1. Organometallic 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+)
Organocopper - Cu (C--Cu+)

5. Organomagnesium Compounds
Grignard Reagents
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
Mg, Et2O

6. Reactivity of Alkyl Halides
R-I > R-Br > R-Cl
Preparation of Grignards from: primary, secondary & tertiary alkyl halides.
Grignard formation from aryl halides and allyl halides; however these may give Wurtz type coupling products.
I2 maybe used to speed-up the formation Grignard reagents from alkyl bromides or chlorides

7. Organolithium Compounds
Alkyl Lithium Compounds
Methyllithium – CH3Li
Ethyllithium - CH3CH2Li
Draw the structures of these Alkyl lithium compounds
n-propyllithium
tert-butyllithium
Preparation of organolithium reagents:
CH3-Br CH3Li + LiBr
2 eq. Li, Et2O

8. Organocopper Compounds
Lithium Dialkylcopper (organocuprate ) [(R)2Cu]- Li+
Cuprates are less reactive than organolithium
R acts as a Nucleophile
Oxidation state of copper is Cu(I).
Nucleophile “R” will attack various organic electrophiles.
Organocuprates are used in cross-coupling reactions to form higher alkanes.
Cross-Coupling Reaction: coupling of two different alkyls R and R’ to yield a new alkane (R-R’). This type of reaction is used to make new C-C between alkyl groups.

9. Organocuprates Preparation of organocuprates:
2 CH3Li [(CH3)2Cu]- Li+ + LiI
As a reagent for Organic Synthesis:
[(CH3)2Cu]- Li CH3CH2CH2I CH3CH2CH2CH3
Formation of new C-C bonds
The electrophile CH3CH2CH2I (R-X) must be a 1 alkyl halide for a good product yield.
CuI, Et2O
-RCu, -LiI

10. Organic Synthesis Give a stepwise synthesis for Isobutane.
2,2-dimethylheptane