Sections 6.1-6.3

1
Organometallics
2
Organometallic Compounds

• Compounds that contain _________________bond
  (______)
• Examples of M include ________(Grignard
  reagents), _____________.
• ____________ carbon Reacts with _____________
  carbon and forms a new _________________.
• Nomenclature Similar naming to substituted
  metals (alkyl metals or alkyl metal halides).
• Organomagnesium Grignard reagent.
• CH3Li Methyl lithium.
• CH3MgBr Methyl MgBr.

3
Organometallic Compounds

• Properties
• High Reactivity Organmometallics are usually
  kept in organic solvents due to their very high
  reactivity.
• Reacts especially with H2O, O2, etc.
• RMgX H2O ?
• RMgX O2 ?

4
Organometallic Compounds

• Structure
• Ionic Character R-M R- M
• NaR and KR are __________.
• Electronegativities
• Na 0.9, K 0.8, C 2.5
• LiR and MgR have a sigma bond between the carbon
  atom and the metal. These are ________compounds.
• Electronegativities
• Li 1.0, Mg 1.2

5
Organometallic Compounds

• Reactivity Bases act as ___________
• Basicity
• Simple carbanions are _____________.
• Carbon is not very electronegative compared to
  nitrogen or oxygen.
• RLi HOR ? _________
• RMgX HOR ? ______________
• RLi or RMgX _________ be used in the presence
• of _____________, such as ___________

6
General Mechanisms

• Nucleophilic Substitution R2CuLi reaction with
  alkyl halides or tosylates.
• Nucleophilic Addition RLi or RMgX with aldehydes
  or ketones.
• Nucleophilic Acyl Substitution RLi or RMgX with
  esters.

N
u
C
L
G
7
Organolithium Reagents
RX 2 Li ? RLi LiX- (X I, Br, Cl)

• Reaction Type
• Alkyl halides react with lithium metal.
• Other Group I metals (Na, K) can be used instead
  of lithium.
• Solvents
• Alkyl group can be.
• R can be.
• Halide Reactivity

8
Organolithium Reagents
RX 2 Li ? RLi LiX- (X I, Br, Cl)

• Limitations
• Organolithium, RLi, is _____________for an SN1
  or SN2 with alkyl halides or tosylates.
• This gives __________________ reaction or other
  side reactions.

9
Organomagnesium Reagents
Et2O RX Mg ? RMgX (X I, Br, Cl)

• Reaction Type
• Alkyl halides react with magnesium metal.
• Solvents
• Alkyl group can be primary, secondary or
  tertiary.
• R can be alkyl, vinyl or aryl.
• Halide Reactivity

10
Organomagnesium Reagents
Et2O RX Mg ? RMgX (X I, Br, Cl)

• Limitations
• Organomagnesium, RMgX is ___________for SN1 or
  SN2 with alkyl halides or tosylates. In these
  situations, RMgX gives ___________ reactions and
  other side reactions.
• Common Reactions with Carbonyl Groups
• Aldehydes/Ketones
• RLi and RMgX react with the _____________

11
Organomagnesium Reagents
Et2O RX Mg ? RMgX (X I, Br, Cl)

• Common Reactions with Carbonyl Groups
• Aldehydes/Ketones
• RLi and RMgX react with the carbonyl (CO) to
  create _____________.
• Addition to methanal (formaldehyde) ?
  __________.
• Addition to other aldehydes ? ______________.
• Addition to ketones ? ____________.
• The acidic work-up intermediate metal
  alkoxide salt ? alcohol via a simple _________
  reaction.

12
Organomagnesium Mechanism
R
L
i
O
o
r
C
R
M
g
X
H
H
R
L
i
O
o
r
C
R
M
g
X
R
'
H
R
L
i
O
o
r
C
R
M
g
X
R
"
R
'
13
Esters

• Reaction Type
• Requires ________ equivalents of organolithium or
  Grignard reagents.
• Product _______________
• Tertiary alcohol contains ______________ alkyl
  groups via a _____________which reacts with the
  second equivalent of the organometallic.
• Since the ketone is ________________ than the
• ester, the reaction _______ stop at a
  ketone.

14
Grignard Reactions
R Alkyl, vinyl, aryl. X Cl, Br, I
RX
RCHO
H2CO
RCOR
HCO2Et
RCN
RMgX
(EtO)2CO
H2O or acidic H
CO2
RCO2Et
15
Organocopper Reagents
Et2O 2 RLi CuX ? R2CuLi LiX- (X I, Br,
Cl)

• Lithium Dialkylcuprates, R2CuLi
• _____ organolithiums with a copper (I) halide.
• Solvents
• The alkyl group is usually ____________.
  _____________are prone to decomposition.
• R can be _________________________.
• Halide Reactivity

16
Organocopper Reagents
Et2O 2 RLi CuX ? R2CuLi LiX- (X I, Br,
Cl)

• Limitations
• Organocuprates, R2CuLi, are __________
• and can be reacted with _____________________ to
  give alkanes.

17
Organocopper Reagents

• Alkane Synthesis Using R2CuLi
• R2CuLi R-X ? R-R RCu LiX
• Reaction Type
• Creation of new C-C bonds.
• ______________are best, otherwise an elimination
  reaction can occur.
• The R group in the halide can be ______________
• The R group of the cuprate can be ______________
• Although the mechanism looks like a _________
  reaction, it is more complex and is not well
  understood.

18
Organozinc Reagents
Et2O RX Zn ? RZnX (X I, Br, Cl)

• Reaction Type
• RZnX is made in a similar fashion as
• RZnX is _________ reactive than RLi or RMgX with
  aldehydes and ketones.
• The most common application of organozinc
  reagents is in the Simmons-Smith Reaction.

19
Organozinc Reagents

• Synthesis of Cyclopropanes using RZnX
• Known as the Simmons-Smith Reaction
• Iodomethyl zinc iodide is usually prepared using
  Zn and activated with Cu.
• Iodomethyl zinc iodide reacts with an alkene to
  give a

Et2O ICH2I Zn ? I-CH2-ZnI Cu
Et2O I-CH2-ZnI R ?
ZnI2
20
Organozinc Reagents

• Synthesis of Cyclopropanes using RZnX
• Reaction is __________specific with respect to
  the alkene.
• Mechanism is ____________.
• Substituents that are _______ in the alkene are
  ______ in the cyclopropane.
• Substituents that are______ in the alkene are
  ______ in the cyclopropane.

21
Organozinc Reagents

• Mechanism of the Simmons-Smith Reaction
• Reaction is ________________.
• Both new C-C bonds are formed simultaneously.
• Nucleophilic CC causes loss of iodide leaving
  group.
• Electrons from nucleophilic C-Zn bond form the
  other C-C bond.

C
H
I
Z
n
I
2
22
Acetylenic Reagents
B- (B- NaNH2) RC?CH ? RC?C-
B-H Or B- (B- RMgX) RC?CH ?
RC?C- MgX R-H

• Reaction Type
• Reacts as a _______________
• 3 important groups of reactions where
  nucleophiles attack electrophilic C atoms.
• Product is new C-C bonds.

23
Acetylenic Mechanism
C
L
i
R
C
O
o
r
C
C
M
g
X
R
C
H
H
CO in aldehydes/ketones ? alcohols. Addition to
methanal (formaldehyde) gives __________________.
Addition to other aldehydes gives
______________________. Addition to ketones gives
tertiary _____________.