金属有机13785907

+ PPh2 W PPh2 PPh2 PPh2
H+ direct attack on ligand
PPh2 W PPh2
PPh2
PPh2
initial attack at metal
elimination
PPh2 W PPh2
H
PPh2
+
PPh2
pentagonal bipyramid
Addition to Ligand

Unsaturated ligands: carbon monoxide, isonitriles, olefins, dienes, and arenes do not normally react with nuc- in “free” form (e- rich ligands). Coordination to metal (especially e- deficient metals): ligands push e- density to metal and ligands become e- deficient, “activated,” for nuc- attack. Factors to facilitate nucleophilic attack on unsaturated ligand: a) High reactivity of nucleophiles b) Coordinative saturation of the metal c) Formal positive charge on metal d) -Acceptor “ancillary” ligands
Chapter 8 Nucleophilic and Electrophilic Addition
Types of Reaction
Nucleophiles: Me-, OH-, Et-, CH2CH-,etc. Electrophiles: Me+, H+, Ph3C+, etc. Nucleophilic addition Nucleophilic abstraction Electrophilic addition Electrophilic abstraction
D H Ni
D+
Ni
exo attack
For soft electrophiles, an endo attack is also possible as a result of initial attack of the electrophile at the metal, followed by transfer to the endo face of the ligand.
H
+
CPh3
-Ph3CH Cp(CO)3Mo
+
Cp(CO)2Fe
OH
H+
Cp(CO)2Fe
OH2+
-H2O + Cp(CO)2Feቤተ መጻሕፍቲ ባይዱ
Nucleophilic addition to CO and carbenes
CO
is very sensitive to nucleophilic attack when coordinated to metal sites of low πbasicity. Hydride reagents, organolithium and Grignard reagents, alkoxides, hydroxide, amines, and amide anions.
LnM + MeI electrophilic addition [LnMMe] I
+ -
-L
[L(n-1)MMeI]
H Cp2W H
H
AlMe3
Cp2W H
AlMe3
Addition to a Metal-Ligand Bond Protonation are the most common
ReH(CO)2(PMe2Ph)3 + HBF4 = [Re(H2)(CO)2(PMe2Ph)3]BF4
H Cp2Mo H AlMe3
NEt3
H Cp2Mo H +
Et3N-AlMe3
Electrophilic addition
Cp(CO)2Fe
O O CH2
H
+
Cp(CO)2Fe
Et
+
CH3
Et3O+
Fe(CO)3
Fe+(CO)3
Electrophilic abstraction
Cp(CO)3Mo
OMe Mo(CO)3 + Mo+(CO)3 0oC OMe
-
-15° C
OMe O Mo CO CO C OMe
>0 ° C
H
thermodynamic product
Mo(CO)3
Cyclohexadienyl complexes react with nucleophiles to give 1,3-diene complexes:

Nucleophilic addition
Cl2(py)Pt py Cl2(py)PtR H N
RLi
Cr(CO)3 Cr(CO)3
Nucleophilic abstraction
Cp2TaMe2+ + Me3PCH2
Cp2Ta(=CH2)Me + Me4P+
CH2Na
NaH
Cr(CO)3
Cr(CO)3
H OAc Fe HgOAc Fe HgOAc OAc
Fe
Hg(OAc)2
endo attack
exo-proton abstraction -AcOH
Fe
HgOAc
For a hard electrophile such as CH3CO+, direct exo attack at the ligand tends to be seen, as in acetylation of ferrocene.
H3C D Fe D
CH3CO
+
D D
D D D
O D D D D Fe D
D C Fe D
+
D
exo-proton abstraction
D
COCH3
+
COCH3
-H+
D
Fe D
D H
Inter-ring proton transfer
exo attack
Nu
Ph3C+ Nu-
(OC)3Fe
OMe
OMe Fe+(CO)3
CO2Me O-
OMe Fe(CO)3
( Nu
=
)
Diene complexes give allyls on nucleophilic attack:
(Ind)(CO)2Mo+
H-
(Ind)(CO)2Mo
H3C
Me2N
Fe(CO)2(NO)+
LiNEt2
NEt2 (CO)4Fe C OLi OH+2
Fe(CO)5
MeO3
+
NEt2 (CO)4Fe C OMe OH
Mn(CO)6
+
H2O
(CO)5Mn
C O
-H+
(CO)5Mn
C O
-CO2
(CO)5Mn
H
Nucleophilic addition to polyene and polyenyl ligands
Green-Davies-Mingos Rules:


Polyenes (even or Ln ligands) react before polyenyls (odd or LnX ligands) Open ligands before closed Open polyenes: terminal addition in all cases. Open polyenyls: usually terminal attack, but nonterminal if LnM is electron-donating. Rule 1 takes precedence over rule 2 whenever they conflict.
R* NO Nu-
C5H4
R*
Mo* CO
*Mo+ Nu
NO
CO
*
Electronphilic Addition
An electrophile can attack the ligand, or the M-L bonds, or the metal-even in an 18e complex. AlMe3, BF3, HgCl2, Cu+, etc The mechanism is complex and is less well understood. Addition to the Metal
-H+
Fe(CO)2(NO)
Me2N H
Note that the amine acts as a carbon, not as a nitrogen nucleophile.
η3-Allyls are also readily attacked.
C5H4
R*
+
Mo*
Br NO CO Ag
+
C5H4
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