Reactivity of triphenylmethyl and triphenylgermyl derivatives of lanthanides

Article abstract of DOI:10.1023/B:RUGC.0000015985.49001.f0

Reactions of bis(triphenylmethyl)ytterbium and bis(triphenylgermyl) ytterbium with mercuric chloride, triphenylbismuth, iodine, tert-butyl alcohol, phenylacetylene, and cyclopentadiene were studied. The higher reactivity of the former compound in these re

Full text of DOI:10.1023/B:RUGC.0000015985.49001.f0

Russian Journal of General Chemistry, Vol. 73, No. 9, 2003, pp. 1395 1397. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 9, 2003,
pp. 1476 1479.
Original Russian Text Copyright
2003 by Zhil’tsov, Makarov, Semkina.
Reactivity of Triphenylmethyl
and Triphenylgermyl Derivatives of Lanthanides
S. F. Zhil’tsov, V. M. Makarov, and N. E. Semkina
Nizhny Novgorod State Pedagogical University, Nizhny Novgorod, Russia
Received December 10, 2001
Abstract Reactions of bis(triphenylmethyl)ytterbium and bis(triphenylgermyl)ytterbium with mercuric
chloride, triphenylbismuth, iodine, tert-butyl alcohol, phenylacetylene, and cyclopentadiene were studied. The
higher reactivity of the former compound in these reactions is explained by that the chemical bond in it is
ionic, whereas in its germyl analog, covalent.
Triphenylmethyl [1] and triphenylgermyl [2] de-
rivatives of lanthanides were synthesized earlier.
X-ray diffraction was used to establish that the
carbon analog [Ph3C]2[Yb(THF)6]2+ has ionic bonds,
whereas the cooresponding germyl compound
(Ph3Ge)2Yb(THF)4 has covalent Ge Yb bonds.
chloride (molar ratio 1:2) by two directions: redox
(3a) and exchange (3b).
2Ph2Yb(THF)2 + HgCl2
a
Ph2YbCl(THF)2 + Hg,
(3)
60%
40%
b
Ph2Hg +YbCl2(THF)2.
30% 40%
Here we turned to previously unexplored reactions
of the above organolanthanides with mercuric chloride,
triphenylbismuth, iodine, and reagents with active
hydrogen atoms (tert-butyl alcohol, phenylacetylene,
and cyclopentadiene CpH).
Evidence for the high reductive activity of bis(tri-
phenylmethy)ytterbium is provided by its reaction
products with triphenylbismuth.
Bis(triphenylmethyl)ytterbium and bis(triphenyl-
germyl)ytterbium react with mercuric chloride in THF
or benzene at room temperature just during reagent
mixing. However, the directions of these prosesses
differ from each other. The first compound acs as a
reducer and is oxidized to bis(triphenylmethyl)ytter-
bium chloride by the stoichiometric reaction equa-
tion (1).
3(Ph3C)2Yb(THF)6 + Ph3Bi
THF
(4)
3(Ph3C)2YbPh(THF)3 + Bi.
70% 90%
20 C
Unlike bis(triphenylmethy)ytterbium, bis(triphenyl-
germyl)ytterbium exhibits no reductive properties
even toward iodine. At equimolar reagent ratio, hexa-
phenylgermanium and ytterbium(II) iodide are formed.
Only when an excess of iodine is present, the resulting
YbI2 is oxidized to form YbI3.
2(Ph3C)2Yb(THF)6 + HgCl2
THF
(1)
2(Ph3C)2YbCl(THF)3 + Hg.
90 95% 90%
The first stage invoves Ge Yb bond fission in the
starting compound.
The covalent analog undergoes an exchange reac-
tion by scheme (2).
THF
(Ph3Ge)2Yb(THF)4 + HgCl2
(Ph3Ge)2Yb(THF)4 + I2
Ph3GeYbI + Ph3GeI. (5)
C6H6
(2)
(Ph3Ge)2Hg + YbCl2(THF)4.
95%
Further mixed compounds undergo symmetrization.
Ph3GeYbI + Ph3GeI Ph3Ge GePh3 + YbI2. (6)
Metallic mercury that might also be formed by
decomposition of bis(triphenylgermyl)mercury was
found only in trace amounts.
The yields of the final products are close to quanti-
tative (90 100%).
It is interesting to note that diphenylytterbium [3]
whose C Yb bond is more covalent in nature than in
the triphenylmethyl derivative reacts with mercuric
Iodine quantitatively oxidizes diphenylytterbium
to an Yb(III) derivative [3].
1070-3632/03/7309-1395$25.00 2003 MAIK Nauka/Interperiodica

1396
ZHIL’TSOV et al.
The IR spectra were obtained on an IKS-25 spec-
THF
2Ph2Yb(THF)2 + I2
2Ph2YbI(THF),
(7)
trometer for samples suspended in mineral oil under
argon. The electronic absorption spectra were obtained
on an SF-16 spectrophotometer. The starting triphenyl-
methyl and triphenylgermyl derivatives of ytterbium
were synthesized according to [1, 2].
20 C, 24h
Bis(triphenylmethyl)ytterbium and bis(triphenyl-
germyl)ytterbium readily react with tert-butyl
alcohol. The former compound begins to react during
reagent mixing at 70 C, and the latter, at 20 C.
Reaction of (Ph3C)2Yb(THF)6 with HgCl2. A
suspension of HgCl2 (0.2219 g) in THF was added to
a solution of (Ph3C)2Yb(THF)6 (1.78 g) in THF
(25 ml), and the mixture was left to stand for 1 h at
20 C. The mixture changed color from bright red to
yellowing brown. Mercury (0.15 g, 92%) was separa-
ted by centrifugation as a dark gray precipitate. The
solvent was removed to isolate 1.41 g (95%) of
(Ph3C)2YbCl(THF)3, mp 195 200 C (decomp.). The
electronic absorption spectrum contains a band at
930 1050 nm, characteristic of Yb3+. Found, %: Cl
3.03; Yb 18.71. C50H54ClO3Yb. Calculated, %: Cl
3.88; Yb 18.98.
(Ph3C)2Yb(THF)6 + 2t-BuOH
THF
t-(BuO)2Yb + 2Ph3CH,
71% 100%
(8)
(9)
(Ph3Ge)2Yb(THF)4 + 2t-BuOH
THF
t-(BuO)2Yb + 2Ph3GeH.
88% 72%
The above reactions give rise to ytterbium(II) tert-
butoxide. The product is blue in color, it is insoluble
in THF, benzene, and hexane, and melts at 300 C
with decomposition.
Reaction of (Ph3C)2Yb(THF)6 with Ph3Bi. A
solution of Ph3Bi (0.15 g) in THF was added to a
solution of (Ph3C)2Yb(THF)6 (1.14 g) in 25 ml of
THF. The mixture was heated at 40 50 C for 24 h.
Therewith, it changed color from bright red to dark
red, and a dark gray precipitate (bismuth) formed,
which was separated by centrifugation (0.065 g, 90%).
From the solution, 0.676 g (68%) of (Ph3C)2YbPh
(THF)3 was isolated. mp 75 80 C (decomp.). The
electronic absorption spectrum contains bands at 430
465 and 950 1000 nm due to [Ph3C] and Yb3+,
respectively. Found Yb, %: 18.07. C56H59O3Yb.
Calculated Yb, %: 18.18.
Since (triphenylmethyl)ytterbium proved to be very
active in the reactions studied, we brought it into re-
action with other reagents having active hydrogen:
phenylacetylene and cyclopentadiene CpH. As the
reagents were mixed in THF at 70 C, the solution
changed color. The reaction mixture was allowed to
warm to room temperature and analyzed.
(Ph3C)2Yb(THF)6 + 2PhC CH
THF
(PhC C)2Yb(THF)2 + 2Ph3CH,
76% 87%
(10)
(11)
Reaction of (Ph3C)2Yb(THF)6 with t-BuOH. tert-
Butyl alcohol (0.048 g) was added to a solution of
(Ph3C)2Yb(THF)6 (0.355 g) in THF, cooled to 70 C.
The reaction mixture was slowly heated to room
temperature. A bluish precipitate formed in the light
yellow solution and was washed with THF (7 10 ml)
and dried in a vacuum to obtain 0.07 g (68%) of
ytterbium bis(tert-butoxide) [4] as a blue material, mp
300 C. Found Yb, %: 54.14. C8H18O2Yb. Calculated
Yb, %: 54.20. From the THF solution, 0.16 g (100%)
of Ph3CH was isolated, mp 93 95 C (mixed sample).
(Ph3C)2Yb(THF)6 + 2CpH
THF
Cp2Yb(THF) + 2Ph3CH.
57%
80%
These reactions can be used to synthesize phenyl-
ethynyl and cyclopentadienyl lanthanide derivatives
in fairly high yields.
Thus, we showed that bis(triphenylgermyl)ytter-
bium and bis(triphenylmethyl)ytterbium are highly ac-
tive in the reactions studied, which suggests wide use
of such reactions in organic and organometallic syn-
thesis. Moreover, we found that the direction of some
of the reactions studied is much dependent on the na-
ture of chemical bond in the organolathanide reagent.
Reaction of (Ph3C)2Yb(THF)6 with PhC CH.
Crystalline (Ph3C)2Yb(THF)6 (1.4 g) was dissolved
in THF. The solution was cooled with a mixture of
acetone in liquid nitrogen to 70 C, and PhC CH
(0.27 g) of THF was added to it. As the reagents were
mixed, the mixture changed color from bright red to
dark brown. It was slowly heated to room temperature.
The solvent was removed in a vacuum, and the re-
sidue was washed with hexane (10 10 ml) and dried
in a vacuum to obtain 0.51 g (77%) of (PhC C)2
EXPERIMENTAL
All operations were performed in evacuated sealed
ampules using thoroughly dried and degassed solvents.
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REACTIVITY OF TRIPHENYLMETHYL
1397
Yb(THF)2 as a black material. mp > 250 C (decomp.).
Found Yb, %: 33.42. C24H26O2Yb. Calculated Yb, %:
33.31. From the hexane extracts, 0.55 g (88%) of
Ph3CH was isolated, mp 93 95 C.
hydrofuran-soluble products were studied by elec-
tronic spectroscopy at 600 1100 nm. The lack of a
band at 900 1000 nm provides evidence showing that
the ytterbium atom has not been oxidized to the tri-
valent state.
Reaction of (Ph3C)2Yb(THF)6 with CpH.
(Ph3C)2Yb(THF)6 (0.39 g) was dissolved in THF. The
solution was cooled with a mixture of acetone and
liquid nitrogen to 70 C, and a solution of CpH
(0.05 g) in THF was added to it. As the reagents were
mixed, the mixture changed color from red to reddish
violet. It was slowly heated to room temperature, the
solvent was removed in a vacuum. Therewith, the
products changed color to bright yellow. The contents
of the ampule was washed with hexane (7 10 ml).
A product insoluble in hexane was dried in a
vacuum to obtain 0.08 g (56%) of Cp2Yb(THF). mp
250 C (decomp.). Found Yb, %: 40.21. C14H18OYb.
Calculated Yb, %: 40.33. From the hexane extracts,
0.14 g (80%) of Ph3CH was isolated, mp 91 93 C.
A new portion of I2 (0.08 g) in 5 ml of THF was
added to the soluble products [unreacted bis(tri-
phenylgermyl)ytterbium]. The solution got almost
colorless, and a red precipitate formed. From the
precipitate, hexaphenyldigermanium and ytterbium(II)
iodode were isolated in yields of 100 (0.07 g) and
88% (0.22 g) with respect to the starting organoger-
manium compound.
Reaction of (Ph3Ge)2Yb(THF)4 with t-BuOH.
tert-Butyl alcohol (0.16 g) was added to a solution of
(Ph3Ge)2Yb(THF)4 (0.56 g) in 20 ml of THF. A dark
blue precipitate immediately formed over the whole
volume. The reaction mixture was left to stand at
room temperature for 2 h, and the solution was de-
canted. The precipitate was washed with hexane (3
10 ml). From the hexane solution, 0.23 g (72%) of
triphenylgermane was isolated, mp 42 C (mixed
sample). The hexane-insoluble amorphous blue
material (0.15 g, 88%), decomp. point 300 C, was
found to be (t-BuO)2Yb. Found Yb, %: 53.18.
C8H18O2Yb. Calculated Yb, %: 54.20.
Reaction of (Ph3Ge)2Yb(THF)4 with HgCl2. A
solution of (Ph3Ge)2Yb(THF)4 (0.29 g) in 15 ml of
C6H6 was added to a suspension of 0.07 g of HgCl2
in 10 ml of benzene. The reaction occurred as the
regents were mixed. The solution changed color from
yellow to light gray. After standing, a light gray
precipitate formed. The benzene solution was de-
canted, and the precipitate was dried in a vacuum and
analyzed in air. Treatment of the precipitate with
concentrated ammonia gave no black coloration,
implying lack of mercurous chloride. The precipitate
that was found to be ytterbium chloride (0.06 g, 64%)
was dissolved in 0.02 N HCl. The solution was de-
canted to leave on the bottom of the ampule traces of
metallic mercury. The benzene solution was eva-
porated in a vacuum. The dry residue was bis(tri-
phenylgermyl)mercury (0.19 g, 94%), decomp. point
213 215 C. Found Hg, %: 24.11. C36H30Ge2Hg.
Calculated Hg, %: 24.83.
ACKNOWLEDGMENTS
The work was financially supported by the
Ministry of Education of the Russian Federation
(common order for 2000 2003).
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