Russian Journal of General Chemistry, Vol. 74, No. 1, 2004, p. 141. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 1, 2004, p. 153.
Original Russian Text Copyright
2004 by Rybakova, Tsygankova, Roitershtein, Petrov.
LETTERS
TO THE EDITOR
Metallation of 1,3-Diphenyl-2-benzylpropene
with Diphenylytterbium
L. F. Rybakova, S. V. Tsygankova, D. M. Roitershtein, and E. S. Petrov
Karpov Research Institute of Physical Chemistry, Moscow, Russia
Received January 20, 2003
Metallation of 1,3-diphenyl-2-benzylpropene with
n-butyllithium yields dilithium salt of tribenzylidene-
methane [1, 2]. Several examples of complexes of
early transition metals (Zr, Ta) with tribenzylidene-
methane dianion are known [3, 4], but no attempts to
prepare such complexes with Group II or III elements,
in particular, with rare-earth elements, were made up
to now. In this connection, we examined some routes
to organoytterbium derivatives containing tribenzyl-
idenemethane dianion.
All the reactions involving organolithium and
organolanthanide derivatives were carried out under
dry argon in Schlenk vessels. Organic solvents of pure
grade were refluxed over sodium/benzophenone and
distilled just before the experiment. 1,3-Diphenyl-2-
benzylpropene was prepared as described in [7]. Solu-
tions of YbI2 and organoytterbium compounds (RYbI,
Ph2Yb) were prepared in absolute THF. The metal
was preliminarily activated by the addition of CH2I2
[6, 8, 9].
We found that the complex of ytterbium with tri-
benzylidenemethane dianion formed by the exchange
reaction of YbI2 with tribenzylidenemethane dilithium
salt exhibits low reactivity and does not further react
with 3-methylbenzyl bromide or with organotin or
organogermanium halides.
(PhCHSnPh3)2C=CPh, mp 204 207 C (from
benzene). Found, %: C 69.39; H 4.87; Sn 24.15.
C57H48Sn2. Calculated, %: C 70.92; H 4.89; Sn 24.48.
ACKNOWLEDGMENTS
The study was financially supported by the Russian
Foundation for Basic Research (project no. 01-03-
32838).
Therefore, we attempted metallation of 1,3-di-
phenyl-2-benzylpropene with organic derivatives of
Yb(II) which, as shown by the example of PhYbI and
MeYbI, react with CH and NH acids RH (pKa 18 26)
to form organoytterbium compounds RYbI [5].
Evidently, the CH acidity of 1,3-diphenyl-2-benzyl-
propene is unsufficient for its metallation with both
these reagents. Nevertheless, the desired result is
achieved by the reaction of 1,3-diphenyl-2-benzyl-
propene with diphenylytterbium prepared by the reac-
tion of Yb(0) with Ph2Hg [6]. Two methods of
metallation in THF were tested: addition of Ph2Yb
prepared in advance to a solution of 1,3-diphenyl-2-
benzylpropene and addition of ytterbium metal to a
mixture of 1,3-diphenyl-2-benzylpropene with Ph2Hg
(i.e., use of Ph2Yb generated in situ). After the addi-
tion of triphenyltin chloride to the reaction mixture,
in both cases the distannyl derivative of 1,3-diphenyl-
2-benzylpropene, (PhCHSnPh3)2C=CHPh, was iso-
lated in 40% and 17% yield, respectively. This result,
suggesting transformation of 1,3-diphenyl-2-benzyl-
propene into tribenzylidenemethane dianion under the
action of Ph2Yb, means that organoytterbium(II)
derivatives can be prepared by metallation of CH
acids with diphenylytterbium.
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1070-3632/04/7401-0141 2004 MAIK Nauka/Interperiodica
Rybakova
