Unit 1) 6) Ligands And Transition Metal Complexes

Question 1

What is a complex

Answer 1

A complex consist of a central metal ion surrounded by ligand
- an important property of transition metals is their ability to form complexes

Question 2

The molecules or ions surrounding the central metal ion or atom are called _______

Answer 2

The molecules or ions surrounding the central metal ion or atom are called ligands

Question 3

What are ligands

Answer 3

Ligands are electron donors which are usually negative ions or uncharged molecules with one or more non bonding pairs of electrons (lone pairs)

Question 4

Ligands are electron donors , what do they donate

Answer 4

• ligands are electron donors , donating their non bonding electrons into infilled metal orbitals and forming what are known as dative covalent bonds

Question 5

What is a dative covalent bond

Answer 5

A dative covalent bond is one in which both electrons in the bond are donated by one of the atoms rather than one from each atom

Question 6

What are common neutral ligands

Answer 6

Ammonia (NH3) and water (H20) are common neutral ligands .

• ammonia has a non bonding pair of electrons on the nitrogen ion
• water has two non bonding pairs on the oxygen atom

Question 7

What are common negatively charged ligands

Answer 7

Cl- and CN-

Question 8

What are monodentate ligands

- what are some examples

Answer 8

Ligands which donate one pair of electrons to the central metal ion are said to be monodentate.
- some examples Include Cl- and H20,CN- and NH3 A
(Chloride , water , cyanide and ammonia)

Question 9

What is a bidentate ligand

- include some examples

Answer 9

A bidentate ligand donates two pairs of electrons to the central metal ion

• examples include the oxalate ion (C2O4^2-) and 1,2 diaminoethane (ethylenediamine)
• look at drawings in notes

Question 10

What is a hexadentate ligand

- common example of this ligand

Answer 10

A hexadentate ligand has six pairs of non bonding electrons that bind to a central metal ion in a 1:1 ration

• a hexadentate you should be familiar with is ethylenediamineetetraacetic acid (EDTA)
• look at diagrams in notes (the diagram shows the structure if the EDTA ligand and how it forms a complex with the nickel (II)ion

Question 11

What is the charge of the EDTA ion

Answer 11

EDTA ion has a 4- charge

Question 12

What is a quadridentate ligand

Answer 12

• a quadridentate ligand has four lone pairs, so forms four co-ordinate bonds with the central metal atom or ion
• an example of this occurs in haemoglobin

Question 13

What is the coordination number

Answer 13

• the coordination number of the central transition metal ion is the number of bonds from it to the ligands

Question 14

The co ordination number will determine the ______ of the complex ion

Answer 14

The co -ordination number will determine the shape of the complex ion

Question 15

Co ordination number 2,4,6

Answer 15

2 - linear shape
4 - either square planar or tetrahedral
6- octahedral