Transition metal complexes
central metal ion surrounded by ligands
ligand
molecule or negative ion which bonds to metal ion by donation
of at least one electron pair into unfilled metal orbitals
common ligands
• water, H20
• ammonia, NH3
• cyanide ion, CN• halides, F-,Cl-,Br- & I• nitrite ion, NO2• hydroxide ion, OH-
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Transition metal complexes 2
ligands
• monodentate e.g. CN-, H2O, NH3
O
O
- O C-C
..
O
..
..
..
• bidentate e.g. ethanedioate (oxalate),
1,2-diaminoethane (ethylenediamine)
H
..
H2N
H
C
C
H
H
..
NH2
• hexadentate e.g. ethylenediaminetetraacetic acid (EDTA)
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(p60)
Transition metal complexes 3
Number of ligands in a complex ion varies depending on the ligand
e.g. [Cu(H2O)6]2+ & [CuCl4]2- both have ligands around the copper(II) ion
Co-ordination number: number of bonds from the ligand to the central
metal ion e.g. copper(II) above has co-ordination numbers of 6 and 4 ,
respectively .
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Shapes of metal complexes
Co-ordination
number
Shape of
complex
X - M - X
2
linear
4
X
4
M
X
square planar
X
X
X
M
tetrahedral
6
X
octahedral
X
X
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M
X
X
X
X
X
X
Formulae of metal complexes
Named according to IUPAC rules
Formula should be enclosed within square brackets
metal symbol written first, then negative ligands followed by
neutral ligands e.g. [CoCl2(NH3)4]
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Naming metal complexes
1.
p60
If the complex is a salt, the name of the positive ion is written before
the name of the negative ion e.g. K3[Fe(CN)6]
2.
The name of the complex part (ion or neutral) consists of 2 parts
written as 1 word.
3.
Ligands are named first, in alphabetical order, and the central metal ion
second.
4.
If the ligand is a negative ion: ‘ide’ is dropped and replaced with ‘o’ e.g.
chloride becomes chloro , cyanide becomes cyano; ‘ate’ and ‘ite’ change
to ‘ato’ or ‘ito’ e.g. oxalate becomes oxalato, nitrite becomes nitrito.
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Naming metal complexes 2
K3[Fe(CN)6]
•
5. Water becomes aqua; ammonia - ammine; carbon monoxide - carbonyl
•
6. The ligand name is preceded by a Greek prefix indicating the number
of each ligand type (di, tri, etc).
•
7. The metal name is followed by the oxidation number,in Roman
numerals, in brackets. The overall charge on the complex part will be
equal to the sum of the oxidation number and the total charge on the
ligands
•
8. If the complex ion is negative, the metal name is followed by ‘ate’ and
then the oxidation number in brackets e.g. cobaltate, chromate. Latin
name is sometimes used e.g. cuprate, ferrate, plumbate, stannate.
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Naming metal complexes 3
1.
K3[Fe(CN)6]
1. potassium hexacyanoferrate(III)
2.
[Cu(NH3)4]Cl2
2. tetraamminecopper(II) chloride
3.
[PtCl2(NH3)2]
3. diamminedichloroplatinum(II)
4.
[Co(H2O)6]Cl2
4. hexaaquacobalt(II) chloride
5.
Na2[PtCl4]
5. sodium tetrachloroplatinate(II)
6.
[CrCl(H2O)5]Cl2
6. pentaaquachlorochromium(III) chloride
7.
[CoCl2(NH3)4]Cl
7. tetraamminedichlorocobalt(III) chloride
8.
[Cu(CN)2(H2O)2]
8. diaquadicyanocopper(II)
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