186
L.S. Nogueira et al. / Journal of Organometallic Chemistry 846 (2017) 185e192
tetracarbonyl complex and oxidised compounds have been studied
as catalysts or catalyst precursors for the epoxidation of cis-cyclo-
octene and the ethanolysis of styrene oxide. Particular attention has
been paid to the characterisation of solids recovered after catalytic
runs.
vacuum-dried. Yield: 0.45 g, 56%. Anal. Calcd for C17H17MoN3O4
(423.27): C, 48.24; H, 4.05; N, 9.93. Found: C, 48.18; H, 4.20; N,
9.79%. Selected FT-IR (KBr, cmꢃ1): 361 (s), 405 (w), 467 (w), 478 (w),
557 (m), 584 (m), 602 (m), 627 (w), 648 (m), 760 (vs), 791 (w), 883
(w), 958 (w), 1030 (w), 1157 (w), 1234 (m), 1336 (w), 1361 (m), 1439
(s),1460 (w),1498 (w),1523 (w),1606 (m),1824 (vs),1861 (vs), 2013
(vs), 2864 (m), 2933 (m), 2960 (w). 1H NMR (300.1 MHz, 295 K,
2. Experimental
CDCl3):
d
¼ 9.04 (qd, 1H, H-11), 7.83 (dt, 1H, H-9), 7.73 (td, 1H, H-8),
2.1. Materials and methods
7.60 (d, 1H, H-5), 7.26 (H-10, overlap with solvent peak), 6.81 (d, 1H,
H-4), 4.44 (t, 2H, N-CH2), 2.02 (m, 2H, CH2), 1.40 (m, 4H, CH2), 0.93
Hydrazine (N2H4$H2O, hydrate solution, 80%), sodium hydride
(60% dispersion in mineral oil), 1-iodopentane (98%), 1-butyl-3-
methylimidazolium (bmim) chloride (98%, Solchemar), 1-butyl-3-
methylimidazolium bis(trifluoromethylsulfonyl)imide (99%, Ioli-
tec), 1-butyl-3-methylimidazolium hexafluorophosphate (99%,
Iolitec), molybdenum hexacarbonyl, molybdenum trioxide (99.5%,
Analar), ammonium heptamolybdate tetrahydrate (Merck), 37%
hydrochloric acid, 30 wt% hydrogen peroxide, 5e6 M tert-butyl-
hydroperoxide in decane, cis-cyclooctene (95%, Alfa Aesar), cyclo-
octene oxide (99%), styrene oxide (98%), tetrahydrofuran (99.9%),
dichloromethane (puriss), 1,2-dichloroethane (99%), anhydrous
acetonitrile (99.8%), chloroform (99.8%), hexane (99%), pentane
(>95%, Carlo-Erba), acetone (99.5%), diethyl ether (99.8%) and
anhydrous absolute ethanol (ꢁ99.9%, Carlo-Erba) were acquired
from Sigma-Aldrich unless otherwise indicated, and used as
received. 2-[3(5)-Pyrazolyl]pyridine and 2-(1-pentyl-3-pyrazolyl)
pyridine (ppp) were prepared as described previously [26,27]. The
hybrid material with the composition [Mo2O6(ppp)] (3) was ob-
tained by the reaction of the complex [MoO2Cl2(ppp)] with water
[27]. Instead of performing the reaction in a Teflon-lined digestion
bomb [27], the reaction was carried out with water under reflux
(t, 3H, CH3) ppm. 13C NMR (75.4 MHz, 295 K, CD3CN):
d
¼ 223.13 (CO
cis), 222.62 (CO cis), 204.74 (CO trans), 153.62 (C-7), 152.38 (C-11),
151.77 (C-3), 139.37 (C-9), 135.58 (C-5), 124.91 (C-8), 122.50 (C-10),
105.53 (C-4), 54.21 (N-CH2), 31.12 (CH2), 29.15 (CH2), 22.88 (CH2),
14.08 (CH3) ppm.
2.2.2. [Mo8O24(2-(1-pentyl-3-pyrazolyl)pyridine)4] (2)
In a Schlenk tube, 5e6 M TBHP in decane (1.3 mL, ca. 7.1 mmol)
was added to a mixture comprising complex 1 (0.30 g, 0.71 mmol)
and CH2Cl2 (30 mL), and stirring was continued for 4 h under N2 at
room temperature. The resultant off-white solid was recovered by
filtration, washed with diethyl ether (2 ꢄ 30 mL), and finally
vacuum-dried. Yield: 0.08 g, 45%. Anal. Calcd for C52H68Mo8N12O24
(2012.68): C, 31.03; H, 3.41; N, 8.35. Found: C, 30.91; H, 3.57; N,
8.48%. TGA revealed a residual mass of 57.5% at 600 ꢀC (calcd, for
MoO3: 57.2%). Selected FT-IR (KBr, cmꢃ1): 357 (w), 374 (w), 405 (w),
426 (w), 524 (w), 559 (w), 667 (vs), 702 (s), 775 (s), 804 (s), 843 (w),
910 (s), 942 (s), 1024 (w), 1055 (w), 1080 (w), 1099 (m), 1161 (w),
1192 (w), 1236 (m),1371 (m),1442 (s), 1466 (m),1504 (m),1543 (w),
1570 (w), 1612 (s), 1630 (m), 1741 (w), 2865 (m), 2927 (m), 2956
(m), 3116 (m). Selected FT-Raman (cmꢃ1): 203 (m), 220 (sh), 933
(vs), 962 (m), 985 (w), 1021 (m), 1235 (w), 1369 (m), 1419 (m), 1438
(w), 1502 (m), 1534 (s), 1569 (s), 1609 (s).
conditions. The octamolybdate salt [bmim]4[b-Mo8O26] (5) was
prepared by addition of [bmim]Cl to an acidified solution of
ammonium heptamolybdate [28].
Microanalyses for C, H and N were carried out at the Department
of Chemistry, University of Aveiro, with a Truspec Micro CHNS 630-
200-200 elemental analyser. Powder X-ray diffraction (PXRD) data
were collected at ambient temperature using a PANalytical Empy-
rean instrument equipped with a PIXcel 1D detector set at 240 mm
2.2.3. [MoO(O2)2(2-(1-pentyl-3-pyrazolyl)pyridine)] (4)
A mixture of MoO3 (0.25 g, 1.73 mmol) and 30% H2O2 (2.50 mL,
24.5 mmol) was stirred for 3 h at 60 ꢀC under N2. The resultant
yellow solution was cooled in an ice-bath and then added slowly to
a Schlenk tube containing ppp (0.37 g, 1.73 mmol). A yellow solu-
tion and paste were obtained at this stage. After the addition of H2O
(4 mL), the mixture was stirred until a yellow solid was obtained,
which was recovered by filtration, washed with H2O (2 ꢄ 5 mL) and
pentane (2 ꢄ 4 mL), and finally vacuum-dried. Yield: 0.41 g, 60%.
Anal. Calcd for C13H17MoN3O5 (391.23): C, 39.91; H, 4.38; N, 10.74.
Found: C, 40.15; H, 4.45; N, 10.65%. Selected FT-IR (KBr, cmꢃ1): 320
(w), 407 (w), 432 (w), 534 (m), 546 (m), 585 (m), 627 (w), 642 (w),
660 (m), 737 (w), 779 (s), 800 (w), 863 (s), 881 (m), 948 (s), 1022
(w), 1053 (w), 1093 (m), 1103 (m), 1151 (w), 1163 (w), 1198 (w), 1234
(m), 1263 (w), 1300 (w), 1332 (w), 1361 (m), 1442 (m), 1468 (m),
1504 (m), 1531 (w), 1574 (w), 1610 (m), 2866 (m), 2935 (m), 2951
(m), 3142 (w), 3136 (w). Selected FT-Raman (cmꢃ1): 221 (w), 252
(m), 281 (m), 301 (m), 318 (w), 406 (w), 471 (w), 502 (w), 532 (m),
550 (w), 584 (w), 642 (w), 661 (w), 702 (w), 798 (w), 866 (w), 882
(m), 953 (s), 1022 (m), 1053 (w), 1093 (w), 1102 (w), 1119 (w), 1163
(w), 1331 (m), 1362 (m), 1421 (m), 1441 (m), 1504 (m),1535 (s), 1572
(m), 1608 (m), 2730 (w), 2861 (m), 2906 (m), 2997 (w), 3065 (m),
3088 (w), 3134 (m).
from the sample. Cu-Ka
X-radiation
(
l1
¼
1.540598 Å;
1,2
l2 ¼ 1.544426 Å) filtered with a nickel foil was used along with a
standard transmission sample holder. Working operating condi-
tions for the X-ray tube: 45 kV and 40 mA. Intensity data were
collected in continuous mode in the ca. 3.5 ꢂ 2
q
ꢂ 70ꢀ range.
Thermogravimetric analysis (TGA) was performed using a Shi-
madzu TGA-50 system at a heating rate of 5 ꢀC minꢃ1 under air. FT-
IR spectra were recorded on a Mattson 7000 FT-IR spectrometer
using KBr pellets. Attenuated total reflectance (ATR) FT-IR spectra
were measured using a Specac Golden Gate Mk II ATR accessory
having a diamond top plate and KRS-5 focusing lenses. FT-Raman
spectra were recorded on an RFS-100 Bruker FT-Spectrometer
equipped with a Nd:YAG laser with an excitation wavelength of
1064 nm. 1H and 13C solution NMR spectra were recorded on Bruker
Avance 300 and 400 spectrometers. Chemical shifts are quoted in
ppm from TMS.
2.2. Synthesis
2.2.1. [Mo(CO)4(2-(1-pentyl-3-pyrazolyl)pyridine)] (1)
2.3. Epoxidation tests
In a Schlenk tube, Mo(CO)6 (0.50 g, 1.89 mmol) and ppp (0.41 g,
1.90 mmol) were added to toluene (30 mL) and the mixture was
refluxed under N2 for 45 min. After concentrating the resultant
solution, hexane (15 mL) and pentane (5 mL) were added, and the
mixture was left undisturbed overnight. The resultant yellowish
green precipitate was washed with pentane (2 ꢄ 15 mL) and finally
The typical epoxidation experiments were carried out in 10 mL
borosilicate batch reactors, equipped with an appropriate PTFE-
coated magnetic stirring bar (1000 rpm) and a valve for sampling.
The heating source was a thermostatically controlled oil bath
(55 ꢀC). The reactors were charged with the (pre)catalyst (amount