1. (Father of organometallic
INTRODUCTION
Organometallic compounds are the
Compounds containing a carbon
–metal bond .
Since lithium is a metal , so it forms
an organo-metallic compound.
The compounds formed by
carbon– lithium bonds are called
organolithium compounds
e.g. CH3-Li
‘CH3’ is an organic group
‘Li’ is the metallic group
Dr. HENRY GILMAN
(Father of organometallic
chemistry)

2. DISCOVERY Organolithiumcompounds,
discovered by Wilhelm Schlenk in 1917.
But only since the 1950th, based on the pioneering work of Georg Wittig and Henry Gilman, organometallic reagents became a routinely used tool in the synthetic organic laboratory.
Dr.WILHELM SCHLENK
(German chemist,
( )

3. STRUCTURE AND BONDING - + :
strong base d- d+
good nucleophile
significant (-) charge
at the carbon
57% covalent
43% ionic
Carbon-metal bonds are polar bonds that can be represented by a resonance hybrid of covalent and ionic structures.
C-Li are strong bases and react with acids,
even weak acids like water and alcohols.

4. STRUCTURE AND BONDING C-K 51 C-Na 47 C-Li 43 C-Mg 35 C-Zn 18 C-Cd 15
C-Cu 9
strongest base
best nucleophile
percent ionic
bond
most reactive
least reactive
Li is the
Metal used
most often

5. PREPARATION OF ORGANOLITHIUM COMPOUNDS
The organometallic compounds can be prepared
by following methods:-
By Halogen Metal Exchange
From Terminal Alkynes
By Trans Metalation/ Metal-Metal Exchange
By Directed Metalation/ Ortho Metalation

6. PREPARATION OF ORGANOLITHIUM COMPOUNDS
By Halogen Metal Exchange
Normally prepared by reaction of alkyl halides with lithium R
X + 2Li R
Li + LiX
same for Ar—X
It is an oxidation-reduction reaction: carbon is reduced

7. diethyl ether Examples (CH3)3CLi + LiCl (CH3)3CCl + 2Li –10°C (75%)Br
+ 2Li Li
+ LiBr
35°C
(95-99%)
It is usually chosen for aryl derivatives 11

8. PREPARATION OF ORGANOLITHIUM COMPOUNDS
From Terminal Alkynes

9. PREPARATION OF ORGANOLITHIUM COMPOUNDS
By Trans Metalation/ Metal-Metal Exchange
2Li + R2Hg Li + Hg
In the above equation ‘Li’ metal is replaced by ‘Hg ’
This reaction is preferred to form organolithium
compounds from other organometallic compound.

10. PREPARATION OF ORGANOLITHIUM COMPOUNDS
By Directed Metalation/ Ortho Metalation
DMG
DMG Li
+ R-H
+ RLi
Metallation of an aromatic ring near a substituent, which acts as a “Directed Metallation Group”, is called “Ortho-Metallation”.
They have in common the ability to coordinate the approaching cation
(= lithium-ion) and/or to increase the acidity of the ortho-hydrogen

11. PROPERTIES OF ORGANOLITHIUM COMPOUNDS
Physical properties
Highly polar due to most electro
positivity of lithium group .
Volatile in nature, easily absorbs
moisture.
Solubility in Hydrocarbons .
More complex bonding.
Forms covalent compounds due
to vacant ‘p’ orbital
Polarity of Bonds

12. SOLVENTS THAT ARE FREQUENTLY USED..
diethyl ether ..
THF
tetrahydrofuran .. ..
These solvents do not
react with the metals
themselves or with
the organometallic
compounds formed.
pentane
benzene .. ..
1,4-dioxane .. ..

13. PROPERTIES OF ORGANOLITHIUM COMPOUNDS
Chemical properties
HO-CH2CH2-R
R-CO-CH=CH-R
R-COOH
R1-CO-CH=CH2
R1-CO-R
epoxide
CO2
CuI 2 3 4
R1-COOR2 R
R1-C-OH
R1-X 5
R-Li 1
R1-R 10
R1-CO-R2 6 R2 9 7 8
R-CO-Cl O2
R1-CHO
R1-C=CH
R-CO-R
R-OH
R1-C=C-Li
R-CO-R1

14. REACTIONS OF ORGANOLITHIUM COMPOUNDS
Reaction with water
Water or traces of moisture (water vapor)
destroy the reagent !
R-Li H2O R-H LiOH
strong
base - - + +
The glassware must be dry, and
we must not expose the reagent to humid air.

15. REACTIONS OF ORGANOLITHIUM COMPOUNDS
Reaction with oxygen
Oxygen reacts with alkyllithium compounds to form
hydroperoxides. - + +
H2O
butyllithium
a hydroperoxide
This reaction usually proceeds in low yield,
meaning it is not a good synthetic method .
However, it can be a annoying problem when
trying to prepare alkyllithium compounds.

16. REACTIONS OF ORGANOLITHIUM COMPOUNDS
Removing a Halogen
The reaction with water is a way of reducing ( or dehalogenating )an alkyl halide ( converting C-X to C-H ) .
ether Li
H2O
Removal
of Br + -

17. .. - Li+ .. : : : - REACTIONS WITH THE CARBONYL (C=O) GROUPd- : d+ -
new C-C
bond +
NUCLEOPHILIC ADDITION TO CARBONYL
Since oxygen is more electronegative than carbon, the carbonyl group is electron-deficient at carbon, that is, it is an electrophile.
The organometallic compound (R-Li) behaves as a nucleophile with an unshared pair on the carbon.

18. SYNTHESIS OF ALCOHOLS
Reaction of RLi with aldeydes and ketones yields alcohols. +
formaldehyde
primary alcohol +
other aldehydes
secondary alcohol +
ketones
tertiary alcohol
The type of alcohol depends on whether we use formaldehyde,
another aldehyde, or a ketone.

19. SYNTHESIS OF A CARBOXYLIC ACID.. : Li
dry-ice d+
ether : .. d- .. :
H3O+
Slow step .. - + : Li ..
H3O+
CO2 Li
R-Br R-Li R-COO- Li R-COOH
usually dil. HCl

20. REACTION OF ,-UNSATURATED CARBONYL COMPOUNDS WITH ORGANOMETALLIC REAGENTS
C6H5Li
C6H5CH=CHCOC6H C6H5CH=CH-CHO
When an organolithium compound react with an ,-unsaturated carbonyl compounds it gives 1,2 addition product

21. RECENT DEVELOPMENTS
Lithium hexamethyldisilazide (LHMDS) lithium amide,
30 % solution in hexane
Mol. Formula: C6H18LiNSi2
Application: Selective low nucleophilic base for e.g. enolisations
Appearance: yellowish solution
Physical Properties:
Molecular weight:
Density: 0.71 g/ccm (at 20°C)
Boiling point: 60 – 80 °C for Hexane

22. LIMITATIONS OF ORGANOLITHIUM COMPOUNDS
Highly volatile , so not used in mild reaction .
It easily absorbs moisture , because of which it is not kept in open envoirnment.
These compounds are harmful for skin. so, we should use gloves before using it

23. THANK YOU