Exercises_Exam_II_material

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Chemistry 4610/5560, Dr. Mohammad Omary
Inorganic Chemistry, Fall, 2004
Department of Chemistry, University of North Texas
Problems Bank for Exam 2 Material
Chapter 6 Material:
(1) Determine the relative solubility of PbCl2, PbBr2, and PbI2.
(2) In IF5 solvent, SbF5 acts as an acid while KF acts as a base. Explain and write balanced chemical
equations to justify your answer.
(3) HCN behaves as an acid with diethyl ether but as a base with SbF5. Explain and sketch suitable
structures to justify your answer.
(4) Among group 12 metals, zinc and cadmium occur as both sulfides and oxides. Mercury, on the other
hand, exists most commonly only as sulfide (HgS, known as cinnabar).
(5) Aqueous solutions of the following oxides lead to the formation of hydroxide species (M-O-H). The
resulting B2O3 solutions are acidic, Sc2O3 solutions are basic, while Al2O3 solutions are amphoteric (i.e., have
both acidic and basic properties). Explain.
(6) Naphthalene solutions emits UV light. When silver ions are added (e.g., AgClO4), a white precipitate
formed that has a green emission. NMR and IR data suggest that the naphthalene units are intact with no loss
of aromaticity or hydrogen or carbon atoms. Explain the kind of interaction might have taken place between
naphthalene and silver perchlorate.
Chapter 9 Material:
(1) Answer the following questions about the complex Cr(CO)2(CN)2(NH3)2:
a. Name the complex.
b. Draw all possible geometric isomers and indicate which isomers are chiral (for chiral isomers, do NOT
draw their mirror images; just indicate that they are chiral).
c. If the infrared spectrum of a compound with the above formula shows two vC-O bands and one vC-N band,
identify the actual structure amongst the isomers you have drawn above. Explain.
(2) a. Name the compounds [Re(CO)3(en)Br], [Pt(NH3)3Cl3]Cl, [Co(en)3]Cl2, and [Ru(SCN)2(bipy)2](NO3)2
b. Draw ALL possible geometric isomers for the complex in each compound and indicate which are
chiral (for chiral isomers, do NOT draw their mirror images; just indicate that they are chiral).
(you may use N
N to represent "en" and "bipy"):
(3) Draw the structure of di--carbonylbis(tricarbonylcobalt)(0).
(4) The same dithiophosphonate (dtp) ligand below exists in different modes in different coordination
compound, as seen in the following scheme from a recent paper for Dr. Omary (Inorg. Chem. 2003, 42,
5311-5319). Determine the mode(s) of the dtp ligand in each of compounds 1-6 in this scheme.
OR'
R
P
S
S
Ph3P
Au
PPh3
R
3
Au OR'
S P R
Au
S
P
S
OR'
1 dppm
2
Ph P
Ph
S
PR
OR'
P Ph
Ph
4
4 PPh3
1 dppm
2 dppm
HBF4
R
R'O
CH2Cl2/ether
P
S
Au
S
S
Au
S
P
H3C
S
S
dtp-
Au
Au
Et2O
+
Ph
P Ph
Ph
P
Ph
Ph
P Ph
Ph
Ph P
O
Ph
P Ph
Ph
P
Ph
S
1
Ph P
Ph
+
BF4-
Au
Au
O
CH2Cl2/n-hexane
+
S
R
P OR'
P Ph
Ph
Heat
Ph
P
Ph
Au
Ph P
Ph
5
BF4Ph
P Ph S R
P
Au
OR'
S
Ph
P
Ph
6
dtp = dithiophosphonate = [S2P(R)(OR')]- with R= p-C6H4-OCH3; R'= c-C5H9
Chapter 10 Material:
PART I. Multiple-choice:
1. Which statement most correctly describes crystal field theory for a d block complex of unspecified
geometry?
a. The theory considers covalent interactions between a metal centre and the surrounding ligands.
b. The theory considers electrostatic interactions between a metal ion and the surrounding ligands which
are taken to be point charges.
c. The theory rationalizes the non-degeneracy of the metal d orbitals by considering the electrostatic
repulsions between point charge ligands and electrons in the metal d orbitals.
d. The theory rationalizes why the metal d orbitals are split into two levels.
2. Which of the following correctly places the ligands in their order in the spectrochemical series?
a. Br– < Cl– < NH3 < H2O
b. I– < Br– < H2O < [OH]–
c. F– < Cl– < H2O < NH3
d. I– < Cl– < H2O < en
3. Which of the following correctly places the metal centers in order of increasing field strength?
a. Mn(II) < Fe(III) < Rh(III)
b. Co(III) < Co(II) < Rh(III)
c. Pt(IV) < Pd(II) < Ni(II)
d. Pd(II) < Ni(II) < Pt(IV)
4. Which of the following complex ions is tetrahedral?
a. [PdCl4]2–
b. [PtCl4]2–
c. [NiCl4]2–
d. [AuCl4]2–
5. Match up the correct formula and magnetic property. Which pair is correct?
a. [Zn(H2O)6]2+; paramagnetic
b. [Co(NH3)6]3+; diamagnetic
c. [CoF6]3–; diamagnetic
d. [V(H2O)6]2+; diamagnetic
PART II. Problems
1. According to the crystal field theory, the five d orbitals, which are degenerate in a free ion, become no
longer degenerate when a transition metal ion is placed in a ligand field environment.
a. Predict the splitting of d-orbitals in both tetrahedral and octahedral environments.
Free ion
Octahedral
Tetrahedral
dxy dxz dyz dz2 dx2-y2
b. Compare the largest crystal field splitting in octahedral (o) vs. tetrahedral (t) complexes; and in
tetrahedral (t) vs. square planar (1) complexes.
c. Predict the highest-energy orbital or group of orbitals among the five d orbitals when a transition metal ion
is placed in the following types of ligand field environments (assuming conventional axes definition is used):
a. Square planar:
b. Trigonal bipyramidal:
c. Linear:
2. Predict the correct hybridization for the metal ion in the following complexes, based on the concepts of the
valence bond theory.
a. a diamagnetic d6 octahedral complex.
b. a paramagnetic d6 octahedral complex.
c. a diamagnetic d8 square planar complex.
d. a paramagnetic d5 tetrahedral complex.
e. a linear 2-coordinate d10 complex.
3. Use the concepts of crystal field theory to predict the d-orbital splitting in:
a. octahedral complexes
b. tetrahedral complexes
c. trigonal bipyramidal complexes
d. square planar complexes
4. Use the concepts of ligand field theory to construct the -bonding scheme for:
a. octahedral complexes (Oh)
b. tetrahedral complexes (Td)
c. square planar complexes (D4h)
5. Answer the following questions for all complexes below:
a. Name each complex.
b. Sketch the electronic distribution of the d electrons in the crystal field orbitals for the appropriate
geometry of each complex. If there is a possibility for high-spin or low-spin configuration, explain
your selection.
i.
[Cr(H2O)6]2+
ii.
[Cr(H2O)6]3+
iii.
[FeCl4] -
iv.
[Fe(CN)6]3-
v.
[Ni(SCN)4]2-
vi.
[Cu(en)2(H2O)2]2+
vii.
[CoF6]3–
viii.
[IrF6]3-
ix.
[Co(en)3]2+
x.
[Rh(en)3]2+
xi.
[Co(bpy)3]3+
xii.
[Co(CO)4]–
6. Make up a spectrochemical series from the following ligands (i.e., arrange their relative field strength):
Cl–, NH3, CO, -SCN-, -NCS-, H2O, en, CN-.
7. Predict whether the following 4-coordinate complexes are likely to be square planar or tetrahedral:
a. [NiCl4]2b. [PtBr4]2–
c. [Ni(CN)4]2d. [Ni(CO)4]
Chapter 11 Material:
(1) Fill the following table for octahedral complexes. Refer to your class notes and the Tanabe-Sugano
diagrams (Figure 11-7).
dn
Ground state
term symbol for
free ion
Ground state term
symbol for complex
Excited state term symbols for allowed
transitions (see note* below)
2
3
4 (HS)
4 (LS)
5 (HS)
5 (LS)
6 (HS)
6 (LS)
7 (HS)
7 (LS)
8
* If there is more than one allowed transition, list them in order of increasing energy.
2) Fill the above table but now for tetrahedral complexes.
dn
Ground state
Ground state term
Excited state term symbols for allowed
term symbol for symbol for complex
transitions (see note* below)
free ion
2
3
4
5
6
7
8
* If there is more than one allowed transition, list them in order of increasing energy.
3) Practice filling the above table but use real octahedral and tetrahedral complexes from among those given
in Problem 5 above about Chapter 10.
4) For each of the configurations of an octahedral complex in Problem 1 above, indicate whether it has
strong, weak, or no Jahn-Teller distortion. Explain why.
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