Transcript Notes 07 Organometallic Compounds

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.
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 
Organometallic Compounds
Structure:
Ionic Character: R-M = R- M+
NaR and KR are __________.
Electronegativities:
Na: 0.9, K: 0.8, C: 2.5
CH3F
LiR and MgR have a sigma bond
between the carbon atom and
the metal. These are
________compounds.
Electronegativities:
Li: 1.0, Mg: 1.2
CH3Li
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 –___________
General Mechanisms
1. Nucleophilic Substitution: R2CuLi reaction with
alkyl halides or tosylates.
Nu
C
LG
LG
2. Nucleophilic Addition: RLi or RMgX with
aldehydes or ketones.
O
Nu
Nu
C
C
3. Nucleophilic Acyl Substitution: RLi or RMgX with
esters.
O
O
Nu
Nu
C
LG
C
LG
O
Nu
C
LG
Organolithium Reagents
RX + 2 Li  RLi + Li+X(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:
Organolithium Reagents
RX + 2 Li  RLi + Li+X(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.
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:
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 _____________
Organomagnesium Reagents
Et2O
RX + Mg  RMgX
(X = I, Br, Cl)
Common Reactions with Carbonyl Groups:
Aldehydes/Ketones:
RLi and RMgX react with the carbonyl (C=O) 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.
Organomagnesium Mechanism
RLi
or
RMgX
R
C
H
RLi
or
RMgX
H
O
H
O
R
C
H
R'
RLi
or
O
RMgX
C
R'
C
H
O
H
R
H
H
R'
R'
C
O
H
R
H
R'
R'
R"
C
R"
OH
C
H
R
OH
C
O
H
R
C
R
OH
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.
Grignard Reactions
R’ = Alkyl, vinyl, aryl.
X = Cl, Br, I
R’X
RCHO
H2CO
Mg/Ether
RCOR
HCO2Et
RCN
R’MgX
(EtO)2CO
H2O or acidic H
O
RCO2Et
CO2
Organocopper Reagents
Et2O
2 RLi + CuX  R2CuLi + Li+X(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:
Organocopper Reagents
Et2O
2 RLi + CuX  R2CuLi + Li+X(X = I, Br, Cl)
Limitations:
Organocuprates, R2CuLi, are __________
and can be reacted with _____________________
to give alkanes.
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.
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.
Organozinc Reagents
Synthesis of Cyclopropanes using RZnX
Known as the Simmons-Smith Reaction
Et2O
ICH2I + Zn  I-CH2-ZnI
Cu
Et2O
I-CH2-ZnI + =—R 
+ ZnI2
Iodomethyl zinc iodide is usually prepared using Zn and
activated with Cu.
Iodomethyl zinc iodide reacts with an alkene to give a
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.
CH3
I-CH2ZnI
ZnI2
CH3
Et2 O
I-CH2ZnI
ZnI2
CH3
CH3
Et2 O
Organozinc Reagents
Mechanism of the Simmons-Smith Reaction
+
ZnI2
CH2
I
CH2
ZnI
Reaction is ________________.
Both new C-C bonds are formed simultaneously.
Nucleophilic C=C causes loss of iodide leaving group.
Electrons from nucleophilic C-Zn bond form the other C-C
bond.
Acetylenic Reagents
B:- (B:- = NaNH2)
R—CΞC—H  R—CΞC:- + B-H
Or
B:- (B:- = R’MgX)
R—CΞC—H  R—CΞC:- 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.
Acetylenic Mechanism
RC
CLi
or
RC
CMgX
RC
CLi
or
RC
CMgX
RC
H
C
C
H
H
CLi
R'
O
H
C
H
O
R'
R'
C
C
R'
O
CMgX
H
H
H
or
RC
O
C
H
C
H
H
R'
R'
C
R"
O
O
H
R"
C
OH
OH
OH
R"
C=O in aldehydes/ketones  alcohols.
Addition to methanal (formaldehyde) gives __________________.
Addition to other aldehydes gives ______________________.
Addition to ketones gives tertiary _____________.