Chemistry Reference
In-Depth Information
Table 6.17
Strontium aryloxides
Bond
Bond
length ( A)
angle (
Ž
)
Compound
Aryloxide
M-O
M-O-Ar
Ref.
[Sr
4
OAr
8
HOAr
2
THF
6
]
OC
6
H
5
2.450 (7)
i
6-coord. Sr
2
-OC
6
H
5
2.404 (7) - 2.495 (7)
3
-OC
6
H
5
2.512 (7) - 2.558 (6)
OC
6
H
2
Bu
t
3
-2,4,6
[Sr(OAr)
2
THF
3
]
2.306 (5)
175
ii
tbp, equatorial OAr
2.323 (5)
176
[Sr
3
OAr
6
HMPA
5
]
OC
6
H
5
2.34 (3)
169
iii
2
-OC
6
H
5
2.38 (3) - 2.53 (2)
3
-OC
6
H
5
2.52 (2) - 2.65 (2)
[Ba
2
Sr
6
OAr
14
O
2
H
2
HMPA
6
]
2
-OC
6
H
5
2.52 (3) - 2.62 (4)
iv
two fused Sr
3
Ba
2
square
3
-OC
6
H
5
2.44 (3) - 2.71 (3)
pyramids with
5
-O, 6-coord.
Sr and 6- and 8-coord. Ba
[Sr(OAr)
2
]
.
5H
2
O
2
-OC
6
H
2
NO
2
3
-
2.604 (4), 2.843 (4)
v
8-coord. Sr, polymeric structure
2,4,6
i
S.R. Drake, W.E. Streib, M.H. Chisholm, and K.G. Caulton,
Inorg. Chem.
,
29
, 2707 (1990).
ii
S.R. Drake, D.J. Otway, M.B. Hursthouse, and K.M.A. Malik,
Polyhedron
,
11
, 1995 (1992).
iii
K.G. Caulton, M.H. Chisholm, S.R. Drake, K. Folting, J.C. Huffman, and W.E. Streib,
Inorg.
Chem.
,
32
, 1970 (1993).
iv
K.G. Caulton, M.H. Chisholm, S.R. Drake, K. Folting, and J.C. Huffman,
Inorg. Chem.
,
32
,
816 (1993).
v
J.M. Harrowfield, B.W. Skelton, and A.H. White,
Aust. J. Chem.
,
48
, 1311 (1995).
6.2.3
Group 3 Metal and Lanthanide Aryloxides
The synthesis of group 3 metal and lanthanide aryloxides can be achieved utilizing
metal halide substrates reacted with alkali metal aryloxides. Homoleptic, base-
free metal(
III
) aryloxides can be formed by this method when the aryloxide is
bulky,
e.g.
[Sc(OC
6
H
2
Bu
t
2
-2,6-Me-4)
3
],
289
[M(OC
6
H
3
Bu
t
2
-2,6)
3
](MD La, Sm),
290
and
[Ce(OC
6
H
3
Bu
t
2
-2,6)
3
]
291
(which is also obtained via [CefN
SiMe
3
2
g
3
].
292
However, in
a number of homoleptic derivatives there exists association via
-interaction with the
phenoxide nucleus and adjacent metal centres,
e.g.
[(ArO)
2
M(
2
-O-
6
-OAr)
2
M(OAr)
2
]
(M D La, Sm, Nd; ArO D OC
6
H
3
Pr
i
2
-2,6) (Table 6.19).
293
The reaction of substrates
such as [SmfCH
SiMe
3
2
g
3
] (itself prepared from a homoleptic aryloxide) [Cp
3
Ln]
(Ln D Nd, Yb),
91
[Cp
2
Sm(thf)
2
],
294
and [ScfN
SiMe
3
2
g
2
THF
3
] with phenols has
been shown to yield corresponding metal(
II
)and(
III
) aryloxides.
295
An important
alternative synthetic strategy involves reaction of the lanthanide metal itself with the
phenol. This can occur in the presence of aryl-mercury reagents (Eq. 6.12).
296
,
297
Direct
reaction of europium
298
and ytterbium
299
with 2,6-dialkylphenols in liquid ammonia
has been reported. Recently
N
-methylimidazole and acetonitrile have been shown to
be suitable solvents for the production of europium aryloxides from the metal.
300
The
conversion of ytterbium(
III
) aryloxides to the corresponding bis-aryloxide has been
achieved using Yb metal as the reducing agent.
In the case of 2,6-diphenylphenoxide ancillary ligands, chelation to the electron-
deficient metal via
-interactions with
ortho
-phenyl rings has been observed in a large
number of cases (Table 6.19). In some compounds only a fraction of the arene ring
