SCHEDULED MAINTENANCE
Synthesis, multinuclear magnetic resonance spectroscopic studies and crystal structures of mono- and di-selenoether complexes of tin(IV) halides
Abstract
Reaction of SnX
4
(X = Cl or Br) with
Me
2
Se or diselenoether ligands in dry CHCl
3
produced white or yellow solids [SnX
4
L
2
] in high
yield [X = Cl,
L
2
= MeSe(CH
2
)
n
SeMe, PhSe(CH
2
)
n
SePh
(n = 2 or 3),
C
6
H
4
(SeMe)
2
-o or
2Me
2
Se; X = Br,
L
2
= MeSe(CH
2
)
n
SeMe (n = 2 or 3),
C
6
H
4
(SeMe)
2
-o or
2Me
2
Se]. These compounds have been characterised by a
combination of variable-temperature
1
H,
119
Sn-{
1
H} and
77
Se-{
1
H} NMR, IR spectroscopy and
microanalyses. Single-crystal X-ray diffraction studies on
trans-[SnX
4
(SeMe
2
)
2
],
[SnX
4
{C
6
H
4
(SeMe)
2
-
o}] (X = Cl or Br) and
[SnCl
4
{MeSe(CH
2
)
3
SeMe}]
confirm distorted octahedral geometry at Sn
IV
in each case,
with the bidentate ligands chelating. The
C
6
H
4
(SeMe)
2
-o complexes adopt
the meso arrangement, while the ligand is in the DL
form in
[SnCl
4
{MeSe(CH
2
)
3
SeMe}]. The
trends in d(Sn–X) and d(Sn–Se) reveal
that the trans influence of halide is greater than that of
selenium in these systems. In comparable systems
d(Sn–Se) is longer in the bromo than in the chloro
systems, consistent with the greater Lewis acidity of SnCl
4
.
The NMR studies revealed that pyramidal-inversion and
ligand-dissociation processes are facile. In the SeMe
2
complexes both cis and trans isomers are present,
while in the diselenoether systems the meso and DL
forms are both apparent at low temperatures. The co-ordination shifts in
the
77
Se-{
1
H} NMR spectra are markedly
dependent upon chelate-ring size; the first time this has been observed
for complexes of a p-block metal.
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