Bidentate and multidentate ligands 212-213

Question 1

What is a bidentate ligand?

Answer 1

A ligand that can donate two lone pairs of electrons to the central metal ion to form two coordinate bonds.

Question 2

Draw an ethanedioate ion, C₂O₄^2-, and state what type of ligand it is.

Answer 2

It is a bidentate ligand.

Question 3

Draw the cis and trans isomers of [Cr(C₂O₄)₂(H₂O)₂]^-.

Answer 3

Question 4

What is a hexadentate ligand?

Answer 4

A hexadentate ligand has six lone pairs of electrons, each forming a coordinate bond to a metal ion in a complex ion.

Question 5

Draw the full structure of EDTA when it exists in complexes as the ion EDTA^4-.

Answer 5

• Note six pairs of electrons, each of which can form a coordinate bond.

Question 6

What are the requirements for optical isomerism?

Answer 6

• A complex with three molecules or ions of bidentate ligand. [Ni(en)_3]²⁺.
• A complex with two molecules or ions of a bidentate ligand, and two molecules or ions of monodentate ligand. [Co(en)₂Cl₂].
• A complex with one hexadentate ligand - [Cu(EDTA)]^2-.

Question 7

Draw the structure of the ligand ethane-1,2-diamine. What type of ligand is it?

Answer 7

NH₂CH₂CH₂NH₂, often shortened to ‘en’.

It is a bidentate ligand, because each nitrogen atom donates a lone pair of electrons to form a coordinate bond.

Question 8

What are optical isomers?

Answer 8

Optical isomers are compounds that are non-superimposable mirror images of each other.