Chemistry Reference
In-Depth Information
similar, with the difference that lone pair sites on sodium are occupied by benzene
ligands along with the presence of four instead of six doubly bridged fluoroalkoxo
groups. These crystallographic studies have also indicated evidence of secondary
heterometal (Tl or Na)
...
F interactions.
227
In view of the highly interesting findings
with fZr
2
OPr
i
9
g
ligands, it would be worthwhile to investigate the ligating behaviour
of the fluorinated analogue, fZr
2
OR
f
9
g
further.
The derivatives [f
COD
Rhg
2
fSn
OEt
6
g]
229
and [f
COD
Phg
2
fTi
OPr
n
6
g]
230
are
also similar, with the difference that the two terminally bonded M-O-C groups on
titanium are almost linear (160
Ž
), whereas they are more bent (125
.
5
Ž
) in the case of
tin; the acute bond angle appears to be a general feature in main-group metal chemistry.
The structure of [f
dme
Nag
2
Ce
3
-OBu
t
-OBu
t
3
OBu
t
2
]
228
is interesting in
that
dme
2
Na
C
electrophiles occupy adjacent rather than
trans
-faces, which would
have given a more linear Na/Ce/Na geometry. By contrast, Tl
2
Sn
OEt
6
55
exists as a
one-dimensional polymer in the solid state, owing to the lone pair electrons on thallium.
3.5
Heterometallic Alkoxides with Other Chelating Ligands
Previous sections have dealt with heterobimetallic alkoxides with the four most
commonly used ligands: fAl
OR
4
g
, fNb
OR
6
g
, fTa
OR
6
g
, and various types
of alkoxometallates(
IV
). A brief description is presented in this section of a few
alkoxometallate(
II
) and other ligands.
A detailed study has been made in the research school of Veith
54
on a variety of
derivatives with fM
OBu
t
3
g
type ligands (M D a divalent metal like Ge, Sn, and
Pb), involving reactions of the following types.
M
0
OBu
t
C M
OBu
t
2
!
1
n
fM
0
M
OBu
t
3
g
n
3
.
125
where M D Ge, Sn, Pb; M
0
D Li, Na, K, Rb, Cs.
2M
0
Br C Na
2
M
2
OBu
t
6
! 2[M
0
M
OBu
t
3
] C 2NaBr
3
.
126
where M D Ge, Sn, Pb; M
0
D In, Tl.
M
0
Cl
2
C Na
2
M
2
OBu
t
6
! MM
0
2
OBu
t
6
C 2NaCl
3
.
127
where M
0
D Mg, Mn, Zn and M D Ge or M
0
D Mn, Zn and M D Pb.
These are interesting “cage” compounds.
Another type of compound (3-IV) has also been obtained,
54
,
163
,
231
with the formula
[M
0
2
M
2
OBu
t
8
](MD Ge, Sn, Pb; M
0
D Mg, Ni, Cr, Co, Mn).
O
O
O
OR
M
M
′
M
′
M
•
•
R
R
R
OR
(3-IV)
