1. Propylene Sulfide - C2H4S
Expected reactivity??
Purpose??
Source of sulfur, formally S0

2. ? What happens in reactions with Mo complexes? + S characteristics:
Mo(4+): could be oxidized or reduced
open (vacant) coordination site
Mo loves S
characteristics:
Mo(6+):
filled coordination sphere
Mo loves S
Seems OK but is it right?
How could we know for sure?????

3. Before deciding, you need to know about sulfur:
Sulfur is strange!!!!
That’s why the alchemists loved it. They thought that everything, every substance
could be made from the “proper” mixture of sulfur, mercury and salt.
Sulfur does not behave like its smaller cousin, O.
Elemental form: S vs. O=O
As ions: S2- & [S2]2- O2- & [O2]2- & [O2] -
polysulfides [S3]2- & [S5]2-
As ligands: M=S M(S2) M(S3) M(S4) M(S5)
disulfide trisulfide tetrasulfide pentasulfide

4. Infrared Spectroscopy helps assign sulfur ligand type:
M=S has nM=S ~ cm-1
M(S2) has nM-S ~ cm-1
M(S3), M(S4) has nM-S < 480 cm-1
Let’s try it …

5. [Tp*Mo(X)(S4)]—
What is X?

6. compound was determined to be [Tp*Mo(S)(S4)]—
B-H
C=N
C-H
O-H
ring

7. Product was determined to be
a mixture of both
[Tp*Mo(S)(S4)]— and
[Tp*Mo(O)(S4)]—
Mo=S
Mo=O

8. A B What’s the difference between pictures A and B?
from X-ray crystallography
from Chem 3D; “guessed” structure

9. UV/vis Spectroscopy = Electronic Spectroscopy
What does it monitor / probe?
What information about molecule can one obtain?

10. 1H NMR: what do you expect to see?

13. a a b b c c
Expected: 3 resonances, 2 -CH3 (a & c with 6H) and 1 H (b)
( B-H not visible due to broadening)
… plus H’s on cation TEA = [N(CH2CH3)4]+

14. 1H NMR: what do you expect to see?
[Tp*Mo(S)(S4)]—

16. e d
Mo=S
Mo=O f a b c
TEA+
-CH3
TEA+
-CH2-

17. d e
Mo=S
Mo=O f a b c a
TEA+
-CH3 c b
TEA+
-CH2- a c b d e f

18. R1 ≠ R2: How many H’s expected in NMR from pyrazole rings?
All -methyl and ring H’s will be unique: see 6 -Me and 3 ring H