organometallic general properties

1. Organometallic
Chemistry
Dr. Ravindra Shinde
Dayanand Science College, Latur
B.Sc- Second year (Sem-III)
Sub: Chemistry
Paper-VI: Organic chemistry

2. Organometallic Compounds
• Compounds that contain a Metal-Carbon bond.
• Metal Alkyls, e.g. Tetraethyllead - Leaded Gas
• Alkyl = methyl, ethyl, tert-butyl, etc.
• Metal = Li, Na, K (alkali metals)
Mg (alkaline earth metals)
Ti Cr Mn Fe Co Ni Cu Zn
Zr Ru Pd Hg
OS Pt

3. Metal Alkyls
• General formula R-M (R = alkyl, M = metal)
• The C-M bond is a covalent bond!
• However, C--M+ or R--M+ bond tend to be polarized.
• This is especially true for organometallic
compounds conataining the more electropositive
metals, i.e. alkali and alkaline earth metals.
• Generally, the alkyl fragment of the organometallic
compound is very reactive; however this depends on
the metal, changing the metal alters the polarization
of the R-M bond.
• Thus different organometallic compounds are used
in many different types of organic reactions.

4. Useful Metal Alkyls in Organic Synthesis
C-M Bond
• Organomagnesium – Mg (C--Mg+)
• Organolithium - Li (C--Li+)

5. Organomagnesium Compounds
• Methylmagnesium chloride - CH3Mg+ Cl-
• Ethylmagnesium bromide - CH3CH2Mg+ Cl-
Draw the structures of:
• Isopropylmagnesium iodide
• Sec-butylmagnesium chloride
Formation of Grignard Reagents:
CH3-Cl CH3Mg Cl
Grignard Reagents
Mg, Et2O

7. Synthetic application of
Methyl Magnesium bromide

8. 1. Reaction with formaldehyde
• Addition of a Grignard reagent to formaldehyde
followed by H3O+ gives a 1° alcohol
• This sequence (mechanism) is general and important!
Mg
+2
H3O
+
CH3CH2
-
MgBr
+
H
C
H
O CH3CH2 C
H
H
O
-
MgBr
+
CH3CH2 C
H
H
OH +
THF dil.

9. Mg
+2
H3O
+
CH3CH2
-
MgBr
+ CH3CH2 C O
-
MgBr
+
O
+
THF dil.
CH3CH2 C OH
O
C O
O
2. Reactions with CO2
These are valuable and important reactions…
Please add to your card stock!

10. 3. Grignard reagents react with esters
R
MgX
C
O
••
•
• –
MgX
+
d– d+
R C
O
••
•
•
•
•
diethyl
ether
OCH3
••
•• OCH3
••
••
R'
R'
but species formed is
unstable and dissociates
under the reaction
conditions to form a ketone

11. Grignard reagents react with esters
R
MgX
C
O
••
•
• –
MgX
+
d– d+
R C
O
••
•
•
•
•
diethyl
ether
OCH3
••
•• OCH3
••
••
R'
R'
–CH3OMgX
C
O
R R'
•
•
••
this ketone then goes on
to react with a second
mole of the Grignard
reagent to give a tertiary
alcohol

12. Example
2 CH3MgBr + (CH3)2CHCOCH3
O
1. diethyl ether
2. H3O+
(CH3)2CHCCH3
OH
CH3
(73%)
Two of the groups
attached to the
tertiary carbon
come from the
Grignard reagent

13. 4.Reaction of Grignard Reactions
with Water

14. 5. Reaction of Grignard Reactions
with Epoxide

15. 6. Reaction of Grignard Reactions with
Acetaldehyde

16. 7.Reaction of Grignard Reactions
with Acetone

17. 8.Reaction of Grignard Reactions
with Acetyl chloride

18. 9. Reaction of Grignard Reactions
with alkyl CN

19. 10. Reaction of Grignard Reactions
with Methy formate

20. 11. Reaction of Grignard Reactions
with ethy acetate

21. 12.Reaction of Grignard Reactions
with chloroformate

22. Organolithium Compounds
• Methyllithium – CH3Li
• Ethyllithium - CH3CH2Li
• Organo Lithium Compounds are more reactive than
magnesium analoges.
Preparation of organolithium reagents:
1. CH3-Br CH3Li + LiBr
2. C6H5-Br + C4H9Li C4H9-Br + C6H5Li
Alkyl Lithium Compounds
2 eq. Li, Et2O

23. Reaction of organo lithium
compounds
• Reaction with Water and Ethanol
• CH3-LI + H2O → CH4 + LiOH
Methyl Methane
Lithium
• CH3-LI + C2H5OH → CH4 + LiOC2H5
Methyl Methane
Lithium

25. Organo Zinc compounds