4830 Organometallics, Vol. 15, No. 22, 1996
Eriksson et al.
recrystallized from hot ethanol. Commercial 2-bromostyrene
was used without further purification.
pure 6 in THF or toluene are remarkably stable, compared to
the instability of solutions containing 3 or 4. X-ray quality
crystals of 6 were grown from a toluene solution at -80 °C.
P r ep a r a tion of (vip h )MgBr (1) in THF . To a slight
excess of magnesium (0.16 g, 6.6 mmol) in 20 mL of THF was
2-bromostyrene (1.10 g, 6.0 mmol) added slowly. The reaction
started immediately, and the solution was cooled. The solution
was left to react under stirring during 12 h, in order to ensure
that all 2-bromostyrene had reacted. The solution was cen-
trifuged, and the brownish solution was withdrawn with a
syringe for further syntheses. In our experience, it is easier
to handle a THF solution of 1 than the solid reagent.
Evaporation under reduced pressure of the THF solution of 1
yielded a white solid that is sparingly soluble in toluene. All
attempts to grow X-ray quality cystals of 1 were unsuccessful.
P r ep a r a tion of [Mg(THF )2(vip h )2] (2). To 20 mL of a
0.30 M solution of (viph)MgBr in THF was added 6 mL
dioxane, and the resulting solution was stirred for 1 h. The
precipitate was removed by centrifugation and the solution
evaporated under reduced pressure to dryness. In order to
remove dioxane completely, THF (2 × 5 mL) was added and
the solution was evaporated to dryness. Yield: 1.05 g, 90%.
1H NMR (THF-d8, 20 °C): δ 5.23 (d, 1H, dCH2), 5.46 (d, 1H,
dCH2), 6.88(t, 1H, C6H4), 6.91(t, 1H, C6H4), 6.93(dd, 1H,
sCHd), 7.36 (d, 1H, C6H4), 7.64 (d, 1H, C6H4). X-ray quality
crystals of 2 were grown from a 1:5 THF/diethyl ether solution
at -80 °C.
P r ep a r a tion of [Mg(THF )6][Cu 5(vip h )2Br 4]2‚THF (3).
Purified CuCl (0.66 g, 6.7 mmol) was added to 20 mL of a 0.30
M THF solution of 1 at -30 °C. While the reaction solution
slowly warmed up, CuCl dissolved, yielding a yellow solution
that gradually darkens. At 10 °C the solution was brown, and
a white precipitate had formed. When dioxane (5 mL) was
added, the white precipitate dissolved yielding a green solu-
tion, and a gray precipitate formed. The green solution was
separated by centrifugation, and yellow crystals of 3 precipi-
tated in approximately 50% yield at 4 °C. Crystals of 3 are
sparingly soluble in THF, yielding unstable solutions. The
remainder of the green solution was evaporated to dryness
under reduced pressure and extracted with toluene to give 6
in low yield (<5%).
P r ep a r a tion of [Mg(THF )5Cl][Cu 5(vip h )4Br 2]‚THF (4).
Purified CuCl (0.48 g, 4.8 mmol) was added to 15 mL of a 0.30
M THF solution of 1 at -20 °C. While the reaction solution
was slowly warmed to -10 °C, CuCl dissolved, yielding a
yellow solution. When the solution was kept at -20 °C for
several weeks, yellow crystals of 4 formed in approximately
40% yield. Crystals of 4 are sparingly soluble in THF, yielding
unstable solutions.
P r ep a r a tion of [Cu (P P h 3)3Br ]‚THF (5). To a solution
of triphenylphosphine (0.58 g, 2.21 mmol) in 5 mL of THF were
added crystals of 3 (0.20 g, 0.09 mmol). After complete
dissolution by gentle heating, the solution was left at ambient
temperature. Colorless crystals of 5 formed after a few days.
Yield: 0.05 g, 55%.
P r ep a r a tion of [Cu 4(vip h )4] (6). Rou te A: F r om [Mg-
(THF )2(vip h )2] (2) a n d Cu Cl in THF . A solution of 2 (0.40
g, 1.07 mmol) in 3 mL of THF was slowly added to a suspension
of CuCl (0.22 g, 2.22 mmol) in 10 mL of THF and 3 mL of
dioxane, at 0 °C. The solution was kept at 0 °C, under stirring,
for 7 h. The green suspension was centrifugated and the
solution evaporated to dryness under reduced pressure. In
order to remove dioxane completely, THF (2 × 5 mL) was
added, and the solution was evaporated to dryness. The
remainder was extracted with toluene and the solution sepa-
rated by centrifugation and evaporated under reduced pressure
to dryness. The remaining white powder was washed with
cold hexane (3 × 5 mL) and dried under argon. Yield: 0.24 g,
65%. 1H NMR (THF-d8, 50 °C): δ 5.23 (d, 1H, dCH2), 5.92
(d, 1H, dCH2), 7.00 (t, 1H, C6H4), 7.19 (t, 1H, C6H4), 7.24 (dd,
1H, sCHd), 7.37 (d, 1H, C6H4), 7.92 (d, 1H, C6H4). Solid 6 is
air-sensitive but can be stored under argon at ambient
temperature without extensive decomposition. Solutions of
R ou t e B: F r om [Mg(THF )2(vip h )2] (2) a n d Cu Cl in
Tolu en e. To a solution of 2 (1.31 g, 3.49 mmol) in 50 mL of
toluene was added CuCl (0.82 g, 8,28 mmol) at 0 °C. The
solution was kept at ambient temperature, under stirring, for
12 h. The resulting suspension was centrifugated and the
solution evaporated to dryness under reduced pressure. The
residue was washed with three 5-mL portions of hexane and
dissolved in the minimum amount of THF at ambient tem-
perature. A white solid (6) was precipitated from this THF
solution by the addition of 25 mL of hexane and dried under
vacuum. Yield: 0.85 g, 73%.
Rou te C: F r om (vip h )MgBr /Eth er a n d Cu Br in Tolu -
en e. A 0.30 M (20 mL) THF solution of 1 was evaporated to
dryness under reduced pressure and washed with 10 mL of
hexane. The remaining solid was dissolved in 5 mL of diethyl
ether and evaporated to dryness under reduced pressure; this
procedure was repeated once. The remaining solid was
dissolved in 50 mL of toluene, and 1.72 g of CuBr (120 mmol)
was added at 0 °C. The solution turned yellow, and a white
precipitate was formed. After approximately 70 min a yellow
precipitate started to form, and the green reaction solution
was evaporated to dryness. The remainder was washed by
sonication with 10 mL of hexane, and the solid remainder was
treated with 10 mL of THF. To the resulting greenish solution
was added 50 mL of hexane, yielding a light-green powder (6).
Yield: 0.60 g, 30%.
NMR Sp ectr oscop y. All NMR spectra were recorded on
a Varian XL 400 spectrometer with a measuring frequency of
1
400 MHz H in THF-d8.
IR Sp ectr oscop y. Infrared spectra were collected, from
-100 °C to ambient temperature, with a Mattson Polaris FTIR
spectrometer, using a CaF2 mull cell with pentane as mulling
agent or a solution cell with CaF2 windows, at a resolution of
2 cm-1 and 10-100 scans.
X-r a y Cr ysta llogr a p h y. Gen er a l Deta ils. Crystal and
experimental data are summarized in Table 1. Crystals were
isolated, selected, and mounted, by the use of special low-
temperature methodology,20 under argon, at -150 °C, and
transferred (in Lindemann capillaries) under liquid nitrogen
to a Rigaku AFC6R diffractometer. Diffracted intensities were
measured using graphite-monochromated Mo KR (λ ) 0.710 69
Å) radiation from a RU200 rotating anode source operated at
9 kW (50 kV; 180 mA). The ω/2θ scan mode was employed,
and stationary background counts were recorded on each side
of the reflection, the ratio of peak counting time vs background
counting time being 2:1. Data were measured for 5 < 2θ <
50°, using an ω scan rate of 8-16°/min and a scan width of
(1.10 + 0.30 tanθ)°. Weak reflections (I < 10.0σ(I)) were
rescanned up to three times and counts accumulated to
improve counting statistics. The intensities of three reflections
monitored regularly after measurement of 150 reflections
confirmed crystal stability during data collection. Correction
was made for Lorentz and polarization effects. No correction
was made for the effects of absorption, owing to the inability
to measure and index the faces of the unstable crystals and a
failure to obtain a more satisfactory structural models from
empirically corrected data (by means of azimuthal scans with
transmission factors in the 0.90-1.00 range). However, care
was taken to select and cut the crystals so that the effects of
absorption were minimized. Cell constants were obtained by
least-squares refinement from the setting angles of 20 reflec-
tions in the range 15 < 2θ < 30°.
The structures were solved by direct methods (MITHRIL),22
and the hydrogens were located from difference maps or
introduced in calculated positions. All calculations were
(22) Gilmore, C. J . J . Appl. Crystallogr. 1984, 17, 42.
Eriksson, Henrik
