1. The ^max = 420 nm for [Co(NH3)6]3+.
Assume P= 18,000 cm-1.
Calculate the So and CFSE in kJ/mol for this complex.
(Recall the relationship between wavelength (nm) and wavenumber (cm-1) and that
1.1962 x 10-2 X E (cm-1)= = E (kJ/mol).
2. Three flasks have been mixed up in the lab. (Unfortunately, this really happens in research!)
The three flasks contain solutions of three different colors: green, pink, and yellow.
It is also known that:
one flask contains [Ti(H2O)bl+:
another flask contains [Cr(NH3)6 ,13+;
the third flask contains
To try to determine which complex is in which flask, you have taken the visible electronic spectrum of
all three solutions and your data is below:
Flask A: ^max at energies 8,500, 15,200, 25,000 cm-1
Flask B: ^max at energies 20,000, 27,500, 38,000 cm-1
Flask C: 2max at energy 20,300 cm-1
Which complexes are in flasks A, B and C? Explain your reasoning!
3. In a previous class, a student showed the molecule below during her elemental exhibit on gold, Au.
The empirical formula is [Au4Clg] which might be interpreted as a tetramer cluster of four Au(2+).
However, she said the actual structure is that shown below, and the oxidation states should be assigned
as two Au(+) and two Au(3+) ions, as shown in the structure below.
What one experimental measurement would be able to distinguish a structure of four Au(2+) ions from
a structure of two Au(+) and two Au(3+) ions?
4. Describe the kind of interaction is depicted in the image at right
What label would you apply to this interaction?
5. Chromium is a metal of many colors! One green pigment used in paints, as well as in
eyeshadows, is chrome green, Cr203. However, chromium takes on a different hue in the yellow
pigment chrome yellow, [Pb+2j[cr04-2). Note that for chrome green the Cr ion is surrounded
by six oxide 02- ions with an octahedral geometry in the sólid state structure of chrome green.
a) Is the color of chrome green produced by the same type of electronic transition that causes the
color of chrome yellow?
b) Predict the relative saturation (i.e., absorptivity or extinction coefficient) of chrome green
versus chrome yellow. Defend your answers with detailed explanations.
6. Zinc enzymes have no "spectroscopic handle", that means, there is no electronic spectral data,
to help monitor their behavior in studies of zinc enzyme mechanisms. Why not?
7. A compound of molecular composition is Ni(CIO4)2(py)4 has two forms: one is a blue form
having a 2.87 B. M. magnetic moment, and the other is a diamagnetic yellow form.
Draw the structures of the two forms, explaining how they are consistent with the data. (py =
pyridine). Note that perchlorate, (CIO4)-, is a very poorly coordinating anion.
8. Use CFT to explain why Cr(3+) makes only octahedral geometry complexes with strong and
weak field ligands while Fe(2+) makes both octahedral and tetrahedral complexes with weak field
9. Which complex below will have the fastest rate of aquo ligand exchange in water and why?
Which complex below will have the slowest rate of aquo ligand exchange in water and why?
10. The hybrid orbital Pa is composed of 60% 3dx2.y2 and 40% 4py.
a) Draw the hybrid orbital Pa.
b) What are the values of C1 and C2?
c) Is the hybrid normalized? Support your answer with an argument.
d) Draw the hybrid orbital, Db, that is a partner to Pa and write its mathematical expression.
e) Are the two hybrids, Pa and Db, orthogonal? Support your answer with an argument.
11. For the aquation reaction (substitution of X by water) of (Ni(NH3)5X]n+ where X is Cl. F. H2O,
SCN-, the reaction rate shows no effect as X is varied. The mechanism that is suggested by this
12. (a) For draw all possible diastereomers.
(b) For [Co(en)2(Br)2]+ draw all the optical isomers.
13. In the reaction of with thiocyanate, NCS-, the kinetic product is
where the Co binds to the S atom, and the thermodynamic product is
where the Co binds to the N atom. Provide an argument for why the [Co(NH3)5(-
complex is the thermodynam product.
This material may consist of step-by-step explanations on how to solve a problem or examples of proper writing, including the use of citations, references, bibliographies, and formatting. This material is made available for the sole purpose of studying and learning - misuse is strictly forbidden.