1. Unless otherwise stated, all images in this file have been reproduced from:
Blackman, Bottle, Schmid, Mocerino and Wille,      Chemistry, 2007 (John Wiley)      ISBN:

2. CHEM1002 [Part 2] Dr Michela Simone Lecturer
BSc (I Hons), MSc, D.Phil. (Oxon), MRSC, MRACI
Weeks 8 – 13
Office Hours: Monday 3-5, Friday 4-5
Room: 412A (or 416)
Phone:
It is a good idea if all lecturers can make an appearance for the first lecture.
Remind students we are IT for the rest of the semester.
DEMOS for this lecture:
EXP 2.3: “Charles law (2.3),
EXP 2.1 “CO2 density (2.1)

3. Summary of Last Lecture
Solubility Equilibria II
The solubility of a salt MmXn is reduced by the addition or presence in solution of either Mn+ or Xm- from another source – the common ion effect
The solubility of hydroxides is very sensitive to pH since this controls [OH-(aq)]
The solubility of a salt in the presence of a common ion can be calculated from the solubility product as this gives the maximum concentrations of the ions that are allowed

4. Complexes I Lecture 12 Hydrolysis of Metal Ions Metal Complexes
Ligands
Blackman Chapter 13, Sections
Lecture 13
Isomerism
Stability

5. Hydrolysis of Metal Ions+
M(H2O)42+(aq)
M2+
H2O(l)
adduct
Metal cations act as Lewis acids (electron pair acceptor)
Water is the Lewis base (electron pair donor)

6. Acidity of Aqueous Transition Metal Ions
[Fe (OH2)5(OH)] H+
[Fe(OH2)6]3+

7. Metal Ion Hydrolysis Free Ion Hydrated Ion Ka Fe3+ Fe(H2O)63+(aq)
6 x 10-3
Cr3+
Cr(H2O)63+(aq)
1 x 10-4
Al3+
Al(H2O)63+(aq)
1 x 10-5
Be2+
Be(H2O)42+(aq)
4 x 10-6
Cu2+
Cu(H2O)62+(aq)
3 x 10-8
Pb2+
Pb(H2O)62+(aq)
Zn2+
Zn(H2O)62+(aq)
1 x 10-9
Co2+
Co(H2O)62+(aq)
2 x 10-10
Ni2+
Ni(H2O)62+(aq)
1 x 10-10
ACID STRENGTH
The higher the metal charge, the greater the hydrolysis
The smaller the metal ion, the greater the hydrolysis

8. The Coordination Bond L Mn+ L
A ligand donates an electron pair to the metal ion to form a coordinate or dative bond.
All ligands have at least one lone pair
some ligands have more than one lone pair and can bond to two or more metal ions
Usually more than one ligand binds to the metal ion
commonly 4 or 6 ligands coordinate to a metal

9. Metal Complexes A coordination compound:
a complex ion (the metal and its ligands)
counter ions to balance its charge
The metal ion has a positive charge (Co3+, Fe2+, Cu2+ etc)
The ligands can be:
neutral (NH3, OH2, pyridine, amines etc), giving rise to positively charged complexes (e.g. [Co(NH3)6]3+)
negatively charged (Cl-, OH-, CN- etc), giving rise to negatively charged complexes (e.g. [Co(CN)6]3-)
a mixture of these, giving rise to positive, negative or neutral complexes (e.g. [Co(NH3)3(CN)3]

10. [Co(NH3)6]Cl3 [Co(NH3)6]3+(aq) + 3Cl-(aq)
Metal Complexes
[Co(NH3)6]Cl3
Square brackets indicate the complex ion:
[Co(NH3)]3+
Co3+ with six neutral NH3 ligands
Three Cl- counter ions to balance the charge
When dissolved in water, the complex ions and counter ions are separate
[Co(NH3)6]Cl [Co(NH3)6]3+(aq) + 3Cl-(aq)

11. Coordination Number The number of ligands bonded to the metal ion
varies from depending on the metal and ligand sizes and charges
4 and 6 are the most common
Typical coordination number for some metal ions.
M+ CN M2+ CN M3+ CN
Cu+ 2,4 Mn2+ 4,6 Sc Ag+ 2 Fe2+ 6 Cr Au+ 2,4 Co2+ 4,6 Co Ni2+ 4,6 Au Cu2+ 4, Zn2+ 4,6

12. Complex Geometry CN Geometry Examples 2 linear [Ag(NH3)2]+ [AuCl2]- 4
square planar
[Pd(NH3)4]2+
[PtCl4]2-
tetrahedral
[Zn(NH3)4]2+
[CuCl4]2- 6
octahedral
[Co(NH3)6]3+
[FeCl6]3-

13. Chelate Ligands Unidentate or monodentate) ligand – forms one bond
Bidentate ligand – can form two bonds
Polydentate ligand – can form > two bonds
tridentate
tetradentate
pentadentate
hexadentate
etc ...
CHELATE
LIGANDS
Chelate effect: complexes with chelate ligands are usually more stable than those with monodentate ligands of the same type:

14. Some Chelate Ligands
Bidendate
ethane-1,2-diamine (en)

15. Some Chelate Ligands Hexadendate
ethane-1,2-diaminetetraacetic acid (H4EDTA)
EDTA4-
[Co(EDTA)]-
EDTA is used to treat severe lead poisoning ...and to soften water in shampoo and soaps

16. Summary: Complexes I Complete the worksheet
Learning Outcomes - you should now be able to:
Complete the worksheet
Explain why solutions of metal ions are acidic
Identify the complex ion and ligands in a coordination compound
Draw representations of octahedral, tetrahedral and square planar complexes using tapered bonds
Answer review problems in Blackman
Next lecture:
Isomerism and stability of complexes

17. Practice Examples
What are the possible geometries of a metal complex complex with a coordination number of 4?
square planar or tetrahedral or octahedral
square planar or tetrahedral
octahedral only
tetrahedral only
square planar only
The nickel(II) ion exists as the [Ni(OH2)6]2+ complex ion in aqueous solution. Define the term complex.
Why is such a solution acidic?
Write a balanced equation for the corresponding reaction.

18. Naming Metal Complexes: (i) Ligands
The normal chemical name is used unless the ligand is negatively charged in which cases “o” is used as the suffix
Neutral
aqua
H2O
ammine
NH3
amine
CH3NH2 etc
Special Cases
Anionic
fluorido F-
chlorido
Cl-
bromido
Br-
iodido I-
cyanido
CN-
hydroxido
OH-

19. Naming Metal Complexes: (i) Ligands
The number of ligands of any one type is indicated with the appropriate Greek prefix
monodentate: di, tri, tetra, penta, hexa, etc
e.g. dichlorido, tetraaqua, hexaamine
polydentate: bis, tris, tetrakis etc
If there is more than one ligand type
Listed in alphabetical order with no space between them!
Prefixes do not affect the order
diamminedichloridodifluorido A < C < F
triamminedichloridofluorido A < C < F

20. Naming Metal Complexes: (ii) Metal
If the complex is neutral or positively charged the normal metal name is used
If the complex is negatively charged, ‘ate’ is added to the metal name
Co: cobaltate
Zn: zincate
Exceptions (historic):
Metal
Name in anion
not:
iron
ferrate
ironate
copper
cuprate
copperate
lead
plumbate
leadate

21. Naming Metal Complexes: (iii) Metal
Metal is named after ligands with no space between them!
The oxidation state of the metal is indicated by Roman numerals
Fe3+ is given as iron(III)
Mn7+ is given as manganese(VII)

22. Naming Metal Complexes
Counter ions are named as separate words and are not numbered
cations before the complex ion
K3[Co(CN)6]
potassium hexacyandidocobaltate(III)
anions after the complex ion
[Co(NH3)4Cl2]Cl
tetraamminedichloridocobalt(III) chloride

23. Naming Metal Complexes
Indicating the presence of solvent molecules
Water of crystallisation (hydration) is indicated separately at the end of the name
[Co(NH3)4Cl2]Cl·2H2O tetraamminedichlorocobalt(III) chloride-2-water