Reaction of Ytterbium(II) and Praseodymium(III) phenylethynyl cuprates with trimethylsilyl iodide

Full text of DOI:10.1134/S1070363212030231

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 3, pp. 504–505. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © N.A. Pimanova, M.A. Dydykina, O.N. Druzhkova, S.F. Zhyl’tsov, 2012, published in Zhurnal Obshchei Khimii, 2012, Vol. 82, No. 3,
pp. 511–513.
LETTERS
TO THE EDITOR
Reaction of Ytterbium(II) and Praseodymium(III)
Phenylethynyl Cuprates with Trimethylsilyl Iodide
N. A. Pimanova, M. A. Dydykina, O. N. Druzhkova, and S. F. Zhyl’tsov
Nizhny Novgorod State Pedagogical University, ul. Ul’yanova 1, Nizhny Novgorod, 603950 Russia
e-mail: chemical@nnspu.ru
Received June 21, 2011
DOI: 10.1134/S1070363212030231
{[(PhC≡C)3Cu]Yb(THF)2}2 + Me3SiI → PhC≡CCu
+ Me3SiC≡CPh + PhC≡CYbI(THF)3 + YbI2(THF)3.
We have developed preparative methods for phenyl-
ethynyl lanthanide cuprates [1] which make them
available as an object of study. Like lithium
organocuprates, which are highly selective alkylating
and arylating agents, they can be used in organic and
organometallic syntheses. It has been shown [2] that
praseodymium and ytterbium phenylethynyl cuprates
react peculiarly with acyl halides to give poly-
functional organic and organometallic compounds.
Therefore it was interesting to study their reactivity
toward trimethylsilyl halides.
Like in the case of praseodymium(III) organo-
cuprate, similar ytterbium(II) complex eliminates phenyl-
ethynylcopper and undergoes a stepwise dealkynyla-
tion to form the cross-coupling product (trimethylsilyl
phenylacetylenide) and a mixture of the above
ytterbium(II) iodides. The reaction mixture contains
phenylacetylene (5–10%) due likely to the generation
of phenylethynyl radicals as a result of a side process
involving the act of one-electron transfer, noted earlier
[3] in the reaction of lanthanide compounds with
phenylethynyl halides R3EX (E = Si , Ge, Sn; X = Cl,
I; R = alkyl, phenyl).
Praseodymium(III)
phenyethynyl
cuprate
[(PhC≡C)3Cu]3Pr2(THF)6 reacts with trimethylsilyl
iodide in a 1:6 ratio in THF solution at room
temperature. The reaction is accompanied by the
formation of a yellow precipitate of phenylethynyl-
copper and phenylethynyltrimethylsilicon. Prolonged
(up to 10 days) standing of the reaction mixture
resulted mainly in phenylethynylpreseodymium di-
iodide coordinated with THF.
The ytterbium(II) and praseodymium(III) phenyl-
ethynyl cuprate complexes are inferior to the
corresponding homoleptic lanthanide compounds [4]
in the reactivity with respect to trimethylsilyl iodide,
but the reaction of al these compounds occurs under
mild conditions in the absence of a catalyst.
The IR spectra were recorded on a FSM 1201 FT-
IR spectrometer. The samples of these unstable in air
compounds were prepared in a vacuum or in an argon
atmosphere as suspensions in mineral oil. The NMR
spectra were registered on a spectrometer Bruker
DPX-200 (1H at 200 MHz, 13C at 50 MHz). The
chemical shifts are given in parts per million (ppm)
relative to tetramethylsilane as an internal reference.
The chromatographic analysis of volatile compounds
was carried out on a Tsvet-100 chromatograph
equipped with katharometer [column 100×0.3 cm,
200×0.3 cm filled with PEG-1500 (20%) on Chesasorb
AW-HMDS], carrier gas helium. The melting and
decomposition points were determined in evacuated
sealed capillaries. The melting and decomposition
points were not corrected. The magnetochemical
measurements were performed by the method of [5].
[(PhC≡C)3Cu]3Pr2(THF)6 + Me3SiI
→ PhC≡CCu + Me3SiC≡CPh + PhC≡CPrI2(THF)3.
The yields of the reaction products are close to
quantitative. The reaction results in the elimination of
phenylethynylcopper and two-stage dealkynylation of
(PhC≡C)3Pr fragment. It little differs from the reaction
of tri(phenylethynyl)praseodymium tristetrahydrofura-
nate with trimethylsilyl iodide [3], accompanied by the
formation not only of the mixed phenylethynyl lantha-
nide derivative, but also of praseodymium(III) iodide.
Similarly, ytterbium(II) phenylethynyl cuprate
reacts with trimethylsilyl iodide in 1:4 ratio at room
temperature in THF to give phenylethynylcopper and
trimethylsilyl phenylacetylenide in high yields and also
phenylethynylytterbium(II) and ytterbium(II) iodides
in yields of 65 and 23%, respectively.
504

REACTION OF YTTERBIUM(II) AND PRASEODYMIUM(III) PHENYLETHYNYL CUPRATES
505
spectrum (CDCl3), δ, ppm: 7.28–7.45 m (5Н), 0.10 s
[9Н, Si(CH3)3]. Found, %: С 75.46; Н 7.96. C11H14Si.
Calculated, %: С 75.86; Н 8.04.
The preparation, purification and separation of the
unstable in air compounds were carried out in eva-
cuated sealed ampules using the Schlenk techniques.
The organic solvents were purified by the known
methods [6]. THF and hexane were distilled over
sodium benzophenone, degassed, and placed in an
evacuated ampule with a pre-prepared sodium mirror.
The required amount of the solvent was collected by
condensation in a vacuum.
The reaction of [(PhC≡C)3Cu]3Pr2(THF)6 with tri-
methylsilyl iodide. To a solution of 2.12 g (1.16 mmol)
of [(PhC≡C)3Cu]3Pr2(THF)6 in 20 ml of THF was
added 1.39 g (6.96 mmol) of trimethylsilyl iodide. The
reaction mixture was kept at room temperature for
10 days. Phenylethynylcopper formed as a yellow precipi-
tate. Yield 91% (0.52 g, 3.19 mmol). It is identical to
the compound obtained in the previous experiment.
The rare-earth metals of Russian production of
99.90–99.99% purity were used.
THF was distilled off from the filtrate into a trap
cooled with liquid nitrogen. The trap contained
phenylacetylene (yield 5%, by GLC). To the residue
was added hexane. The solid residue was washed with
hexane (5 × 40 ml) and dried in a vacuum to a constant
mass. Yield of PhC≡CPrI2(THF)3 1.53 g (92%,
2.14 mmol), brown amorphous substance, insoluble in
hexane, decomp. 190°C. IR spectrum (mineral oil), ν,
cm–1: 2200 m (PhС≡С), 1880 w, 1790 w, 1458 s, 1379
s, 1251 s, 1074 m, 1029 s, 914 s, 757 m, 689 s; 1050
m, 843 m (coordinated THF). Found, %: Pr 18.98; I
35.35. C20H29I2O3Pr. Calculated, %: Pr 19.80; I 35.67.
The reaction of {[(PhC≡C)3Cu]Yb(THF)2}2 with
trimethylsilyl iodide. To a solution of 1.98 g
(1.44 mmol) of {[(PhC≡C)3Cu]Yb(THF)2}2 in 20 ml
of THF was added 1.15 g (5.76 mmol) of trimethylsilyl
iodide. The reaction mixture was kept at room
temperature for 10 days. A crystalline precipitate of
ytterbium(II) iodide was formed. Its diamagnetic state
was confirmed by the magnetochemical measurements.
The precipitate was separated, washed with THF, and
dried in a vacuum. Yield 23.6% (0.22 g, 0.34 mmol).
Found, %: Yb 26.67;
I 37.93. C12H24I2O3Yb.
Calculated, %: Yb 26.90; I 39.50.
The solvent was removed from the hexane extracts
to give Me3SiC≡CPh. Yield 66% (0.79 g, 4.59 mmol).
This compound is identical to that obtained in the
previous reaction.
THF was distilled off from the filtrate into a trap
cooled with liquid nitrogen. The trap contained 0.08 g
(0.86 mmol, 10%) of phenylacetylene, identified by GLC.
To the residue in the ampule was added benzene to
collect the phenylethynylcopper formed in 82.2% yield
(0.39 g, 2.37 mmol). Yellow amorphous substance,
decomp. 225°C. Found Cu, %: 38.60. C8H5Cu. Cal-
culated Cu, %: 38.79.
ACKNOWLEDGMENTS
This work was financially supported by the
Ministry of Education and Science.
REFERENCES
Benzene was distilled off from the filtrate into a
trap cooled with liquid nitrogen. To the residue was
added hexane. The solid residue was washed with
hexane (5×40 ml) and dried in a vacuum to a constant mass.
Yield of PhC≡CYbI(THF)3 1.15 g (65%, 1.86 mmol),
light brown amorphous substance, insoluble in hexane,
decomp. 200°C. IR spectrum (mineral oil), ν, cm–1:
2200 m (PhС≡С), 1880 w, 1790 w, 1461 s, 1379 s,
1300 s, 1071 m, 1026 s, 914 s, 757 m, 689; 1040 m,
840 m (coordinated THF). Found, %: Yb 30.50; I
21.39. C20H29IO3Yb. Calculated, %: Yb 28.04; I 20.58.
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The solvent was removed from the hexane extracts
to give Me3SiC≡CPh. Yield 62% (0.61 g, 3.55 mmol),
pale yellow oil, readily soluble in THF, benzene, bp
153°C (6 mm Hg) [7]. IR spectrum (mineral oil), ν,
cm–1: 3080 m, 3060 m, 3027 m, 2956 s; 2160 s (С≡С),
1950 w, 1598 m, 1488 s, 1444 m, 1251 s, 1100 s, 1029
1
m, 866 s, 843 s, 757 s, 689 s, 645 m, 535 s. Н NMR
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 3 2012