Present a short review about Crystal field theory and how we can use the results of it to explain various physico-chemical properties of transition metal complexes.

1. Properties of
Coordination Compounds
Part 1 (1/3)
Applications of Crystal Field Theory
Dr.Christoph Sontag
University of Phayao 2015

3. Coordination Compounds

4. Factors determining the type of bonds
(1) Oxidation number of the metal
ox.no. 0 indicates a
covalent M-L bond
(2) Coordination number
-> Coordination compounds show the
appropriate number of ligands, in contrast to
ionic compounds
Cu(SO4) as salt and as
coordination compound:

5. Common Coordination numbers
early middle Co-Ni late
4 6 4 2

6. Which category of compound ?
Fe(CO)5 ox.no. cat:
FeCl3 ox.no. cat:
(in water: pH 3)
K3Fe(CN)6 ox.no. cat:
CuSO4 ox.no. cat:
Cu(CN) 4
(2-) ox.no. cat:
Cu(OAc)2
(2-) ox.no. cat:

7. Example
A) [Cr(NH3)3Cl3]
B) [Cr(NH3)6]Cl3
C) Na3[Cr(CN)6]
D) Na3[CrCl6]
Which of these compounds will form
a precipitation with AgNO3 ?

8. Review: CFT
Applications of Crystal Field Theory

9. Crystal Field Theory Review
http://wwwchem.uwimona.edu.jm/courses/CFT.html

10. http://www.youtube.com/watch?v=LydEaN8-WJ8

11. Spectrochemical series

12. Conclusions from CFT

13. Extension: LFT

14. pi-donor ligands => low splitting

15. pi-acceptor ligands => high splitting

16. Symmetry Symbols
http://www.webqc.org/symmetrypointgroup-td.html

17. Which symmetry do the 5 d-orbitals in a tetrahedron have ?

18. Conclusions from LFT

19. (1) Find the configuration (as tx
2gey
g / ext2
y), the number of
unpaired electrons and the LFSE (in terms of ∆o / ∆t and P)
(2) Which of the following complexes has higher LFSE:
(h) [MnF6]3- i) [NiBr4]2- j) [Fe(CN)6]4-

20. Applications of CFT
(1) Electronic spectra
(2) Hydration energies
(3) Lattice energies
(4) Ionic radii
(5) Spinel types

21. (1) Electronic Spectra (example)
Each peak in the spectrum (λ <-> ν ) corresponds to a change
in the electronic state (Shriver/Atkins p.576)

22. Find ∆o from Tanabe-Sugano diagrams
∆/B
E/B
V(H2O)6
2+ shows 2 peaks at
17200 and 25600 cm-1
(1) Get E-ratio: E2/E1 = 1.49
(2) Find by trial and error this ratio
in the diagram => ∆/B
we find here a value of 40/27 = 29
(3) From this we find B:
E2 = 25600 = 40 *B
E1 = 17200 = 27 *B => B = 640 cm-1
(4) When B is know, then
∆o = 29 * 640 cm-1 = 18600 cm-1

23. http://www.chem.uky.edu/courses/che610/JPS_Spring_2007/
PS2_2007key.pdf
Self-study:

24. Energy ratios:
E2/E1 = 1.8
E3/E1 = 3.05
E3/E1 = 1.68
Now we move on the x-axis until
we find this ratio in the y values
again (approximately !)
=> ∆/B = 10
from that we get B:
E3/B = 29 (graph) => B = 896 cm-1
=> ∆o = 10 * 896 cm-1 = 8960 cm-1
(more exact: take the average for all 3 found B values)

25. -> B= 25700 / 41 = 628 cm-1 -> v3 = 59 * B = 37000 cm-1

26. (2) Hydration energies

27. Example
Find the solution enthalpy for CaCl2:
-> we can look up the HYDRATION energies for both ions:
-> the LATTICE energy for CaCl2 is +2258 kJ mol-1
http://www.chemguide.co.uk/physical/energetics/solution.html

28. Lattice Energy
Hydration
Energy

29. http://www.youtube.com/watch?v=awD1qa7TF4A

30. Example: Ti(H2O)6
2+
What is the additional hydration energy for 1 mol due to
the 2 d electrons? (Δo = 8000 cm-1)
(1 cm-1 = 0.012 kJ/mol)

31. (3) Lattice energies
Lattice Energy is used to explain the stability of ionic
solids
= the energy required to break apart an ionic solid and
convert its component atoms into gaseous ions
-> cannot be measured directly
Born-Haber cycle

32. Experimental data vs. calculated for MCl2 high-spin
compounds according to the Born-Haber Cycle

33. Example
What is the additional Lattice Energy for VCl2 due to
the d electrons in Vanadium ion ?
(Δo = 5500 cm-1)
(1 cm-1 = 0.012 kJ/mol)

34. (4) Ionic Radii M(2+) --- O

35. M2+ ions in water are in a weak field => they are all high-spin
Then we get 2 minima in the radii at V2+ with 3 electrons in the t2g
levels and Ni2+ with 6 electrons in t2g
For low-spin there is only one minima at Fe2+ with 6 electrons in t2g

36. Example
Estimate which M-O distance is the shortest:
a) Fe2O3 (low spin)
b) FeO (low spin)
c) Fe(H2O)6
3+ (high spin)

37. (5) Spinels (gemstones)
Spinels = crystals formed by mixed oxides,
originally used for MgAl2O4
In a closed packed solid, there are tetrahedral and
octahedral “holes” filled with a metal ion.
“ cubic closed packing”
(https://www.youtube.com/watch?v=U_n7DyCqv6U)

38. Example
What is the oxidation number of Fe in Fe3O4 ?

39. “normal”: A in Td , B in Oh holes
Fe3O4 is a spinel type : Fe2+ (Fe3+ )2 O4
“inverse”: A in Oh,
1/2B in Td and 1/2B in Oh
(neglectpairingenergyP)
http://www.everyscience.com/Chemistry/Inorganic/
Crystal_and_Ligand_Field_Theories/e.1016.php
“Magnetite”

40. If M3+ has a higher CFSE than M2+ in an octahedral
field, these ions will prefer octahedral holes and
forms a “normal” spinel.
Predict the structure for Mn3O4

41. Applications for Spinels
Spinel Ferrites M2+ Fe3+
2 O4
Fe-O framework
Spinel Aluminates M2+ Al3+
2 O4
Al-O framework

42. https://www.youtube.com/watch?v=U_n7DyCqv6U

45. Visualization of molecules and orbitals
www.chemtube3d.com

46. 3D structures of crystals
Fe(2+)
Fe(3+)