Optical Isomers: The mirror image of a species
cannot be superimposed on the original structure.
2641
Optical Isomers: The mirror image of a species
cannot be superimposed on the original structure.
Review of some terminology
2642
Optical Isomers: The mirror image of a species
cannot be superimposed on the original structure.
Review of some terminology
Chiral: Molecules or ions that have nonsuperimposable mirror images.
2643
Optical Isomers: The mirror image of a species
cannot be superimposed on the original structure.
Review of some terminology
Chiral: Molecules or ions that have nonsuperimposable mirror images.
Dextrorotatory: The optical isomer that rotates the
plane of polarization to the right (as viewed
towards the incoming beam). The isomer is labeled
with a (+) and sometimes a d.
2644
Levorotatory: The optical isomer that rotates the
plane of polarization to the left (as viewed towards
the incoming beam). The isomer is labeled with a (-)
and sometimes an l.
2645
Levorotatory: The optical isomer that rotates the
plane of polarization to the left (as viewed towards
the incoming beam). The isomer is labeled with a (-)
and sometimes an l.
Optically active: A compound with the ability to
rotate the plane of polarized light.
2646
Levorotatory: The optical isomer that rotates the
plane of polarization to the left (as viewed towards
the incoming beam). The isomer is labeled with a (-)
and sometimes an l.
Optically active: A compound with the ability to
rotate the plane of polarized light.
Racemic mixture: A mixture of equal amounts of an
optically active compound and its mirror image.
2647
Levorotatory: The optical isomer that rotates the
plane of polarization to the left (as viewed towards
the incoming beam). The isomer is labeled with a (-)
and sometimes an l.
Optically active: A compound with the ability to
rotate the plane of polarized light.
Racemic mixture: A mixture of equal amounts of an
optically active compound and its mirror image. A
racemic mixture will not rotate the plane of
polarized light because the rotatory effects of the
two isomers cancel each other.
2648
F
I
I
Zn
Zn
Br
Cl Cl
Br
F
mirror plane
[Zn(BrClFI)]2- ion
2649
F
I
I
Zn
Zn
Br
Cl Cl
Br
F
mirror plane
[Zn(BrClFI)]2- ion
Cannot superimpose these two species;
bromochlorofluoroiodozincate ion is chiral.
2650
2651
cis-isomer: Structure I and the mirror image II are
optical isomers.
trans-isomer: There are no optical isomers for this
complex ion.
2652
Some Applications of Coordination
Compounds
2653
Some Applications of Coordination
Compounds
Water treatment: Ca2+ and Mg2+ can be removed as
a water soluble EDTA complex. P3O105- is also used
as a chelating agent for these ions.
2654
Some Applications of Coordination
Compounds
Water treatment: Ca2+ and Mg2+ can be removed as
a water soluble EDTA complex. P3O105- is also used
as a chelating agent for these ions.
2655
Extraction of Metals: Gold and silver can be
extracted as cyanide complexes with the ligand
CN-. Ni can be purified using Ni(CO)4 where CO
is the ligand.
2656
Extraction of Metals: Gold and silver can be
extracted as cyanide complexes with the ligand
CN-. Ni can be purified using Ni(CO)4 where CO
is the ligand.
Dyes: There are several dyes that are based on
coordination compounds.
2657
Extraction of Metals: Gold and silver can be
extracted as cyanide complexes with the ligand
CN-. Ni can be purified using Ni(CO)4 where CO
is the ligand.
Dyes: There are several dyes that are based on
coordination compounds.
Chemical analysis: There are a number of
coordination compounds that are routinely used
in chemical analysis.
2658
CH3
C N
OH
C N
OH
CH3
Dimethylglyoxime forms a red complex with Ni2+
which is used both as a test for Ni2+ and in
gravimetric analysis for the determination of the
amount of Ni in samples.
2659
Bonding in Coordination Compounds
Crystal Field Theory
2660
Bonding in Coordination Compounds
Crystal Field Theory
Crystal field theory is an ionic model of bonding
used for coordination compounds.
2661
Bonding in Coordination Compounds
Crystal Field Theory
Crystal field theory is an ionic model of bonding
used for coordination compounds. This theory
considers the bonding in complexes purely in terms
of electrostatic interactions between the metal ion
and the ligands.
2662
Bonding in Coordination Compounds
Crystal Field Theory
Crystal field theory is an ionic model of bonding
used for coordination compounds. This theory
considers the bonding in complexes purely in terms
of electrostatic interactions between the metal ion
and the ligands.
All d-orbitals have the same energy in the absence
of an external disturbance.
2663
The case of octahedral geometry
2664
If we place a metal ion in the center of an
octahedron surrounded by six negative charges –
two types of electrostatic interactions come into
play:
2665
If we place a metal ion in the center of an
octahedron surrounded by six negative charges –
two types of electrostatic interactions come into
play:
1. There is the attraction between the negatively
charged ligands and the positive metal ion.
2666
If we place a metal ion in the center of an
octahedron surrounded by six negative charges –
two types of electrostatic interactions come into
play:
1. There is the attraction between the negatively
charged ligands and the positive metal ion.
2. There is electrostatic repulsion between the ligands
and the electrons in the d orbitals. The magnitude
of this repulsion depends on the particular d
orbital.
2667
If we place a metal ion in the center of an
octahedron surrounded by six negative charges –
two types of electrostatic interactions come into
play:
1. There is the attraction between the negatively
charged ligands and the positive metal ion.
2. There is electrostatic repulsion between the ligands
and the electrons in the d orbitals. The magnitude
of this repulsion depends on the particular d
orbital. For the dx  y orbital, the lobes point along
the x and y axes, where the negative charges are
placed.
2
2
2668
An electron residing in a dx  y orbital would
experience a greater repulsion from the ligands
than an electron in, say the dxy orbital.
2
2
2669
An electron residing in a dx  y orbital would
experience a greater repulsion from the ligands
than an electron in, say the dxy orbital.
2
2
For this reason, dx  y is raised in energy (made less
stable) while dxy, dxz, and dyz are lowered in energy.
The dz is also raised in energy – because its lobes
are pointed at the ligands along the z axis.
2
2
2
2670
Review
2671
2672
As a result of metal ion-ligand interactions, the
equivalence (in energy) of the five d orbitals is
removed to give two high-lying levels: dx  y and dz
of the same energy and three low-lying levels dxy,
dyz, and dxz of the same energy.
2
2
2673
2
As a result of metal ion-ligand interactions, the
equivalence (in energy) of the five d orbitals is
removed to give two high-lying levels: dx  y and dz
of the same energy and three low-lying levels dxy,
dyz, and dxz of the same energy.
2
2
2
The energy difference between these two sets of d
orbitals is called the crystal field splitting. Its
magnitude depends on the metal and the nature of
the ligands.
2674
The best way to measure the crystal field splitting is
by spectroscopic techniques (the absorption
spectrum for example)
hc
ΔE  h 

where ΔE is the energy gap (crystal field splitting),
h is Planck’s constant, h = 6.626 x 10-34Js,  is the
frequency of the photon, and  is the wavelength.
2675
2676
The absorption spectrum of Ti(H2O)63+ . The solution
of this complex ion is purple.
2677
By using a number of different ligands with the same
metal ion the crystal field splitting can be measured
and the spectrochemical series established.
2678
CO and CN- are called strong-field ligands because
they cause a large splitting of the d orbitals. Cl- and
Br- are weak-field ligands – they cause only a small
splitting of the d orbitals.
2679
CO and CN- are called strong-field ligands because
they cause a large splitting of the d orbitals. Cl- and
Br- are weak-field ligands – they cause only a small
splitting of the d orbitals.
The magnitude of the crystal field splitting
determines the magnetic properties of the complex.
2680
CO and CN- are called strong-field ligands because
they cause a large splitting of the d orbitals. Cl- and
Br- are weak-field ligands – they cause only a small
splitting of the d orbitals.
The magnitude of the crystal field splitting
determines the magnetic properties of the complex.
For Ti(H2O)63+, the single d electron must be in one
of the three lower orbitals and the ion is always
paramagnetic.
2681
CO and CN- are called strong-field ligands because
they cause a large splitting of the d orbitals. Cl- and
Br- are weak-field ligands – they cause only a small
splitting of the d orbitals.
The magnitude of the crystal field splitting
determines the magnetic properties of the complex.
For Ti(H2O)63+, the single d electron must be in one
of the three lower orbitals and the ion is always
paramagnetic.
Paramagnetic: The tendency of a species with
unpaired electrons to be attracted by an external
magnetic field.
2682
When there are several d electrons different
possibilities arise. Consider FeF63- and Fe(CN)63-.
Each complex ion has 5 d electrons (for Fe3+).
2683
According to Hund’s rule, maximum stability is
reached when the five electrons enter five separate
d orbitals with parallel spins. This arrangement
requires an energy investment: in the presence of
ligands, two of the five electrons must occupy the
dz and the dx  y orbitals. Because F- is a weakfield ligand, that is, there is a small energy gap
between the upper and lower d orbital energy
levels, the five d electrons enter separate d orbitals
with parallel spins to create a high-spin complex.
2
2
2
2684
On the other hand, CN- is a strong-field ligand, so
it is energetically preferable to have all five
electrons in the lower orbitals – and a low-spin
complex is formed.
2685
The energy gap is small.
FeF63high spin
Fe3+
2686
Fe(CN)63Low spin
The energy gap is large.
Fe3+
2687
Exercise 1: Would you expect both of the complex
ions CoI63- and Co(CN)63- to be paramagnetic?
Exercise 2: Would you expect both of the complex
ions Fe(H2O)62+ and Fe(CN)64- to be paramagnetic?
2688
The case of tetrahedral geometry
The splitting pattern for the tetrahedral case is just
the reverse of that for the octahedral complexes. In
this case the dxy, dxz, and dyz orbitals are more
closely directed at the ligands.
2689
2690
The case of square planar geometry
The splitting pattern for the square planar case is a
bit more involved. You can think of the square
planar case as arising from the octahedral case with
the removal of the two ligands along the z axis.
2691
The case of square planar geometry
The splitting pattern for the square planar case is a
bit more involved. You can think of the square
planar case as arising from the octahedral case with
the removal of the two ligands along the z axis.
With no z-axis interactions present, the dz orbital
energy shows a significant decrease, and the d
orbitals with a z component, dxz and dyz also
decrease in energy (to the same extent).
2
2692
2693
Sample problem: If the ions Al3+, Zn2+, and Co2+
were placed in octahedral environments. Which can
absorb visible light and thereby exhibit color?
2694
Sample problem: If the ions Al3+, Zn2+, and Co2+
were placed in octahedral environments. Which can
absorb visible light and thereby exhibit color?
The electronic configuration of Al3+ is 1s22s22p6.
Because it has no outer d electrons, electronic
transitions will not occur in the visible, so it is
colorless.
2695
Sample problem: If the ions Al3+, Zn2+, and Co2+
were placed in octahedral environments. Which can
absorb visible light and thereby exhibit color?
The electronic configuration of Al3+ is 1s22s22p6.
Because it has no outer d electrons, electronic
transitions will not occur in the visible, so it is
colorless.
The Zn2+ ion has the electronic configuration
1s22s22p63s23p63d10. In this case the 3d orbitals
are filled. There is no room for the dx  y or dz
orbitals to accept an electron from a lower dxy, dxz
or dyz orbital. The complex is therefore colorless.
2
2
2
2696
The Co2+ ion has the electronic configuration
1s22s22p63s23p63d7. In this case there is room for
the movement of a d electron from one of the
lower energy dxy, dxz, or dyz orbitals, into the higher
energy dx  y or dz orbitals.
2
2
2
2697
The Co2+ ion has the electronic configuration
1s22s22p63s23p63d7. In this case there is room for
the movement of a d electron from one of the
lower energy dxy, dxz, or dyz orbitals, into the higher
energy dx  y or dz orbitals. The complex is
therefore expected to be colored, and that is
experimentally observed.
2
2
2
2698
THE END
Time for review
2699
Summary of Key Problem Types
Thermochemistry/Thermodynamics
1. Calculation of enthalpy changes:
a. Heat of reaction
b. Heat of formation
c. Enthalpy change for a phase transition
d. Enthalpy of combustion
e. Heat of solution
2700
2. Hess’ Law problems.
3. Calorimetry calculations:
Determine the enthalpy change for a process
from a measured temperature change.
4. Calculations using the First Law of
Thermodynamics – involving work, heat, and
internal energy.
5. Calculation of entropy changes from standard
entropy values.
2701
6. Calculation of the Gibbs energy from enthalpy
and entropy changes (at a given temperature).
7. Analysis of the equation ΔG  ΔH - T ΔS to
determine when a reaction will be spontaneous.
Conditions for a reaction to be spontaneous.
8. Equilibrium calculations involving ΔG  ΔH - T ΔS ,
e.g. determine the enthalpy change, the
temperature, or the entropy change for a phase
transition given two of these variables.
2702
Kinetics
9. Approximate calculation of the rate of reaction
given the time interval and the change in
concentration of a species.
10. Determination of an accurate rate using the
slope method from a concentration vs. time plot.
11. Calculation of the reactant order in a rate law
expression.
2703
12. Calculations of concentrations, rate constants,
half-lives for zero-order and first-order reactions.
Calculation of time required for a certain
concentration to be reached (radioactive method
to date objects).
13. Calculation of the rate constant from a plot of
ln([A]0/[A]t) vs. time (for first-order reactions).
2704
14. Calculations using the Arrhenius equation:
a. Determination of Ea
b. Determination of k
c. Determination of T
d. Graphical methods
15. Writing rate law expression from elementary
steps.
2705
Chemical equilibria – general
16. Writing expressions for equilibrium constants
and reaction quotients for chemical reactions
involving solids, liquids, and gases.
17. Use of the ideal gas equation PV = nRT to go
from Kc to Kp or from Kp to Kc.
18. Multiple equilibria – product of the equilibrium
constants gives the overall equilibrium constant
for the combined reaction.
2706
19. Calculation of the equilibrium concentrations
given K and the initial concentrations. (ICE table
problems).
a. Approximate solution approach.
b. Quadratic equation approach.
20. Problems involving LeChatelier’s principle.
a. Concentration changes
b. Temperature changes
c. Pressure changes
2707
21. Calculation of ΔG away from equilibrium.
22. Calculation of K given ΔG0 , or the calculation of
ΔG0 given K.
23. Solubility product calculations
a. Calculation of Ksp.
b. Calculation of solubility.
c. Common ion effect calculations.
d. Calculation of when precipitation will occur.
e. Simple approximations to employ.
2708
Acid-Base Equilibria
24. pH Calculations.
a. Strong acids, b. strong bases, c. weak acids,
d. weak bases, e. mixtures of acids + bases.
25. Equilibrium calculations involving Ka and Kb.
Calculation of per cent dissociation.
26. Equilibrium calculations involving polyprotic
acids – simple approximations to employ.
2709
27. Salt hydrolysis – calculation of the pH of salt
solutions.
28. Buffer calculations using the HendersonHasselbalch equation.
2710
Electrochemistry
29. Balancing redox equations.
30. Faraday’s law calculations:
a. Calculation of moles of product or reactant.
b. Calculation of time or current to produce
required amount of product.
2711
31. Calculation of standard emf for redox reaction.
32. Calculation of ΔG0 from E0.
33. Calculation of K from E0.
34. Calculation of maximum (non-expansion) work
for a cell.
35. Prediction of spontaneous direction for a redox
reaction.
2712
36. Calculations involving the Nernst equation.
2713