Organometallic Compounds (18 electron rule) MCQs for CSIR NET GATE - Chem Content

18 electron Rule

MCQs for CSIR NET & GATE

Organometallic Compounds

Topic wise assignment 2

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Q1. The complex in which ligand form only σ bond with metal is

[NET June 2011]

(a) W(CH₃)₆
(b) (n5-C₅H₅)₂Fe
(c) K[PtCl₃(C₂H₄)]
(d) (n⁶-C₆H₆)₂Ru

Q2. The correct combination of metal, number of carbonyl ligands and the charge for a metal carbonyl complex [M(CO)_x]^z- that satisfies 18 electron rule is

[NET Dec 2011]

(a) M=Ti, x=6, z=1
(b) M=V, x=6, z=1
(c) M=Co, x=4, z=2
(d) M=Mo, x=5, z=1

Q3. The stable cyclopentadienyl complex of beryllium is

[NET Dec 2011]

(a) Be(n²-C₅H₅)₂
(b) Be(n²-C₅H₅)(n³-C₅H₅)
(c) Be(n¹-C₅H₅)(n³-C₅H₅)
(d) Be(n¹-C₅H₅)(n⁵-C₅H₅)

Q4. The number of metal-metal bonds in the dimers, [CpFe(CO)(NO)]₂ and [CpMo(CO)₃]₂ respectively are

[NET Dec 2011]

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

Q5. The complex that doesn't obey 18 electron rule is

[NET June 2012]

(a) [(n⁵-C₅H₅)RuCl(CO)(PPh₃)]
(b) [W(CO)₃SiMe₃(Cl)(NCMe)₂]
(c) [IrCl₃(PPh₃)₂(AsPh₂)]-
(d) [Os(N)Br₂(PMe₃)(NMe₂)]-

Q6. The following molecule obeys 18 electron rule if metal M is-

[NET Dec 2012]

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

Q7. In the cluster [Co₃(CH)(CO)₉] obeying 18 electron rule, the number of metal-metal bonds and the bridging ligands respectively are

[NET Dec 2012]

(a) 3 and 1 CH
(b) 0 and 3 CO
(c) 3 and 1 CO
(d) 6 and 1 CH

Q8. The oxidation state of Mo in [n⁷-tropylium)Mo(CO)₃]⁺ is

[NET June 2013]

(a) +2
(b) +1
(c) 0
(d) -1

Q9. The number of metal-metal bonds in [W₂(OPh)₆] is

[NET June 2013]

(a) 1
(b) 2
(c) 3
(d) 4

Q10. The number of metal-metal bonds in [Ir₄(CO)₁₂] is

[NET June 2013]

(a) 4
(b) 6
(c) 10
(d) 12

Q11. In a cluster, [H₃CoRu₃(CO)₁₂], the total electrons considered to be involved in it's formation is

[NET Dec 2013]

(a) 57
(b) 60
(c) 63
(d) 72

Q12. The oxidation state of Ni and number of metal-metal bonds in [Ni₂(CO)₆]^2- that are consistent with 18 electron rule respectively are

[NET June 2014]

(a) -2, 1
(b) +4, 2
(c) -1, 1
(d) +4, 3

Q13. Hapticities 'x' and 'y' of the arenes in the following diamagnetic complex [(n^x-C₆H₆)Ru(n^y-C₆H₆)] respectively are

[NET Dec 2014]

(a) 6 and 6
(b) 4 and 4
(c) 4 and 6
(d) 6 and 2

Q14. The binding modes of NO in 18 electron compounds [Co(CO)₃(NO)] and [Ni(n⁵-Cp)(NO)] respectively are

[NET June 2015]

(a) linear and bent
(b) bent and linear
(c) both linear
(d) both bent

Q15. The W-W bond order in [W(n⁵-C₅H₅)(µ-Cl)(CO)₂]₂ is

[Net Dec 2015]

(a) three
(b) two
(c) one
(d) zero

Q16. Identify the species obeying 18 electron rule

[NET June 2016]

(a) A and B
(b) B and C
(c) C and D
(d) A and D

Q17. The number of metal-metal bonds in [Co₂Fe₂(CO)₁₁(µ⁴-PPh)₂] is

[NET June 2016]

(a) 3
(b) 4
(c) 5
(d) 6

Q18. Heating a sample of [(n⁵-C₅H5)Mo(CO)₃]₂ complex results in the formation of [(n⁵-C₅H₅)Mo(CO)₂]₂ with elimination of 2 equivalents of CO. The Mo-Mo bond order in this reaction changes from

[NET June 2016]

(a) 2 to 3
(b) 1 to 2
(c) 1 to 3
(d) 2 to 4

Q19. The number of bridging ligands and metal-metal bonds in the following complex obeying 18 electron rule are

[Ru₂(n⁵-Cp)₂(CO)₂(Ph₂PCH₂PPh₂)]

[NET Dec 2016]

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

Ans Key

1.a 2.b 3.d 4.d 5.d 6.a 7.a 8.c 9.c 10.b 11.b 12.c 13.c 14.c 15.d 16.d 17.b 18.c 19.c

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