Ligand Substitution

Question 1

What is ligand substitution

Answer 1

When ligands in a transition metal complex are exchanges for other ligands

Question 2

Structure of haem

Answer 2

Six coordinate bonds around central Fe2+ ion, forms four coordinate bonds with nitrogen atoms and one with bond to globin protein and another with water which can easily be replaced by oxygen

Question 3

What happens when CO reacts with haemoglobin

Answer 3

Forms carboxyhaemoglobin which is more stable than the complex formed with oxygen so binds irreversibly and carrying capacity for oxygen greatly reduced leading to death

Question 4

What is the chelate effect

Answer 4

How monodentate ligands are replaced by bi/multidentate ligands as these form more stable complexes

Question 5

Why are monodentate ligands replaced by bi/multi

Answer 5

As there is an increase in delta S system as more molecules in products compared with reactants meaning delta G more negative and reaction more favourable

Question 6

Why is enthalpy change for ligand substitution very small

Answer 6

As the bonds being formed are very similar to bonds that were broken

Question 7

Which forms stronger bonds with metal ion: water or ethanedioate ions

Answer 7

Ethanedioate as overall negative charge so greater electron density and lps more available for bonding

Question 8

What is Kstab

Answer 8

Equilibrium constant for complex stability, the greater it is the greater the stability

Question 9

What can change in complex in ligand substitution

Answer 9

The shape, colour, coordination number and charge

Question 10

Equation for reaction between hexaaquacopper (II) and chloride ions and colour change

Answer 10

[Cu(H2O)6]2+ + 4Cl- ——> [CuCl4]2- + 6H2O
-from blue to yellow

Question 11

Equation and colour change for reaction between hexaaquacobalt (II) and chloride ions

Answer 11

[Co(H2O)6]2+ + 4Cl- —->[CoCl4]2- + 6H2O
-from pink to blue