Properties of coordination complexes Complete
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The document discusses the properties of coordination compounds, focusing on various examples and their behavior in precipitation reactions and crystal field theory applications. It covers topics such as electronic spectra, ligand field stabilization energy, and the stability of coordination compounds, including the impact of different ligands on stability and properties. Additionally, it delves into magnetism and the concepts underlying paramagnetism and spin crossover in coordination compounds.
![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 ?](https://image.slidesharecdn.com/properties-of-coordination-complexes-2014-160213161422/85/Properties-of-coordination-complexes-Complete-3-320.jpg)
![(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-](https://image.slidesharecdn.com/properties-of-coordination-complexes-2014-160213161422/85/Properties-of-coordination-complexes-Complete-15-320.jpg)
![Deviations from spin-only formula
Example:
[Fe(CN)6]3- has μ = 2.3μB
which is between low- and high-spin calculated
(check this out)](https://image.slidesharecdn.com/properties-of-coordination-complexes-2014-160213161422/85/Properties-of-coordination-complexes-Complete-57-320.jpg)
![Example 1
Assume that in the reaction of Cu2+ with ammonia,
the only complex ion to form is the tetra-ammine
species, [Cu(NH3)4]2+.
Given a solution where the initial [Cu2+] is 0.10M,
and the initial [NH3] is 1.0M and that β4 = 2.1 x 1013,
calculate the equilibrium concentration of the
Cu2+ ion.
http://wwwchem.uwimona.edu.jm/courses/IC10K1.html](https://image.slidesharecdn.com/properties-of-coordination-complexes-2014-160213161422/85/Properties-of-coordination-complexes-Complete-75-320.jpg)
Properties of coordination complexes Complete
- 3. 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 ?
- 4. Review: CFT Applications of Crystal Field Theory
- 5. Crystal Field Theory Review http://wwwchem.uwimona.edu.jm/courses/CFT.html
- 10. pi-donor ligands => low splitting
- 11. pi-acceptor ligands => high splitting
- 13. Which symmetry do the 5 d-orbitals in a tetrahedron have ?
- 15. (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-
- 16. Applications of CFT (1) Electronic spectra (2) Hydration energies (3) Lattice energies (4) Ionic radii (5) Spinel types
- 17. (1) Electronic Spectra (example) Each peak in the spectrum (λ <-> ν ) corresponds to a change in the electronic state (Shriver/Atkins p.576)
- 18. 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
- 19. http://www.chem.uky.edu/courses/che610/JPS_Spring_2007/ PS2_2007key.pdf Self-study:
- 20. 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)
- 23. (3) Lattice energies Experimental data vs. calculated for MCl2 high-spin compounds according to the Born-Haber Cycle
- 24. (4) Ionic Radii M(2+) --- O
- 25. 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
- 26. (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)
- 27. Example What is the oxidation number of Fe in Fe3O4 ?
- 28. “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”
- 29. 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
- 30. Applications for Spinels Spinel Ferrites M2+ Fe3+ 2 O4 Fe-O framework Spinel Aluminates M2+ Al3+ 2 O4 Al-O framework
- 34. Visualization of molecules and orbitals www.chemtube3d.com
- 35. 3D structures of crystals Fe(2+) Fe(3+)
- 39. Ferro-, Ferri-, Antiferro-, Para- Magnetism http://en.wikipedia.org/wiki/Curie_temperature
- 40. Para-magnetism Atoms that have unpaired electrons (also metals) and therefore a total electron-spin S. These individual magnetic moments can be oriented by an outer magnetic field to line up. Paramagnetic substances are not magnetic by themselves but can become magnetic when an outer field is applied. Every ferromagnetic material has a Curie-Temperature Tc where it loses its permanent magnets and becomes para-magnetic.
- 41. Curies Law Describes the “magnetic susceptibility” of a material dependent on the outer field B and Temperature T => High magnetization M: (a) High external field B (b) Low temperature Or: ‘chi” = magn. susceptibility
- 42. Curies Temperature Tc Heating up a permanent magnet brings the spins to become randomly oriented (at temperature Tc) -> the material loses its magnetism but can still become magnetic again in an external field
- 45. Magnetic Properties Paramagnetism arises from unpaired electrons. Each electron has a magnetic moment with one component associated with the spin angular momentum of the electron and (except when the quantum number l ¼0) a second component associated with the orbital angular momentum. (p.579)
- 46. Where does magnetism come from ?
- 47. Effect of unpaired electrons http://www.youtube.com/watch?v=qfooM_Gl69k
- 48. Gouy Balance
- 51. Examples
- 52. Conclusions from magn. susceptibility
- 54. Spin Cross Over SCO Some complexes can change from low-spin to high- spin at higher temperatures: => low magnetic moment -> high m.m. => M-L bonds short -> longer (why ?) This can happen quickly in a small T-range http://www.youtube.com/watch?v=e9SMMA9Xe9c
- 55. SCO applications
- 56. Spin and orbital contributions to the magnetic moment If S-L coupling is weak
- 57. Deviations from spin-only formula Example: [Fe(CN)6]3- has μ = 2.3μB which is between low- and high-spin calculated (check this out)
- 58. Russell-Saunders Coupling (L-S Coupling) Important esp. for second and third row metal compounds There we cannot use the simple spin-only formula anymore https://www.youtube.com/watch?v=1W7dou4kAU8
- 59. Spin-orbitcoupling Is higher than spin-only – typical for d-complexes with more than half-filled d-shell
- 60. Info to solve problems:
- 63. Electronic states review Alternative to state the electron configuration of an ion as 4s2 3d6, we can express this configuration as “microstates”: Ti(3+): 4s0 3d1 Microstates: S = ½ L = 2 (“d”) => J = 5/2, 3/2 ( L+S),(L+S-1),…(L-S) Ground State with lowest J: 2D3/2
- 66. Examples
- 68. Attkins p.505
- 72. Equilibrium constant K and β http://www.youtube.com/watch?v=LydEaN8-WJ8
- 73. Entropy effect
- 75. Example 1 Assume that in the reaction of Cu2+ with ammonia, the only complex ion to form is the tetra-ammine species, [Cu(NH3)4]2+. Given a solution where the initial [Cu2+] is 0.10M, and the initial [NH3] is 1.0M and that β4 = 2.1 x 1013, calculate the equilibrium concentration of the Cu2+ ion. http://wwwchem.uwimona.edu.jm/courses/IC10K1.html
- 78. Examples Calculate the equilibrium concentration of the Fe3+ ion in a solution that is initially 0.10 M Fe3+ and 1.0 M SCN-, given that β2 for Fe(SCN)2 + = 2.3 x 103
- 79. (1) Irving-Williams series M-L bonds become more covalent
- 80. Hydration energy gets higher if LFSE is more negative ! (2) Ligand Field Stabilization Energy
- 81. (3) Jahn-Teller Effect Estimate which d-orbital occupation(s) can cause a JT effect ….. (distinguish between high- and low-spin)
- 83. Example Cr(II)(H2O)6 Why is a distortion to D4h preferred over regular Oh ?
- 84. Solution: estimate the LFSE for both symmetries For both symmetries, the 3 electrons in the lower levels have LFSE = 3 (-3/5 ∆o) But the one electron in the upper level is lower in energy for D4h therefore the total LFSE is more negative (more stable)
- 86. “Hard acids” Small metal ions with high charge (Fe 3+, Co 3+, Ni 3+) “Soft acids” Bigger metal ions with low charge (Cu 2+, Ag +, Au +, Pt 2+) “Hard bases” ligands with low polarization (F -, OH -, Cl -, NH3) “Soft bases” ligands with high electron density (I -, SCN -, CN -, CO, PR3)
- 89. “basicity” high electron density
- 91. Estimate basicity of molecules Order these ligands from lowest to highest basicity NH3 PH3 P(CH3)3 SR2 F- Br- OH- CN- Main effect is the electron density ! Determined by: electronegativity of atom with lone pair and/or electron-pull or donate effect of neighbor atoms
- 94. Example the driving force is the increase in entropy
- 96. Conclusion Complexes formed by multidentate ligands are much more stable than those formed by “normal” ligands !
- 97. (8) Bulk and Size of Ligands