15.1.6 - Multidentate ligands

Question 1

What is a Bidentate ligand?

Answer 1

A ligand that has 2 atoms that each use a lone pair to form a dative bond with the metal ion.

Question 2

What is the name of the most common bidentate ligand?

Answer 2

1,2- diaminoethane
en

Question 3

how does en act as a bidentate ligand?

Answer 3

The two lone pairs on the nitrogen atoms are used to form dative covalent bonds with the metal ion.

Question 4

What is the name of the most common multi dentate ligand?

Answer 4

EDTA

Question 5

How does EDTA acts as a multi dentate ligand?

Answer 5

The 4 ethanoic acid groups lose a hydrogen.
This gives COO- negative ions with lone pairs.
The nitrogen atoms also have lone pairs.
6 dative covalent bonds can be formed with metal ion.

Question 6

How many dative covalent bonds can EDTA form with a metal ion and where do the lone pairs come from?

Answer 6

6
2 from lone pairs on nitrogen atoms
4 from the oxygen of a COO group after losing a hydrogen.

Question 7

What type of ligand is water?

Answer 7

Monodentate

Question 8

What happens to the stability when a mono dentate ligand is replaced by a bidentate ligand?

Answer 8

The stability increases.

Question 9

Describe the structure inside haem groups in haemoglobin.

Answer 9

4 nitrogen atoms hold an Fe2+ ion by forming dative covalent bonds in a square planar structure.
Globin forms a dative bond.
Oxygen uses on of its lone pairs to form a dative bond.
6 dative covalent bonds in haemoglobin.

Question 10

What happens when carbon monoxide is inhaled, make reference to haemoglobin.

Answer 10

The dative covalent bond between carbon monoxide and haemoglobin is much stronger than the dative bond between oxygen and haemoglobin.
So carbon monoxide replaces the oxygen bound to haemoglobin in a ligand substitution reaction.