transition elements-cape chemistry

8/21/2019 Transition Elements-CAPE Chemistry

1/19

Coordination Chemistry

Geometric and optical isomerism

Ainka Brown

[email protected] 1


2/19

Objectives

Examine types of isomerism in coordination

complexes

Geometric

Cis

Trans

Optical

Chiral (mirror images)

2


3/19

Drawing Complexes

3

tetrahedral Square planar Octahedral

Shapes of complexes

Depends on number of donor atoms


4/19

Drawing Complexes

4

Metal at centre.Donor atoms of

ligands bonded to

metal


5/19

Isomerism

Same formula different arrangement of atoms

Geometric and optical isomers

Difference in spatial arrangement of ligands

Geometric isomers

5


6/19

Isomerism

Optical isomers (non-superimposable mirror images)

(bidentate ligands)

6

C

CO O

O

O

C

CO O

O

O

H3N

H3N

C

COO

O

O

C

COO

O

O

NH3

NH3

Mirror plane


7/19

Transition Metals

Chemistry of chromium, iron and copper

Ainka Brown

[email protected] 7


8/19

Chemistry of selected transition metals

Chromium, ,

Objectives

- extraction of the metals from their ores(process and equations)

- Aqueous chemistry

- acidity / basicity of hydrated ions and

hydroxides- redox chemistry

- complexes

8


9/19

Extraction

Chromium

Reduction of chromium(III)oxide by aluminium

Equation(s)?

Description?

Reduction of haematite by carbon monoxide

Equation(s)?

Description?

9


10/19

Extraction

Oxidation of copper(I)sulfide

Equation(s)?

Description?

10


11/19

Hydrated ions - chromium

Chromium

Cr (s) + 2H+(aq) Cr2+(aq) + H2(g)

[Cr(H2O)6]2+

rapidly oxidised to [Cr(H2O)6]3+

blue violet

Violet solution turns green on warming.

(ligand exchange)

[Cr(H2O)6]3+(aq)

Solutions of CrCl3 are acidic11


12/19

Acidity of Cr3+(aq)

[Cr(H2O)6]3+(aq) + 3 OH-(aq) Cr(OH)3(s)

12

OHH

OHH

O

H

H

OH

H

O

H

H

OH

H

Charge density and polarisation

3+

Oxidation state

Zeff


13/19

Amphoteric Cr(OH)3

[Cr(H2O)6]3+ Cr(H2O)3(OH)3 [Cr(H2O)3(OH)4]

-

Other hydroxo species can be formed.

Such as?

13

acid base

base


14/19

Hydrated ions -

Fe(s) + 2H+(aq) [Fe (H2O)6]2+ (depends on the

acid)

[Fe (H2O)6]2+oxidised on standing to [Fe (H2O)6]3+

[Fe(H2O)6]2+(aq) and [Fe(H2O)6]

3+(aq)

Solutions of both FeCl2 and FeCl3 are acidic (similar reasons as for [Cr(H2O)6]

3+(aq))

14


15/19

Basic Fe(OH)2 and Fe(OH)3

Dissolves only in acid

[Fe(H2O)6]2+ Fe(H2O)4(OH)2

[Fe(H2O)6]3+ Fe(H2O)3(OH)3

Fe(OH)3 also formed by air oxidation of Fe(OH)2

15

acid

acid

base

base


16/19

Hydrated ions -

Cu (s) + 2H+(aq) Cu2+(aq) + H2(g) (oxidising acids)

[Cu(H2O)6]2+

Solutions of CuSO4are acidic

(similar reasons as for [Cr(H2O)6]3+(aq))

16


17/19

Basic Cu(OH)2

Dissolves in acid

[Cu(H2O)6]2+ Cu(H2O)4(OH)2

17

acid

base


18/19

Redox chemistry

Chromium

Cr2O72-(aq) + 14H+ + 6e- 2 Cr3+(aq) + 7 H2O (l)

CrO42-(aq) + 4 H2O + 3e

- Cr(OH)3(s) + 5 OH-(aq)

NB: (2 CrO42-

+ 2H+

Cr2O72-

+ H2O)

Iron

Fe2+(aq) Fe3+

(aq) + e-

Copper

2 Cu+ Cu(s) + Cu2+(aq)

18


19/19

Complexes

Iron

Fe3+reacts with thiocyanate anion to give a blood-

red complex

[Fe(H2O)6]3+ (aq) + SCN-(aq) [Fe(SCN)(H2O)5]2+(aq)

Copper

[Cu(H2O)6]2+ + 4 NH3 [Cu(NH3)4]2+

[Cu(H2O)6]2++ 4 HCl-(conc) [CuCl4]

2-

19

transition elements-cape chemistry

Documents