Chemistry Reference
In-Depth Information
This process can also lead to the formation of metal - aryloxide bonds
via activation of pendant methoxy-aryl groups. For example the treatment of
[Cp
5
-C
5
H
4
CEt
2
C
6
H
4
OMe-2
TiCl
2
] with LiBr was found to lead to the chelating
phenoxide [Cp
5
-C
5
H
4
CEt
2
C
6
H
4
O-2
TiCl].
114
The use of 2,6-dimethoxyphenyl
substituents can lead to bulky phosphine ligands. Early work by Shaw
et al
. showed
that ligands such as PBu
t
2
fC
6
H
3
OMe
2
-2,6g can generate aryloxy-phosphines with
elimination of MeCl at iridium metal centres.
115
This type of reaction is now been
extended to a variety of metal systems.
116
,
117
In some situations the activation by
metal centres of the stronger aryl-O bond can occur within aryl-ethers.
118
3.4
From Metal Dialkylamides
The homoleptic metal dialkylamides are an important class of compounds in inor-
ganic chemistry.
119
They are typically synthesized by treatment of the corresponding
halide with lithium or sodium dialkylamide. Although involving an extra synthetic
step, there are numerous examples where metal dialkylamide intermediates are useful
in the synthesis of metal aryloxide compounds. The reaction normally involves the
simple addition of the parent phenol to the metal dialkylamide in a nonprotic, typically
hydrocarbon, solvent (Eqs 6.36,
120
6.37,
121
and 6.38
122
).
Ce[N
SiMe
3
2
]
3
C 3HOAr ! Ce
OAr
3
C 3HN
SiMe
3
2
6
.
36
Me
3
C
where
HOAr
=
HO
X;
H, Me, CMe
3
.
X
=
Me
3
C
ArO
Me
2
N
NMe
2
NMe
2
OAr
ArO
6ArOH
(6.37)
Mo
Mo
Mo
Mo
+
6HNMe
2
NMe
2
OAr
Me
2
N
NMe
2
ArO
OAr
H
3
C
where
ArOH
=
HO
.
H
3
C
C4HOAr
!
4HNR
2
[fYb
NR
2
-NR
2
g
2
]
[fYb
OAr
-OAr
g
2
]
6
.
38
Bu
t
where
R
=
SiMe
3
; OAr
=
O
Me
.
Bu
t
The dialkylamine that is produced can be readily removed, leaving the desired
product. In some instances, either incomplete substitution can occur (bulky aryloxides,
