows the 18 electrons rule of the following statements for A, the correct one is/are

[NET Dec 2011]

(A) it has n⁵Cp group.
(B) it has a terminal CO ligand.
(C) it has a CH₃ ligand.
(D) it has Fe-H bond.
(a) A and B only
(b) C only
(c) A and C only
(d) B and D only

Q7. The reactions of Ni(CO)₄ with the ligand L (L= PMe₃ or P(OMe)₃)L yields Ni(CO)₃ L. The reaction is

[NET June 2012]

(a) Associative
(b) Dissociative
(c) Interchange (Ia)
(d) Interchange (Id)

Q8. The final product of the reaction [Mn(CO)₆]⁺ + MeLi → is

[NET June 2012]

(a) [Mn(CO)₆]⁺ Me^-
(b) [Mn(CO)₅Me]
(c) [Mn(CO)₆]
(d) [(MeCO)Mn(CO)₅]

Q9. The reaction 3[Rh₄(CO)₁₂] → 2[Rh₆(CO)₁₆] + 4CO [25 ^oC, 500 atm CO] is:

[NET June 2012]

(a) exothermic as more metal metal-metal bonds are formed.
(b) endothermic as stronger metal-carbonyl bonds are cleaved while weaker metal-metal bonds are formed.
(c) is entropically favorable but enthalpically unfavorable such that ΔG=0
(d) thermodynamically unfavorable (ΔG > 0)

Q10. In [Mo₂(S₂)₆]^2- cluster the number of bridging S₂^2- and coordination number of Mo respectively, are

[NET Dec 2012]

(a) 2 and 8
(b) 2 and 6
(c) 1 and 8
(d) 1 and 6

Q11. The substitution of n⁵Cp group with nitric oxide is the easiest for

[NET Dec 2012]

(a) n⁵Cp₂Fe
(b) n⁵Cp₂CoCl
(c) n⁵Cp₂Ni
(d) n⁵Cp₂Co

Q12. Which one of the following will NOT undergo oxidative addition by methyl chloride?

[NET Dec 2012]

(a) [Rh(CO)₂I₂]^-
(b) [Ir(PPh₃)₂(CO)Cl]
(c) [n⁵CpRh(CO)₂]
(d) [n⁵Cp₂Ti(Me)Cl]

Q13. The reaction, [(CO)₅MnMe] + CO → [(CO)₅Mn{C(O)Me}] is an example of

[NET June 2013]

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

Q14. The bond order of the metal-metal bond in the dimeric complex [Re₂Cl₄(PMe₂Ph)₄]⁺ is

[NET Dec 2013]

(a) 4.0
(b) 3.5
(c) 3.0
(d) 2.5

Q15. The electrophilic Ph₃C⁺ reacts with [(n⁵C₅H₅)Fe(CO)₂(CDMe₂)]⁺ to give a product A. The product A is formed because

[NET Dec 2013]

(a) Fe is oxidized
(b) alkyl is substituted with Ph₃C
(c) Fe-Ph bond is formed
(d) Alkyl is converted to alkene

Q16. Substitution of L with other ligands will be easiest for the species

[NET Dec 2013]

Q17. The compound [Re₂(Me₂PPh)₄Cl₄] (M) having a configuration of σ² π² δ² δ*² can be oxidized to M⁺ and M²⁺. The formal metal-metal order in M, M⁺ and M²⁺ respectively, are

[NET June 2014]

(a) 3.0, 3.5 and 4.0
(b) 3.0, 4.0 and 3.0
(c) 4.0, 3.5 and 3.0
(d) 3.0, 4.0 and 3.5

Q18. ¹H NMR spectrum of [(n⁵ C₅H₅Rh(C₂H₄)₂)] at -20^oC shows a typical AA ‘XX’ pattern in the olefinic region. On increasing the temperature to ~70 ^oC, the separate lines collapse into a single line which is due to

[NET June 2014]

(a) free rotation of the ethylene ligand about the metal olefin bond.
(b) intramolecular exchange between the ethylene ligands.
(c) intermolecular exchange between the ethylene ligands.
(d) change in hapticity of the cyclopentadienyl ligand.

Q19. The typical electronic configurations of the transition metal centre for oxidative addition
(a) d⁰ and d⁸
(b) d⁶ and d⁸
(c) d⁸ and d¹⁰
(d) d⁵ and d¹⁰

Q20. The rate of the reaction Ni(CO)₄ + PPh₃ → [Ni(CO)₃(PPh₃)] + CO depends on
(a) Concentration of both the reactants
(b) Concentration of Ni(CO)₄ only
(c) Concentration of PPh₃ only
(d) The steric bulk of PPh₃

Answer Key:

Q1.b Q2.d Q3.c Q4.a Q5.b Q6.a Q7.b Q8.d Q9.b Q10.a Q11.c Q12.d Q13.d Q14.b Q15.d Q16.c Q17.a Q18.a Q19.c Q20.b

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