5.5.2 Ligand substitution reactions

• The stability constant (K) measures the equilibrium constant for the formation of the complex
• In the substitution of [Fe(H₂O)₆]³⁺ by NH₃, which ligand is displaced?

  H₂O
• What type of intermediate is formed in the associative mechanism of ligand substitution reactions?

  7-coordinate
• Strong field ligands favor associative substitution due to their ability to form stable complexes.


  True
• Match the ligand strength with an example:

  Strong Field ↔️ CN⁻

  Weak Field ↔️ Cl⁻
• Ligand substitution reactions can occur through two main pathways: associative and dissociative.


  True
• In the associative mechanism, the incoming ligand first forms a 7-coordinate intermediate.
• What two factors determine which pathway a ligand substitution reaction follows?

  Ligand field strength and stability constants
• Stronger ligands increase the rate of ligand substitution reactions.


  True
• Arrange the following factors in order of their effect on reaction rate:

  1️⃣ Ligand Strength

  2️⃣ Concentration

  3️⃣ Temperature

  4️⃣ Steric Hindrance
• In the associative mechanism, the rate-determining step involves the formation of the 7-coordinate intermediate.
• Strong field ligands and high coordination numbers favor the associative mechanism.


  True
• Match the term with its definition:

  Ligand Exchange ↔️ One ligand displaces another

  Stability Constant (K) ↔️ Measures equilibrium for complex formation
• CN⁻ and NH₃ are examples of strong field ligands.


  True
• In the substitution reaction of [Fe(H₂O)₆]³⁺ by NH₃, the stronger field ligand NH₃ displaces H₂O.
• In a ligand substitution reaction, a stronger field ligand replaces a weaker field ligand.

  True
• Strong field ligands favor associative substitution mechanisms.


  True
• What effect does steric hindrance have on the rate of ligand substitution reactions?

  Decreases it
• Dissociative mechanisms create a 5-coordinate intermediate.


  True
• What is the key difference between cis and trans isomers in coordination complexes?

  Ligand arrangement
• Smaller ligands in a coordination complex favor the formation of the cis isomer due to lower steric hindrance.


  True
• What is a ligand substitution reaction?

  Ligand replacement in a complex
• Strong field ligands such as CN⁻ and NH₃ are examples of ligands that bind tightly to metal ions.


  True
• NH₃ displaces H₂O in [Fe(H₂O)₆]³⁺ because it has a stronger field strength.


  True
• In the dissociative mechanism, the leaving ligand first creates a 5-coordinate intermediate
• Steps in the associative mechanism of ligand substitution reactions

  1️⃣ Incoming ligand associates with the complex

  2️⃣ 7-coordinate intermediate is formed

  3️⃣ Rearrangement to expel the leaving ligand
• What does a higher stability constant indicate about a ligand's binding strength?

  Stronger binding strength
• The dissociative mechanism involves the formation of a 5-coordinate intermediate.


  True
• The stability constant (K) measures the equilibrium constant for complex formation.
• How does higher concentration of both the complex and incoming ligand affect the reaction rate?

  Increases reaction rate
• Why do larger ligands reduce the reaction rate of ligand substitution reactions?

  Increased steric hindrance
• What is the rate-determining step in the dissociative mechanism?

  Ligand dissociation
• A ligand substitution reaction involves the replacement of one ligand by another in a coordination complex.
• What does the stability constant (K) indicate about ligand binding?

  Strength of ligand binding
• What are examples of weak field ligands?

  H₂O and Cl⁻
• Which ligand is an example of a strong field ligand?

  CN⁻
• A ligand substitution reaction is governed by the relative strengths of the ligands
• The stability constant (K) measures the equilibrium constant for complex formation
• Steps in the associative mechanism of ligand substitution

  1️⃣ Incoming ligand associates

  2️⃣ Forms a 7-coordinate intermediate

  3️⃣ Rearrangement expels the leaving ligand
• Match the isomer type with its stability:

  Cis ↔️ Lower stability

  Trans ↔️ Higher stability