Download ADVANCED INORGANIC CHEMISTRY December 6, 2006 QUIZ 4

ADVANCED INORGANIC CHEMISTRY
December 6, 2006
INSTRUCTIONS:
PRINT YOUR NAME ————> NAME
QUIZ 4
.
WORK ALL 5
TOTAL = 100
SHOW YOUR WORK FOR PARTIAL CREDIT
USE THE CORRECT NUMBER OF SIGNIFICANT FIGURES
THE LAST TWO PAGES ARE A PERIODIC TABLE AND A SCRATCH SHEET
QUIZ 4
R = 0.08206 lit-atm/mol-K
R = 8.3145 J/mol-K
h = 6.626 X 10-34 J-s
1
2
10
15
3
25
c = 2.9979 X 108 m/s
4
25
5
25
J = (kg-m2)/s2
TOTAL(100)
QUIZ 5
R = 0.08206 lit-atm/mol-K
R = 8.3145 J/mol-K
h = 6.626 X 10-34 J-s
1
2
25
25
3
25
c = 2.9979 X 108 m/s
4
J = (kg-m2)/s2
TOTAL(100)
25
25
1. Several species of diatomic molecules and ion are formed between C and N. The
molecular orbital diagram is that for diatomic with s-p mixing. Consider the following
species CN+, CN, and CN-.
(a) Draw the molecular orbital diagram that is appropriate for these species. You only
need to draw one diagram showing the energy levels, but label the orbitals with
σ, σ∗, π, and π∗
(b) Draw the shape of the lowest σ orbital. Which atom contributes the greatest character
to this orbital?
(c) Draw the shape of one of the π* orbitals. Which atom contributes the greatest
character to this orbital?
(d) Calculate the bond order of the three species.
CN+
CN
CN-.
(e) which species has the longest bond distance? _____________
Which has the greatest bond energy?____________________
2. Suggest an appropriate hybridization scheme for the central atom of the following
molecules of ions:
(a) PF5
(b) XeF4
(d) OCN-
(e) H2CO
(C atom is central
(C atom is central
(c) PF3
(f) O2
3.
The bonding in the molecule PF5 (D3h point group) can be described by molecular orbital
theory. (This problem goes over two pages)
z
Location of symmetry elements
F
F
C3 S3 – z axis
F
C2 – along each P-F bond (x axis is one)
P
F
x
σh – xy plane
σv - plane of 2 axial F’s and one
equatorial F (xz plane is one)
F
y
If we consider only the sigma bonding we can use the s orbitals on F to form a reducible
representation to form group orbitals. Fill in the table for the reducible representation, Γ, below
by performing the symmetry operations and counting the number of s orbitals that do not move. I
have filled in the first value. (Hint when you sum all the characters the total is 14)
Transfer reducible representation to the next page.
P
(x axis coincident with C'2 axis)
2C3 (z) 3C'2
A'1
+1
+1
+1
+1
+1
+1
-
x2+y2, z2
A'2
+1
+1
-1
+1
+1
-1
Rz
-
E'
+2
-1
0
+2
-1
0
(x, y)
(x2-y2,
xy)
A''1
+1
+1
+1
-1
-1
-1
-
-
A''2
+1
+1
-1
-1
-1
+1
z
-
E''
+2
-1
0
-2
+1
0
(Rx, Ry)
(xz, yz)
E
2C3 (z) 3C'2
2S3
3
D3h
5
h
h(xy)
3
quadrati
c
functions
E
D3h
(xy) 2S3
linear functions,
rotations
v
v
3. (continued)
2C3 (z) 3C'2
A'1
+1
+1
+1
+1
+1
+1
-
x2+y2, z2
A'2
+1
+1
-1
+1
+1
-1
Rz
-
E'
+2
-1
0
+2
-1
0
(x, y)
(x2-y2,
xy)
A''1
+1
+1
+1
-1
-1
-1
-
-
A''2
+1
+1
-1
-1
-1
+1
z
-
E''
+2
-1
0
-2
+1
0
(Rx, Ry)
(xz, yz)
E
2C3 (z) 3C'2
2S3
3
h
h(xy)
3
quadrati
c
functions
E
D3h
(xy) 2S3
linear functions,
rotations
v
v
D3h
5
Reduce this representation to a sum of irreducible representations of the point group.
Do not forget the number of symmetry operators in each term.
4. Identify which possible atomic orbitals (s and the three p orbitals and five d orbitals)
on P interact with the group orbitals with the symmetries that you found in problem # 3.
3
quadrati
c
functions
2C3 (z) 3C'2
A'1
+1
+1
+1
+1
+1
+1
-
x2+y2, z2
A'2
+1
+1
-1
+1
+1
-1
Rz
-
h
(xy) 2S3
linear functions,
rotations
E
D3h
v
E'
+2
-1
0
+2
-1
0
(x, y)
(x2-y2,
xy)
A''1
+1
+1
+1
-1
-1
-1
-
-
A''2
+1
+1
-1
-1
-1
+1
z
-
E''
+2
-1
0
-2
+1
0
(Rx, Ry)
(xz, yz)
E
2C3 (z) 3C'2
2S3
3
D3h
5
h(xy)
v
5. The following two ligand orbitals can be used to form a π bonds to the central
atomic orbitals on the P atom in PF5.
P
A
B
Orbital A is one of two orbitals that belong to the E’’ irreducible representation.
Orbital B belongs to the A’’2 irreducible representation.
3
quadratic
functions
2C3 (z) 3C'2
A'1
+1
+1
+1
+1
+1
+1
-
x2+y2, z2
A'2
+1
+1
-1
+1
+1
-1
Rz
-
E'
+2
-1
0
+2
-1
0
(x, y)
(x2-y2, xy)
A''1
+1
+1
+1
-1
-1
-1
-
-
A''2
+1
+1
-1
-1
-1
+1
z
-
E''
+2
-1
0
-2
+1
0
(Rx, Ry)
(xz, yz)
h
(xy) 2S3
linear functions,
rotations
E
D3h
v
(a) Which d orbital on P does group orbital A interact with? Draw the bonding and
antibonding combinations. Although theoretically possible, these orbitals are not
important in bonding.
(a) Which p orbital on P does group orbital B interact with? Draw the bonding and
antibonding combination.
Useful Data about ligands
Weak field ligands - F-, Cl-, Br-, I-, H2O
Strong Field Ligands- NH3, CN-, NO2-, en = (H2N-CH2-CH2-NH2 , bind through both N
atoms)
Structural Isomer types
Ionization – Interchange of an anionic ligand bound to the central metal with in one in
the crystal
Hydration – Interchange of a water molecule bound to the central metal with another
ligand in the crystal
Coordination – Both cation and anoin are complex ions. The two metals interchange at
least one ligand
Linkage – A ligand is bound to the metal through different bonding modes
Steroisomerl Isomer types
Geometrical – The connectivity to ligand is the same, but the arrangement in space
differs (For example cis and trans isomers)
Optical – Isomers that are not superimmposable of their mirror image.
1. Draw the structures of the following compounds. Species outside the brackets are not
bound to the central metal, but are in the crystal.
(b) [Co(NH3)3Cl3](NO2)3
(a) [Co(NH3)6] [Cr(NO2)6]
mer isomer
(c) [Co(NH3)3(NO2)3] (Cl3)
mer isomer
(e) [Cr(NH3)6] [Co(NO2)6]
(d) [Cr(NH3)3(H2O)3] (NO2)3 fac isomer
(f) [Cr(NH3)3(H2O)3] (NO2)3 mer isomer
(g) (a) [Cr(NH3)3(NO2) 3] ·3 (H2O) any isomer
(f) Identify the types of isomers for the following pairs from (a)-(g).
(a) and (e) ________________
(d) and (f)______________
(b) and (c) ________________
(d) and (g)______________
(f) aqnd (g) ________________
2. In the molecular orbital treatment of an octahedral complex metal we found that the d
orbitals split in the presence of the ligands into two sets with the following energy level
order:
______
_____ eg
______ ______ ________ t2g
Determine the orbital occupancies for the following species, and the number of unpaired
electrons
Orbital occupancies
______
_____
(a) [Co(H2O)6]2+
______ ______ ________
______
_____
3-
(b) [Fe(CN)6]
______ ______ ________
______
_____
3+
(c) [Cr(NH3)6]
______ ______ ________
______
_____
(d) [Co(en)3]3+
______ ______ ________
______
_____
(d) [Mn(CN)6]3______ ______ ________
# unpaired
electrons?
estimate µ
(spi only)
3. (a) Briefly define or describe crystal (or ligand) field stabilization energy.
(b) Calculate the crystal (or ligand) field stabilization energies for a d6 complex in terms
of ∆o for both the low spin and high spin cases.
(c) What is the deciding factor according to your calculation in (b) as to whether a
complex will be high spin or low spin?
(d) Why are there no low spin tetrahedral complexes. (the answers in (c) and (d) are
related.)