Shapes of complexes

Question 1

What shape does a complex with coord number of 6 form?

Answer 1

Octahedral

Question 2

Bond angle of octahedral

Answer 2

90 degrees

Question 3

Why do complexes with coord number of 6 have an octahedral shape?

Answer 3

Form 6 dative covalent bonds around a central transition metal ion and has no lone pairs

Question 4

Examples of small ligands

Answer 4

OH-
H2O
NH3

Question 5

Cis octahedral complex

Answer 5

Same ligand is 90 degrees apart

Question 6

Trans octahedral complex

Answer 6

Same ligand is 180 degrees from central transition metal ion

Question 7

Can octahedral complexes show cis trans geometric isomerism?

Answer 7

Yes

Question 8

Bond angle of tetrahedral

Answer 8

109.5 degrees

Question 9

What shape is a complex bonded to large ligands?

Answer 9

Tends to be tetrahedral

Question 10

Examples of a large ligand

Answer 10

Cl-

Question 11

Why is a tetrahedral shape complex formed from large ligands?

Answer 11

Because large ionic radii of Cl- means its not possible for more than 4 to form dative bonds to central transition metal ion

Question 12

Square planar

Answer 12

4 ligands around central transition metal ion
in a plane

Question 13

Bond angle in square planar

Answer 13

90 degrees

Question 14

Examples of square planar complexes

Answer 14

Cisplatin
Transplatin

Question 15

Cis platin structure

Answer 15

Central ion= Pt
2 Cl ligands
2 NH3 ligands are both 90 degrees apart

Question 16

Trans platin structure

Answer 16

Central ion = Pt
2 Cl ligands
2 NH3 ligands are both 180 degrees apart

Question 17

Linear complex

Answer 17

Contains 2 ligands bonded in a line

Question 18

Linear complex bond angle

Answer 18

180 degrees

Question 19

Example of linear shaped complex

Answer 19

Tollens reagent
[Ag(NH3)2]+

Question 20

Why can a monodentate ligand like H2O only form 1 dative bond if there are multiple lone pairs?

Answer 20

When 1 lone pair forms dative bond, the other lone pair faces away and since they are on the same atom, geometrically impossible

Question 21

Monodentate ligand

Answer 21

An ion or molecule that is able to form 1 dative covalent bond to a central transition metal ion in a complex

Question 22

Bidentate ligand

Answer 22

a species that is able to form two co-ordinate bonds to a transition metal ion. (can also be called a multidentate ligand)

Question 23

Examples of bidentate ligand

Answer 23

En = NH2CH2CH2NH2
Ethanedioate = -OO-C-C-OO-

Question 24

Structure of en ligand

Answer 24

NH2CH2CH2NH2

Question 25

Where does the 2 dative bond form on the en ligand

Answer 25

Lone pair of electrons on both nitrogen So forms 2 dative bonds to central atom per ligand

Question 26

Where does the 2 dative bonds form on ethanedioate ligand?

Answer 26

The lone pair of electrons on the O- atom NOT THE O=C

Question 27

Bidentate ligands form complexes of what shape?

Answer 27

Octahedral

Question 28

Example of multidentate ligand?

Answer 28

EDTA 4-

Question 29

How many dative bonds form per EDTA 4- anion?

Answer 29

6

Question 30

Octahedral molecule ratio of transition metal to EDTA 4-

Answer 30

1:1

Question 31

Denticity of a ligand

Answer 31

How many co-ordinate bonds it is able to form with a transition metal ion Eg is it monodentate, bidentate?

Question 32

Chelate effect

Answer 32

When multiple ligands of low denticity exchange for a lower number of ligands with higher denticity

Question 33

Examples of chelate effect

Answer 33

When 6 monodentate ligands are exchanged for: -3 bidentate ligands -1 EDTA 4- ligand

Question 34

Why does chelate effect occur in terms of entropy?

Answer 34

Favourable because of the increase in number of particles so increase in entropy Means Gibbs value is negative