II
II
Redox reactions of Ge and Sn dihalides
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 7, July, 2002
1327
1
9
20
this reaction (as exemplified by the reaction of Et SiH
Oxidation of triethylsilane , triethylgermane, and
3
2
1
with GeCl •dioxane) can be proposed:
triethylstannane under the action of such efficient oxiꢀ
2
dizing agents as transition metal salts MX was described
n
in the literature. In all cases, Et EX (E = Si, Ge, or Sn)
3
were formed and the salts were reduced to MXn–m
(
n – m = 1 or 2) or free metal M.
To summarize dihalogermylenes (dihalostannylenes)
and their complexes, unlike organylgermylenes, were not
inserted at the Si—H and Ge—H bonds. The reactions
of SnI , ECl •dioxane, and (CO) W=ECl •THF (E =
2
2
5
2
Ge or Sn) with Et E´H (E´ = Si or Ge) occur as reꢀ
3
dox processes to form the products of oxidative coupling
(
Et SiSiEt ) and/or haloiodination (Et SiX or Et GeX)
3 3 3 3
of triethylsilane (triethylgermane) depending on the naꢀ
ture of the reagents.
•
+
It should be noted that the existence of the (Et SiH)
3
radical cation17 and (GeCl •dioxane) radical anion
•–
14
2
has been proved previously.
Experimental
In principle, the formation of Et SiSiEt may also be
3
3
associated with the bimolecular S 2 reaction of the
H
1
The H NMR spectra were recorded on a Bruker AC 200
triethylsilyl radical with the starting silane analogously
instrument (200 MHz). The GLCꢀmass spectra (EI, 70 eV)
were measured on a Finnigan MAT INCOS instrument
•
to that observed in the interactions of Et Si with dialkyl
3
sulfides, dialkyl selenides, and bis(trimethylsilyl)merꢀ
cury.18 The possibility of the formation of the Si—Si
bond via the direct attack of the triethylsilane radical
cation on the starting silane must not be ruled out as
well. It is this reaction that is the key step in the mechaꢀ
nism of electrochemical polymerization of diorganylꢀ
silanes.1
(
RSLꢀ200 column, 30 m × 0.25 mm). The solvents used in the
reactions were dried over molecular sieves (CD CN) or soꢀ
dium metal (C D ). The GeCl •dioxane, SnCl •dioxane,
(
plexes as well as GeI2 and SnI2 were prepared according to
known procedures.
3
2
2
23
6
6
2
2
2
4
25
CO) W=GeCl •THF, and (CO) W=SnCl •THF comꢀ
5 2 5 2
2
6
26
General procedure for the reactions. The EX2 compound
6
(
EX2 = ECl •dioxane, EI , or (CO) W=ECl •THF, where
2 2 5 2
Other experimental facts can also be explained asꢀ
E = Ge or Sn) (0.661 mmol) was added to a solution of Et E´H
(E´ = Si or Ge) (0.661 mmol) in CD CN (C D ) (0.5 mL) in
an NMR tube under Ar. The course of the reactions was moniꢀ
tored by H NMR spectroscopy (from the disappearance of the
3
suming that the reactions of Et E´ with ECl •dioxane
3
2
3
6
6
and (CO) W=ECl •THF (E = Ge or Sn) involve the
5
2
1
oneꢀelectron transfer. Thus, Et E´H (E´ = Si or Ge) did
3
not react with GeI due, apparently, to the fact that the
reduction potential of this germylene is in a much higher
signal for the Si—H group (δ 3.63) in Et SiH and Ge—H group
2
3
1
(
δ 3.69) in Et GeH). H NMR for Et SiSiEt3 (CD CN), δ:
3
3
3
0
.55 (m, 4 H, CH —Si); 1.00 (m, 6 H, CH ). The reaction
cathodic region as compared to the reduction potenꢀ
2
3
red
mixture was analyzed by GLCꢀmass spectrometry.
tial of GeCl •dioxane (E
(GeI ) = –0.99 V and
2
1/2
2
red
E1/2 (GeCl •dioxane) = –0.41 V with respect to
2
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos. 00ꢀ15ꢀ97387
and 99ꢀ03ꢀ32885), by INTAS (Grant 97ꢀ30344), and by
the Ministry of Industry, Science, and Technology of
the Russian Federation and the Russian Academy of
Sciences (Project 1ꢀ20).
1
3
Ag/AgCl/KCl (saturated) ).
The absence of Et GeGeEt among the products of
3
3
the reactions of Et GeH with ECl •dioxane, SnI , and
3
2
2
(
CO) W=ECl •THF (E = Ge or Sn) can be attribtued
5 2
to the fact that the fragmentation of the initially formed
•+
Et GeH radical cation follows another pathway.
3
References
1
. J. Satgé, M. Massol, and P. Riviere, J. Organomet. Chem.,
973, 56, 1.
1
2
3
4
. J. Satgé, Pure Appl. Chem., 1984, 56, 137.
. W. P. Neumann, Chem. Rev., 1991, 91, 311.
. E. P. Mayer, H. Nöth, W. Rattay, and U. Wietelmann,
Chem. Ber., 1992, 125, 401.
5
. S. Konieczny, S. J. Jacobs, W. J. K. Bradock, and P. P.
Gaspar, J. Organomet Chem., 1988, 341, 17
EX2 = ECl •dioxane, SnI , (CO) W=ECl •THF (E = Ge, Sn)
6. K. Mochida and A. Nasegava, Chem. Lett., 1989, 1087.
2
2
5
2