Chemistry Reference
In-Depth Information
[Al(OC
6
H
2
Bu
t
2
-2,6-Me-4)
2
Me]
561
and [CpAl(OC
6
H
2
Bu
t
2
-2,6-Me-4)
2
],
562
have been
characterized. In the case of mono(aryloxides) a ubiquitous stoichiometry is [(R)
2
M(
2
-
OAr)
2
M(R)
2
](MD Al, Ga, In, Tl) although the metal coordination number varies
from four with simple aryloxides to five for chelating ligands (Tables 6.48 - 6.51). In
the presence of donor ligands, tetrahedral adducts of aluminium aryloxides are very
common,
e.g.
[Al(OC
6
H
3
Pr
i
2
-2,6)
3
(py)],
563
[Al(OC
6
H
2
Bu
t
2
-2,6-Me-4)
2
(H)(OEt
2
)],
557
[Al(OC
6
H
2
Bu
t
2
-2,6-Me-4)Me
2
(NH
3
)],
564
and [Al(OC
6
H
2
Bu
t
3
-2,4,6)Cl
2
(OEt
2
)].
565
With
smaller ligands, five-coordinate species are possible,
e.g.
trigonal bipyramidal
[Al(OC
6
H
3
Pr
i
2
-2,6)
2
(H)(THF)
2
].
566
Particularly important given their intermediacy in
a variety of organic reactions (see above) are adducts formed with ketones and related
carbonyl compounds.
567
6.2.15
Group 14 Metal Aryloxides
The “germylene” and “stannylene” aryloxides [M(OC
6
H
2
Bu
t
2
-2,6-Me-4)
2
](MD Ge,
Sn) can be obtained by treatment of [MfN
SiMe
3
2
g
2
] with phenol.
568
An
intermediate [Sn(OC
6
H
2
Bu
t
2
-2,6-Me-4)fN
SiMe
3
2
g] has been isolated and structurally
characterized.
569
All of these molecules are V-shaped with O-M-O angles of less than
100
Ž
. They will act as two-electron donors to metal fragments,
e.g.
to [Fe(CO)
4
].
570
Addition of N
3
C(O)OAr to [GefN
SiMe
3
2
g
2
] was found to lead to phenoxides such
as [Ge
OPh
CNO
fN
SiMe
3
C
6
H
2
Me
3
g
2
].
571
Tin bis(aryloxides) have also been
reported to be produced by addition of phenols to [(C
5
H
4
Me)
2
Sn]
572
and [Sn(acac)
2
].
573
Aryloxides of Ge(
IV
)andSn(
IV
) can be obtained by reacting the tetrahalides with
LiOAr or reacting [M(NMe
2
)
4
] with phenols.
105
The bonding in these derivatives
(Section 4.2) as well as the sometimes facile activation of arene CH bonds at Sn(
IV
)
metal centres (Section 5.1) has been discussed above. “Hypervalent” anions such as
[Me
3
Sn(OC
6
H
3
Me
2
-2,6)
2
]
have been characterized and their bonding analysed.
574
Although [SnR
4
] compounds do not react with phenols under normal conditions, the
“hypervalently activated” [Me
2
N(CH
2
)
3
SnPh
3
] will undergo stepwise elimination of
benzene and formation of corresponding mono and bis(phenoxides) with phenol.
575
6.2.16
Group 15 Metal Aryloxides
The synthesis of antimony(
III
)
576
,
577
and bismuth(
III
) aryloxides can be achieved by
reacting the trichlorides with either phenols or group 1 metal aryloxides or by treating
trialkyls with phenolic reagents, typically containing electron-withdrawing substituents.
In one case using [NaOC
6
H
2
(CF
3
)
3
-2,4,6] the reaction failed owing to C-F bond activa-
tion by bismuth.
578
The homoleptic [Bi(OC
6
H
3
Me
2
-2,6)
3
]
579
is obtained
via
the chlo-
ride and is a distorted pyramidal monomer (Table 6.56). Dimeric intermediates such as
[Bi
2
(
-OC
6
H
3
Me
2
-2,6)
2
Cl
4
(THF)
2
] have been isolated.
580
The pentafluorophenoxide
(obtained from [BiPh
3
]) is dimeric, with the electrophilic metal centre coordinating
molecules such as toluene and THF.
581
,
582
Further reaction with NaOC
6
F
5
leads to poly-
meric mixed-metal aryloxides.
583
The compound [BiEt
3
] reacts slowly with HOPh and
HOC
6
F
5
to form a mono-aryloxide, which is polymeric in the solid state.
584
Aryloxides
of antimony(
V
) and bismuth(
V
) can be obtained from [MPh
5
] substrates (Tables 6.55
and 6.56). Alternatively the dihalides [X
2
BiPh
3
](XD Cl, Br) can be substituted with
NaOAr reagents.
585
Isolated species such as [Bi(OC
6
F
5
)(Br)Ph
3
] (which undergoes
