transition elements-cape chemistry
TRANSCRIPT
-
8/21/2019 Transition Elements-CAPE Chemistry
1/19
Coordination Chemistry
Geometric and optical isomerism
Ainka Brown
-
8/21/2019 Transition Elements-CAPE Chemistry
2/19
Objectives
Examine types of isomerism in coordination
complexes
Geometric
Cis
Trans
Optical
Chiral (mirror images)
2
-
8/21/2019 Transition Elements-CAPE Chemistry
3/19
Drawing Complexes
3
tetrahedral Square planar Octahedral
Shapes of complexes
Depends on number of donor atoms
-
8/21/2019 Transition Elements-CAPE Chemistry
4/19
Drawing Complexes
4
Metal at centre.Donor atoms of
ligands bonded to
metal
-
8/21/2019 Transition Elements-CAPE Chemistry
5/19
Isomerism
Same formula different arrangement of atoms
Geometric and optical isomers
Difference in spatial arrangement of ligands
Geometric isomers
5
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
7/19
Transition Metals
Chemistry of chromium, iron and copper
Ainka Brown
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
9/19
Extraction
Chromium
Reduction of chromium(III)oxide by aluminium
Equation(s)?
Description?
Reduction of haematite by carbon monoxide
Equation(s)?
Description?
9
-
8/21/2019 Transition Elements-CAPE Chemistry
10/19
Extraction
Oxidation of copper(I)sulfide
Equation(s)?
Description?
10
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
17/19
Basic Cu(OH)2
Dissolves in acid
[Cu(H2O)6]2+ Cu(H2O)4(OH)2
17
acid
base
-
8/21/2019 Transition Elements-CAPE Chemistry
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
-
8/21/2019 Transition Elements-CAPE Chemistry
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