Starter

1) Draw [Cu(EDTA)]2-

1) Draw the two optical isomers of [Co(H2O)2(NH2CH2CH2NH2)2]2+

edta

L.O.:

Describe the process of ligand substitution.

Describe examples of ligand substitution using [Cu(H2O)6]2+ and [Co(H2O)6]2+ with ammonia and chloride ions.

Common ligand substitution reactions

Reaction No.

Aqueous complex Complex with substituted ligands

1 [ Cu(H2O) 6]2+ (aq) Pale blue solution

[Cu(NH3) 4(H2O) 2]2+ (aq)Deep blue solution

2 [ Cu(H2O) 6]2+ (aq) Pale blue solution

[CuCl 4]2- (aq)Yellow solution

3 [ Co(H2O) 6]2+ (aq) Pink solution

[CoCl 4]2- (aq)Blue solution

Ligand substitution and equilibria

Looking at the table you have just drawn, describe and explain would happen to the position of the equilibrium if:

1.You increased the amount of HCl you added to no. 2

2.You added more water to no. 1.3.If the forward reaction in no. 2 was

exothermic and you heated the solution.4.EXTENSION: You added EDTA to number 3.

The Haem group in Haemoglobin (Hb)

Iron and the heme prosthetic group

How the haem group binds to the heamoglobin protein

The Haem group

• The iron (II) ion forms four bonds with the haem group, one with the O2 and another with the protein part of the Hb

• The coordinate bond with the O2 is a temporary bond and allows Hb to acts as a transporter molecule

• However, CO can bind instead of O2 and it does so irreversibly, rendering the haem molecule it is bound to unable to carry oxygen

Equilibrium constant, Kc

• For each of the three equilibriums in your table write out the expression for the equilibrium constant

Stability constant

• For equilibriums involving complexes we use the term stability constant instead (Kstab)

• A large Kstab means that the complex is very stable, and so suggests that the ion is very easily formed

• NB: We usually do not include water in the stability constant because usually it is such excess that its concentration effectively remains the same throughout.

Writing the units to Kstab

• Worked out in just the same way as in Kc

• Work out the units for each of the Kstab

expressions you have worked out