Download 15.2 COMPLEX FORMATION And THE SHAPE OF COMPLEX IONS

COMPLEX FORMATION And THE
SHAPE OF COMPLEX IONS
L.O.:
 Recall definition of ‘ligand’, ‘co-ordinative
bond’, ‘co-ordination number’.
 Identify unidentate, bidentate and
multidentate ligands.
 Explain the effect of the size of ligand on
the shape of the complex ion.
2+
H2.O.
H2O:
Fe
H2O:
:OH2
:OH2
..
H2O
A complex ion is formed
when a transition metal
ion is surrounded by ions
or other molecules (called
ligands), which are bonded
to it by co-ordinative
bonds.
The number of co-ordinative bond that
surround the metal ions called co-ordination
number.
COMPLEX IONS - LIGANDS
Ligands
atoms, or ions, which possess lone pairs of electrons
form co-ordinate bonds to the central ion
donate a lone pair into vacant orbitals on the central species
Ligand
Formula
chloride
Cl¯
cyanide
NC¯
hydroxide HO¯
oxide
O2water
H2O
ammonia
NH3
Name of ligand
chloro
cyano
hydroxo
oxo
aqua
ammine
CO-ORDINATION NUMBER & SHAPE
the shape of a complex is governed by the number of ligands around the central ion
the co-ordination number gives the number of ligands around the central ion
a change of ligand can affect the co-ordination number
Co-ordination No. Shape
Example(s)
6
Octahedral
4
Tetrahedral
2
[Cu(H2O)6]2+
[CuCl4]2-
Square planar
Pt(NH3)2Cl2
Linear
[Ag(NH3)2]+
Multidentate ligands: have more than one
lone pair which can bond to a transition
metal.
Ligands which form only one co-ordinative
bond per ligand and are said to be
unidentate.
Ligands which donate 2 lone pairs per ligand
and are said to be bidentate.
Multidentate ligands have more than one
lone pair which they can bond to a transition
metal.
edta
COMPLEX IONS - LIGANDS
some ligands attach themselves using two or more lone pairs
classified by the number of lone pairs they use
multidentate and bidentate ligands lead to more stable complexes
Multidentate
form several co-ordinate bonds
HAEM
A complex containing iron(II) which is
responsible for the red colour in blood
and for the transport of oxygen by red
blood cells.
Co-ordination of CO molecules interferes
with the process
Cis-platin
Cl
Pt
Cl
Anticancer drug.
NH3
NH3
5.4 EXERCISE 2 – Complex ions