The decreasing order of backbonding is

[Ir(CO)6]3+ < [Mn(CO)6]+ < [Cr(CO)6] < [V(CO)6]- < [Ti(CO)6]2-

[Ti(CO)6]2-< [V(CO)6]- < [Cr(CO)6] < [Mn(CO)6]+ < [Ir(CO)6]3+

[V(CO)6]- < [Ti(CO)6]2-< [Cr(CO)6] < [Ir(CO)6]3+ < [Mn(CO)6]+

[V(CO)6]- < [Ti(CO)6]2-< [Cr(CO)6] < [Mn(CO)6]+< [Ir(CO)6]3+

In the linear complex, (CO) – M – (CO) group, one of the CO group is replaced by Et3N. Choose the correct statement that is related to the above substitution reaction

υCO decreases because Et3N is not a pi-acid ligand

υCO increases because Et3N is a pi-acid ligand

υCO decreases because Et3N is a pi-acid ligand

υCO increases because Et3N is not a pi-acid ligand

[η5-Cp2Fe2(CO)3] is an 18 electron compound and shows single band at 1785 cm-1. Choose the statement from the following which describes its correct structure

There are no terminal CO groups and the complex contains Fe-Fe double bond

There are no bridging CO groups and the complex contains Fe-Fe double bond

There are 2 terminal and 1 bridging CO groups and the complex contains Fe-Fe double bond

There are 1 terminal and 2 bridging CO groups and the complex contains Fe-Fe double bond

Metal Carbonyls (G & E)

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| By Amirthachemistry

Amirthachemistry

Community Contributor

Quizzes Created: 1 | Total Attempts: 187

Questions: 8 | Attempts: 187 | Updated: Mar 18, 2023

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The test is for 15 marks and duration of the test is 20 minutes

Questions and Answers

1.

The complex, [η⁴-C₄H₄)₂M₂(CO)₃] obeys 18 electron rule and there is a triple bond between the metal atoms. Identify M from first row transition series
- A.
  
  Cr
- B.
  
  Fe
- C.
  
  Co
- D.
  
  Ni
Correct Answer
B. Fe

Explanation
The complex, [(η4-C4H4)2M2(CO)3], obeys the 18 electron rule, which means that it has a total of 18 valence electrons. Since there is a triple bond between the metal atoms, each metal atom contributes 3 electrons to the complex. This means that the remaining 12 electrons must come from the ligands. In the given options, only Fe (iron) has an atomic number that allows for the formation of a complex with 18 valence electrons. Therefore, Fe is the correct answer.

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2.

V(CO)₆ readily reacts with Na to give Na[V(CO)₆] because V(CO)₆ is an 18-electron complex
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
The given statement is false. V(CO)6 does not readily react with Na to give Na[V(CO)6]. V(CO)6 is not an 18-electron complex.

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3.

[η⁵-CpM(CO)₃]₂ obeys 18 electron rule and has one M-M bond. M could be
- A.
  
  Mn(I), Cr(0)
- B.
  
  Cr(0), Fe(I)
- C.
  
  Ti(-I), Fe
- D.
  
  Ti (0), Fe
Correct Answer
A. Mn(I), Cr(0)

Explanation
The complex [η5-CpM(CO)3]2 has a total of 18 valence electrons, which satisfies the 18 electron rule. Additionally, it has one M-M bond, indicating that the metal M is present in two oxidation states. The only combination of metal oxidation states that satisfies both of these conditions is Mn(I) and Cr(0). Therefore, Mn(I) and Cr(0) are the possible options for M in this complex.

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4.

The decreasing order of backbonding is
- A.
  
  [Ti(CO)₆]^2-< [V(CO)₆]^- < [Cr(CO)₆] < [Mn(CO)₆]⁺ < [Ir(CO)₆]³⁺
- B.
  
  [V(CO)₆]^- < [Ti(CO)₆]^2-< [Cr(CO)₆] < [Ir(CO)₆]³⁺ < [Mn(CO)₆]⁺
- C.
  
  [Ir(CO)₆]³⁺ < [Mn(CO)₆]⁺ < [Cr(CO)₆] < [V(CO)₆]^- < [Ti(CO)₆]^2-
- D.
  
  [V(CO)₆]^- < [Ti(CO)₆]^2-< [Cr(CO)₆] < [Mn(CO)₆]⁺< [Ir(CO)₆]³⁺
Correct Answer
C. [Ir(CO)₆]³⁺ < [Mn(CO)₆]⁺ < [Cr(CO)₆] < [V(CO)₆]^- < [Ti(CO)₆]^2-

Explanation
The correct answer is [Ir(CO)6]3+ < [Mn(CO)6]+ < [Cr(CO)6] < [V(CO)6]- < [Ti(CO)6]2-. This is because backbonding strength decreases as the oxidation state of the metal center increases. In this case, [Ir(CO)6]3+ has the highest oxidation state and therefore the weakest backbonding, while [Ti(CO)6]2- has the lowest oxidation state and the strongest backbonding.

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5.

In the linear complex, (CO) – M – (CO) group, one of the CO group is replaced by Et₃N. Choose the correct statement that is related to the above substitution reaction
- A.
  
  υ_CO increases because Et3N is a pi-acid ligand
- B.
  
  υ_CO decreases because Et3N is a pi-acid ligand
- C.
  
  υ_CO increases because Et3N is not a pi-acid ligand
- D.
  
  υ_CO decreases because Et3N is not a pi-acid ligand
Correct Answer
D. υ_CO decreases because Et3N is not a pi-acid ligand

Explanation
The correct statement is that υCO decreases because Et3N is not a pi-acid ligand. This is because Et3N is a Lewis base and not a pi-acid ligand. In the given linear complex, the CO ligands are pi-acceptor ligands, meaning they accept electron density from the metal center. When one of the CO ligands is replaced by Et3N, which is not a pi-acid ligand, it does not have the ability to accept electron density from the metal center like the CO ligands do. Therefore, the overall electron density around the metal center decreases, leading to a decrease in υCO.

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6.

[η⁵-Cp₂Fe₂(CO)_³] is an 18 electron compound and shows single band at 1785 cm^-1. Choose the statement from the following which describes its correct structure
- A.
  
  There are no bridging CO groups and the complex contains Fe-Fe double bond
- B.
  
  There are no terminal CO groups and the complex contains Fe-Fe double bond
- C.
  
  There are 2 terminal and 1 bridging CO groups and the complex contains Fe-Fe double bond
- D.
  
  There are 1 terminal and 2 bridging CO groups and the complex contains Fe-Fe double bond
Correct Answer
B. There are no terminal CO groups and the complex contains Fe-Fe double bond

Explanation
The presence of a single band at 1785 cm-1 indicates the absence of terminal CO groups. Additionally, the complex contains an Fe-Fe double bond.

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Current Version
Mar 18, 2023

Quiz Edited by
ProProfs Editorial Team
Jul 16, 2020

Quiz Created by
Amirthachemistry

Metal Carbonyls (G & E)

The complex, [η4-C4H4)2M2(CO)3] obeys 18 electron rule and there is a triple bond between the metal atoms. Identify M from first row transition series

V(CO)6 readily reacts with Na to give Na[V(CO)6] because V(CO)6 is an 18-electron complex

[η5-CpM(CO)3]2 obeys 18 electron rule and has one M-M bond. M could be

The decreasing order of backbonding is

In the linear complex, (CO) – M – (CO) group, one of the CO group is replaced by Et3N. Choose the correct statement that is related to the above substitution reaction

[η5-Cp2Fe2(CO)3] is an 18 electron compound and shows single band at 1785 cm-1. Choose the statement from the following which describes its correct structure

The complex, [η⁴-C₄H₄)₂M₂(CO)₃] obeys 18 electron rule and there is a triple bond between the metal atoms. Identify M from first row transition series

V(CO)₆ readily reacts with Na to give Na[V(CO)₆] because V(CO)₆ is an 18-electron complex

[η⁵-CpM(CO)₃]₂ obeys 18 electron rule and has one M-M bond. M could be

In the linear complex, (CO) – M – (CO) group, one of the CO group is replaced by Et₃N. Choose the correct statement that is related to the above substitution reaction

[η⁵-Cp₂Fe₂(CO)_³] is an 18 electron compound and shows single band at 1785 cm^-1. Choose the statement from the following which describes its correct structure