1.5. Transition Metal Complexes

Question 1

Define a complex.

Answer 1

A central metal ion surrounded by ligands.

Question 2

Define a ligand.

Answer 2

Negatively or uncharged molecules with 1+ lone pairs.

Question 3

Define a dative covalent bond.

Answer 3

A covalent bond where both electrons are donated by the same atom.

Question 4

What does monodentate and bidentate mean?

Answer 4

A monodentate ligand donates one lone pair to the central metal ion while bidentate ligands donate two.

Question 5

Define a coordination number.

Answer 5

The number which is determined by the total number of bonds from the ligand to the central metal ion.

Question 6

What are the rules for writing a formula of a complex?

Answer 6

1. The symbol of the metal is first.
2. The negatively charged ligands follow, followed by the neutral ligands.
3. The complex ion is put in brackets.
4. The overall charge is put outside the brackets.

Question 7

What are the orders of naming complexes?

Answer 7

Alphabetical Order, then the metal’s name, then the oxidation states.

Question 8

If the ligand has a negative ion ending in -ide, then the complex ligand name changes the end to an…

Answer 8

O

Question 9

What would a chloride ion’s name be changed to in a metal complex?

Answer 9

Chloro.

Question 10

What is ammonia’s name in a metal complex?

Answer 10

Ammine.

Question 11

What is water’s name in a metal complex?

Answer 11

Aqua.

Question 12

What happens to the end of metals such as iron,copper and cobalt are in a negative complex?

Answer 12

Iron changes to ferrate, copper changes to cuprate and cobalt changes to cobaltate.

Question 13

What is the name of this complex?

K4[Fe(CN)6]

Answer 13

Potassium hexacyanoferrate(II)

Question 14

What is the splitting of the d orbitals and how does it happen?

Answer 14

When ligands approach metal ion, the electrons in the d orbitals of the ion that lie along the axes get repelled by the electrons of the ligands. The d orbitals that lie on the axes now have a higher energy than the d orbitals that lie between the axes.

Question 15

What can change the different in energy between the higher d orbitals and the lower d orbitals?

Answer 15

Whether the ligands approaching the metal ion are weak field or strong field ligands. Otherwise known as its position on the spectrochemical series.

Question 16

How can transition metal compounds absorb light?

Answer 16

Electrons in the lower d orbitals can absorb energy and move to higher energy levels. If the energy absorbed in these transitions is in the visible part of the electromagnetic spectrum, the colour of the transition metal is complementary to the colour absorbed by it.

Question 17

What spectroscopy would be used if a strong field ligand was surrounding the transition metal ion?

Answer 17

Ultraviolet spectroscopy.

Question 18

What spectroscopy would be used if a weak field ligand was surrounding the transition metal ion?

Answer 18

Visible spectroscopy.

Question 19

What type of catalysts are transition metals?

Answer 19

Heterogenous.

Question 20

What does heterogenous and homogenous mean?

Answer 20

A heterogenous catalyst is a catalyst which is in a different physical state than the reactants, a homogenous catalyst is a catalyst which is in the same physical state as the reactants.

Question 21

How do transition metals act as catalysts?

Answer 21

They form weak bonds with the reactants and the unpaired d orbitals which transition metals have allow intermediate complexes to form. These intermediate complexes make the molecule more susceptible to attack by the molecules of the other reactants. An alternative pathway is provided which increases the rate of reaction.

Question 22

What happens with cobalt (II) chloride as a catalyst?

Answer 22

The catalyst is pink at first, but as the reaction goes on more Co3+ ions form causing the colour to go green. Oxygen is given off before Co2+ ions begin to regenerate and the reaction mixture returns to its pink colour.