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

? 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?????

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: S8 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

Infrared Spectroscopy helps assign sulfur ligand type: M=S has nM=S ~ 450-500 cm-1 M(S2) has nM-S ~ 500-550 cm-1 M(S3), M(S4) has nM-S < 480 cm-1 Let’s try it …

[Tp*Mo(X)(S4)]— What is X?

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

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

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

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

1H NMR: what do you expect to see?

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]+

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

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

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

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