Chemistry Reference
In-Depth Information
C16
C6
C11
C6
C1
C2
C15
C12
C4
C3
C13
C14
Cr
Cl
Cl
C8
C7
Cl
Cl
Cl
Cl
Cr(CO)
3
O8
O7
C9
10.155
O9
Figure 10.2
An arene-chromium tricarbonyl complex. Reprinted with permission from Gassman, P. G and
Deck, P. A. Tricarbonyl(
6
-hexachlorobenzene)chromium(0).
Organometallics
1994
,
13
(5), 1934-1939.
C
1994
η
American Chemical Society.
C4
C2
O3
C3
C5
O11
O7
O5
H
O10
C1
O6
N
H
O1
O9
Mn(CO)
3
O3
10.156
Figure 10.3
An indole manganese tricarbonyl complex. Reprinted from
Inorganica Chimica Acta
,
211
,Ryan,
W. J.; Peterson, P. E.
et al.
, “Synthesis and Reactivity of (indole)Mn(CO)
3
complexes. Electrophilic Activation of
the indole 4 and 7 positions, Inorganica Chimica Acta, 211, 1, 1-3.
c
(1993), with permission from Elsevier.
Coordination to the metal has a number of profound effects on the arene (Figure 10.4):
55
the ring becomes
electrophilic and subject to nucleophilic attack,
56
the acidity of the ring protons increases and the acidity of
any benzylic protons also increases. In addition, the formation of benzylic cations is facilitated, as the metal
can stabilize them. Finally, the metal provides huge steric bulk on one face of the arene.
Complexes of heteroarenes are also known.
5
-Pyrrole complexes
10.159
can be prepared, especially using
mild conditions (Scheme 10.40). If more forcing conditions are employed, complexation of a benzene ring is
preferred.
57
The complexes are quite labile and will transfer their chromium unit to another arene readily.
58
Mn(CO)
5
Br
AlCl
3
or AgB
F
4
Cr(CO)
6
,
Δ
R
R
R
R
Mn(CO)
3
Cr(CO)
3
I
2
MeCN,
Δ
1
1
5
1
0
1
Mn(CO)
3
(NCMe)
3
Scheme 10.39
