was filtered off, washed with water, 95% ethanol and finally
with diethyl ether. The yield of 1 was 2.73 g (ca. 82%). The
compound is moderately soluble in dichloromethane, acetoni-
trile and acetone but insoluble in ethanol, benzene and diethyl
ether. Found, C, 38.62; H, 2.65; N, 5.12; W, 32.84. Calc. for
C18H14N2O7W: C, 38.98; H, 2.52; N, 5.05 and W, 33.21%. IR
(KBr disc; cmꢂ1): 1590 (w), 1570 (w), 1550 (w), 1490 [s; n (C–
N)], 1470 (m), 1360 (s), 1310 (m), 1260 (w), 1100 [s; n (C–O)],
960 [s; n (WQO)], 880, 820 [s; n (O–O)], 760 (s), 635 (m), 580
(w), 520 (w), 510 (w). lmax(nm): 400 (e = 2760 Mꢂ1 cmꢂ1), 341
(4230).
[PPh4][WO3(QO)] 6. 6 was prepared by taking 1.0 mmol of
4 and 2 mmol of cyclopentene and adopting the same proce-
dure as for 3. The yield of 6 was 0.68 g (95%). The solubility of
the compound parallels that of 4. Found, C, 55.52; H, 3.62; N,
1.96; W, 25.52. Calc. for C33H26NO4W: C, 55.40; H, 3.60; N,
2.04; W, 25.69%. IR (KBr disc, cmꢂ1): 1575 (w), 1492 (s), 1462
(m), 1430 (m), 1365 (s), 1312 (s), 1250 (m), 1225 (w), 1160 (w),
1095 (vs), 968 (vs), 938 (m), 912 (m), 895 (s) [underlined
vibrations, n (WQO)], 805 (vs), 745 (s), 715 (s), 685 m), 640
(w). lmax(nm): 365 (e = 600 Mꢂ1 cmꢂ1), 276 (4860), 269
(5010).
Notably, the elemental analyses results of 5 and 6 are quite
close. This is due to their very close and at the same time high
molecular weight. However, their structural composition can
be differentiated by qualitative as well as quantitative chemical
analysis. 5 responds the starch iodide test in aqueous acetoni-
trile medium in the presence of H3BO3, where a blue-violet
colour develops, but 6 does not respond to this test. Moreover,
an acetonitrile solution of 5, when acidified with 1.5 N H2SO4
and treated with 0.1 N KMnO4, starts evolving O2 gas. When
gas evolution ceases, an excess of (NH4)2Fe(SO4)2 ꢀ 6H2O is
added to the above solution and the unreacted Fe21 deter-
mined by titration with 0.1 N KMnO4 which gives18 the %
O22ꢂ in 5. Anal. calc. for C33H26NO5W: 4.38%; found, 3.80%.
Another convincing proof that 5 contains O22ꢂ whereas 6 does
not is found in the fact that the former can stoichiometrically
epoxidize one mole of the olefinic compound (GC probe)
whereas 6 cannot. These indicate that 5 contains one peroxo
group but 6 does not.
[WO(O2)(QO)] 2. 1 (1.39 g; 2.5 mmol) was dissolved in
acetonitrile (20 cm3) and was refluxed for 20–25 min. The
solution was then cooled and diethyl ether was added to the
cold solution until the mixed solvent became 2 : 1 (v/v) with
respect to acetonitrile and diethyl ether, respectively. The
solution, on standing for 15 h, afforded orange crystals. Yield
1.2 g (92%). The solubility of the compound parallels that of
1. Found, C, 42.1; H, 2.4; N, 5.6; W, 35.2. Calc. for
C18H12N2O5W: C, 41.5; H, 2.3: N, 5.4 and W, 35.4%. IR
(KBr disc, cmꢂ1): 1590 (w), 1510 (s), 1470 (s), 1460 (sh), 1380
(s), 1330 (s), 1270 (m), 1240 (w), 1110 (s), 960 [s; n (WQO)],
890 [m; n (O–O)], 825 (m), 790 (w), 780 (sh), 755 (s), 630 (m),
530 (m), 500 (m). lmax(nm): 367 (e = 2870 Mꢂ1 cmꢂ1), 312
(4090).
[WO2(QO)2] 3. 0.52 g (1.0 mmol) of 2 and 0.068 g (1.0
mmol) of cyclopentene were dissolved in 10 ml acetonitrile in a
50 ml stoppered conical flask and the mixture was stirred for
about 2 h to complete the stoichiometric reaction (checked by
GC and the GC yield was found to be >99%). After the
reaction was over, the acetonitrile was expelled from the
reaction mixture by rotavapor. Diethyl ether was added to
the remaining solid to dissolve the corresponding epoxide. The
undissolved orange-red compound 3 was filtered off, washed
with diethyl ether and then vacuum dried. The yield of 3 was
0.48 g (95%). Its solubility was the same as that of 2. Found C,
43.05; H, 2.46; N, 5.60; W, 36.20. Calc. for C18H12N2O4W: C,
42.85; H, 2.38; N, 5.55; W, 36.48%. IR (KBr disc, cmꢂ1): 1580
(w), 1500 (m), 1480 (m), 1370 (s), 1310 (vs), 1250 (s), 1100 (vs),
940 [s; n (WQO)], 900 [s; n (WQO)], 825 (m), 790 (w), 740 (s),
640 (m), 530 (w). lmax(nm): 385 (e = 1460 Mꢂ1 cmꢂ1), 242
(3020).
Procedure of the epoxidation reaction
An acetonitrile (10 cm3) solution containing a given substrate
(ca. 10–15 mmol), NaHCO3 (2.5–3.75 mmol), tungsten cata-
lyst (0.01–0.001 mmol) and 30% H2O2 (30–40 mmol) in a flat-
bottom two-neck reaction flask with one neck fitted with a
reflux condenser (to check evaporation), the other neck being
closed with a septum, was stirred at room temperature (25 1C)
for a definite time period as quoted in the Table 1. As and
when required an aliquot of the reaction solution was with-
drawn from, or H2O2 added to, the contents of the flask with
the help of a syringe through the septum. The withdrawn 0.5
cm3 solution was subjected to multiple ether extraction and the
extract concentrated also up to 0.5 cm3 from which 1 ml
solution was withdrawn with the help of a syringe of 10 ml
capacity and injected to the GC port. The retention times of
the peaks were compared with those of commercial standards
and for GC yield calculation nitrobenzene was used as an
internal standard. For a few cases, especially for olefinic
alcohols, the identity of the product was confirmed by GC-
MS analysis. The isolated yield in a few cases (Table 1) was
obtained by multiple ether extraction of the reaction solution
after the reaction is over and then evaporating the ether and
acetonitrile by distilling at a mildly reduced pressure (using a
water aspirator), keeping over P2O5 in a desiccator and
weighing (when the GC yield was 98–99%) in a micro-balance
and the identity of the products was then confirmed by IR and
NMR probing. For lower % yields the liquid (for solid
epoxides obtained from liquid olefins, the former are simply
[PPh4][WO(O2)2QO] 4. The synthesis, characterization and
crystal structure have previously been reported.15
[PPh4][WO2(O2)(QO)] 5. 0.747 g (1.0 mmol) of 4 and 0.068
g (1.0 mmol) of cyclopentene, dissolved in 10 ml acetonitrile,
were stirred for about 2 h following the same procedure as
used for the preparation of 3. The yield of [PPh4][WO2(O2)
(QO)] 5 was 0.70 g (96%). The solubility of the compound
parallels that of 4. Found, C, 54.24; H, 3.53; N, 1.92; W, 24.94.
Calc. for C33H26NO5W: C, 54.10; H, 3.50; N, 1.9; W, 25.13%.
IR (KBr disc, cmꢂ1): 1636 (m), 1582 (m), 1499 (s), 1484 (m),
1470 (s), 1400 (s), 1320 (m), 1260 (m), 1160 (vs), 975 [s; n
(WQO)], 943 [m; n (O–O)], 917 (w), 900 [s; n (WQO)], 814
(vs), 751 (s), 722 (s), 690 (s), 645 (w), 586 (m), 526 (s), 445 (s).
l
max(nm): 365 (e = 1000 Mꢂ1 cmꢂ1), 275 (3000), 251 (5700).
ꢁc
This journal is the Royal Society of Chemistry the Centre National de la Recherche Scientifique 2006
482 | New J. Chem., 2006, 30, 479–489