Transcript Complexes

Complexes
Complexes
Compounds in which a metal atom or ion is surrounded by a
number of oppositely charged ions or by neutral molecules.
All possessing lone pairs of electrons which are available for
donation to vacant orbitals of the metal atom or ion.
Structure
1.
[Hexaammineplatinum(IV)] chloride
[Pt(NH3)6]Cl4
central ion
coordination number
ligand
complex cation
2.
Potassium hexachloroplatinate(IV)
K2[PtCl6]
central ion
coordination number
ligand
complex anion
3.
Iron(O)pentacarbonyl
[Fe(CO)5]
central atom
coordination number
ligand
complex molecule
Central ions, atoms:
Transition metals
Alkaline earth metals
Alkaline metals
Coordination numbers:
Number of ligands in the first
coordination sphere
Complexes with various coordination
numbers
Coordination
Complex
number
2
3
4
5
[Ag(NH3)2]+, [CuCl2][HgI3][Zn(NH3)4]2+, [Ni(CN)4]2[Ni(CN)5]3-, Fe(CO)5
6
7
8
[Cr(H2O)6]3+, [Fe(CN)6]3[ZrF7]3[Mo(CN)8]4-
Geometry:
L
L
M
L
M
L
L
L
linear (2)
tetrahedral (4)
L
L
L
L
L
M
M
L
L
square planar (4)
L
L
L
octahedral (6)
Monodentate Ligands
Cations:
H2N-NH3+
Anions:
F-, Cl-, OH-, CN-, NO3-, NO2Neutral molecules:
H2O, NH3, CO
Cl
O H
-
C
N
H
Water
C
Ammonia
O
Carbon monoxide
N
Chloride
ion
C
S -
Thiocyanate
ion
Cyanide
ion
O
H
-
Hydroxide
ion
-
Polydentate Ligands
H 2N
NH2
H 2N
H 2C
H 2C C H 2
O
-
C
O
C
O
O
Oxalate ion
O
CH2
CH2
C
O
Glycinate ion (gly-)
N CH2
-
O
C
O
O
O
C
O
Ethylenediamine
(en)
-
-
CH2
C
O
CH2 N
CH2
C
O
O
Ethylenediaminetetraacetate ion (EDTA4-)
-
-
-
Chelates
Bi- or polydentate ligands
Men+n+
Me
n+n+
Me
Me
Nomenclature: IUPAC
1. Cation preceeds anions
2. Ligands preceed central ions or atoms
3. Anion ligands: -o ending (hydroxo, chloro,
cyano…)
4. Cations, neutral molecules: unchanged
Exception(!): aqua, ammine, carbonyl, nitrosyl
5. Complex anions: -ate ending
6. Oxidation state: Roman numbers
Dissociation of complexes
Conductance*
Number
of ions
Number
of
chloride
ions
[Pt(NH3)6]Cl4
523
5
4
[Pt(NH3)5Cl]Cl3
404
4
3
[Pt(NH3)4Cl2]Cl2
228
3
2
[Pt(NH3)3Cl3]Cl
97
2
1
[Pt(NH3)2Cl4]
0
0
0
K[Pt(NH3)Cl5]
108
2
0
K2[PtCl6]
256
3
0
Formula
*Molar conductance:
cm2/·mól, 0,001M, 25°C
Stability constant, formation
Properties of metal complex differ from metal ion!
1.
2.
3.
4.
Colour changing
Solubility
Ligand reactions
Number of particles, dissociation
Formation constant: Kstab (stability constant)
Pl.: Ag+ + 2NH3
K=
[Ag(NH3)2]+
[Ag(NH3)2]+
[Ag+][NH3]2
Dissociation constant:
= 1,7·107
1
Kd =
[Kstab]
Izomerism
Isomers
Constitutional isomers
Linkage isomers
Ionization isomers
Stereoisomers
Diastereoisomers
Enantiomers
CrCl3·6H2O
[Cr(H2O)6]Cl3
[Cr(H2O)4Cl2]Cl·2H2O
[Cr(H2O)5Cl]Cl2·H2O
cis
trans
NH3
NH3
NH3
Cl
Co
Cl

Co
NH3
NH3
NH3
Cl

Cl
NH3
NH3
[dichloro-tetraammine-cobalt(III)] ion
Cl
Cl
Cl
en
Cl
Co
Co
en
en
[dichloro-bis(etylenediammine)cobalt(III)] ion
en = etylenediammine
en
Bonding in complexes:
•Valence Bond Theory
•Crystal Field Theory