3.2.5.3 Ligand Substitution and Stability

• Transition metal complexes are formed when a transition metal ion binds to one or more ligands
• The coordination number of a transition metal complex refers to the number of ligands
• The complex [Cu(NH3)4]2+ is more stable than [Cu(H2O)6]2+ because NH3 is a stronger
• Match the factors affecting stability with their effects:

  Ligand strength ↔️ Stronger ligands increase stability

  Chelate effect ↔️ Forms multiple bonds, increasing stability

  Coordination number ↔️ Higher coordination number increases stability
• Arrange the factors affecting the rate of ligand substitution in order of their effect:

  1️⃣ Ligand strength

  2️⃣ Metal ion properties

  3️⃣ Steric effects

  4️⃣ Reaction conditions
• The rate of ligand substitution is influenced by the nature of the ligands
• Which metal ion properties affect ligand substitution rates?

  Size, charge, d-electron configuration
• Stronger ligands displace weaker ligands faster in substitution reactions.


  True
• What is the central atom in a transition metal complex?

  Transition metal ion
• Which type of ligands create more stable complexes than monodentate ligands?

  Chelating ligands
• How does ligand strength affect the rate of substitution?

  Stronger ligands react faster
• What is the effect of steric effects on ligand substitution rates?

  Bulky ligands slow down substitution
• In the reaction [Cu(H2O)6]2+ + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 4H2O, the stronger ligand NH3 replaces H2O.
• Complexes with higher coordination numbers are generally more stable.
• The chelate effect arises from the increased entropy and enthalpy associated with the formation of chelate rings.
• What are two factors that contribute to the chelate effect?

  Entropy and enthalpy
• Stronger ligands like CN- and NH3 form more stable complexes than water.

  True
• Match the factor with its effect on the substitution rate:

  Ligand Strength ↔️ Stronger ligands react faster

  Metal Ion Properties ↔️ Influence reaction rates
• Stronger ligands create more stable coordinate covalent bonds in complexes.


  True
• In which chemical application is the chelate effect particularly significant?

  Selective catalysis
• Match the properties of transition metal complexes and ligands:

  Transition Metal Complexes ↔️ Compounds formed by a transition metal ion

  Ligands ↔️ Molecules or ions that donate electron pairs
• Arrange the following factors in order of their effect on the stability of a transition metal complex:

  1️⃣ Ligand strength

  2️⃣ Chelate effect

  3️⃣ Coordination number
• Ligands form coordinate covalent bonds with the central metal ion in a complex.


  True
• In ligand substitution, stronger ligands replace weaker ligands to form more stable complexes.


  True
• What is the driving force for ligand substitution reactions?

  Relative stability
• Stronger ligands react faster in ligand substitution reactions.


  True
• What is the role of steric effects in ligand substitution reactions?

  Slows down the reaction
• Ligands donate electron pairs to the transition metal ion, forming coordinate covalent bonds.
• The coordination number refers to the number of ligands bonded to the transition metal ion.
• The driving force for ligand substitution is the relative stability of the initial and final complexes.
• Match the factors with their effects on ligand substitution reactions:

  Ligand Strength ↔️ Stronger ligands displace weaker ligands

  Metal Ion Properties ↔️ Influence reaction rates

  Steric Effects ↔️ Slows down the reaction
• Which factor has the greatest effect on ligand substitution rates?

  Ligand Strength
• What is the chelate effect and why does it enhance stability?

  Multiple bonds increase entropy and enthalpy
• Chelating ligands create more stable complexes than monodentate ligands.


  True
• Stronger ligands donate electron pairs to the metal ion to create more stable coordinate covalent bonds.


  True
• The stability and kinetics of ligand substitution reactions are closely related to the strength of the ligands involved.
• Stronger ligands displace weaker ligands faster in substitution reactions.


  True
• Why does NH3 displace H2O faster in ligand substitution reactions?

  NH3 is stronger
• Match the complex with its stability and application:

  [Cu(H2O)6]2+ ↔️ Low stability, aqueous solutions

  [Cu(NH3)4(H2O)2]2+ ↔️ Moderate stability, controlled catalysis

  [Cu(en)2(H2O)2]2+ ↔️ High stability, selective catalysis
• Ligands donate electron pairs to the transition metal ion to form coordinate covalent bonds.

  True