M. Duval, V. Deboos, Agnès Hallonet et al.
Journal of Catalysis 396 (2021) 261–268
2.6. NMR spectroscopy analyses
lized by different surfactants were measured and reported in
Table S1.
1H and 13C NMR spectra were recorded on a Brucker Avance III
400 MHz spectrometer at 400 MHz for 1H and 100 MHz for 13C in
CDCl3 with residual CHCl3 (1H, 7.26 ppm) or (13C, 77.16 ppm).
2.12. Synthesis of polyvinylpyrrolidone-stabilized Pd(0) suspension
reduced by NaBH4
2.7. pH measurements
To an aqueous solution (5 mL) of PVP (40000 wt) (21 mg, 5
equiv.), was added 1 mL of a freshly-prepared aqueous solution
of sodium borohydride (9.5 Â 10À5 mol, 2.5 equiv.). Then, this mix-
ture was quickly added under vigorous stirring to an aqueous solu-
tion (4 mL) of the metallic precursor Na2PdCl4Á6H2O (3.8 Â 10À5
mol, 1.0 equiv.). A color change from yellow to black was observed,
evidencing the reduction. The suspension was kept under stirring
for 12 h before use.
pH values of the suspensions were determined with a Mettler
Toledo pH meter without any dilution.
2.8. Zeta potential analyses
Zeta potential measurements were carried out by laser Doppler
electrophoresis, with Zetasizer Nano ZS90 equipment. Aqueous
suspensions of Pd(0) nanoparticles were diluted at a concentration
of 1.9 Â 10À3 mol.LÀ1. Analyses were performed in a cell (DTS1070,
150 mL) at 20 °C. The data was processed by the Zetasizer software.
2.13. General catalytic procedure
In a 50 mL pressure reactor, 10 mL of Pd(0) suspension
(0.038 mmol) and substrate (3.8 mmol) were introduced. In some
experiments, additives such as sodium hydroxide or hydrochloric
acid could be added to adjust the medium pH to the given value.
The autoclave was purged with H2 (5 bar, 3 times) and pressurized
to the given pressure. The reaction mixture was kept at the desired
temperature, under magnetic stirring during the desired reaction
time. Room temperature refers to 22–25 °C. At the end of the reac-
tion, the products were extracted with diethyl ether (3 Â 10 mL)
and the organic layer was washed with water to remove any trace
of acid or base (pH around 7). The crude mixture was analyzed by
GC-FID in diethyl ether with n-dodecane as internal standard. After
purification on column chromatography, the products were ana-
lyzed by 1H and 13C NMR spectroscopy. For the recycling experi-
ment, this aqueous phase was recovered after reaction and a new
batch of substrate (3.8 mmol) was introduced in the reaction for
another cycle, under same conditions.
2.9. Static multiple light scattering – Turbiscan technology
Static multiple light scattering analyses were carried out using
the Turbiscan Lab technology (Formulaction, Toulouse, France).
This apparatus is constituted of a near infrared light source (wave-
length ¼ 880 nm), and two synchronized detectors, which all move
vertically alongside the cylindrical glass sample cell. The light
source head scans the entire height of the sample (up to 55 mm),
and the detectors acquire transmission and backscattering data
every 40 mm. The measured photon fluxes are calibrated with a
non-absorbing scattering standard (calibrated polystyrene latex
beads) and a transmittance standard (silicon oil). The temperature
of the apparatus was regulated at 25.0 0.1 °C. The nanoparticle
suspensions were studied without any dilution and for each one
of them a scan was carried out every 4 h, along 7 days.
2.14. Scale-up for the production of FlorsantolÒ
2.10. UV-visible spectroscopy
These experiments were carried out using the facilities of the
DRT company (Castets, France). In a 1.2 L pressure reactor, the cat-
alyst and 40 g (0.21 mol) of 8-epoxy-2-methoxy-2,6-dimethyloc
tane (EMDO) were introduced in a molar substrate/Pd ratio of
100. The autoclave was purged with H2 and pressurized at 40 bar
of H2. The reactor was heated thanks to a jacket at 85 °C. The reac-
tion was conducted under mechanical stirring with hydrogen cir-
culation thanks to a hollow shaft during 7.2 h. At the end of the
reaction, the final products were isolated by solvent extraction (di-
ethyl ether) and analysed by GC-FID.
Measurements were performed in a quartz cuvette with diluted
sample, using a Jasco V750 spectrophotometer in the 190–900 nm
range (25 °C). The light source was a 340 nm deuterium/halogen
lamp.
2.11. TEM experiments
Transmission electron microscopy (TEM) images were recorded
with a JEOL TEM 100CXII electron microscope operated at an accel-
eration voltage of 100 kV, with a KeenView camera and the ITEM
software (1376 Â 1032 px). The samples were prepared by the
addition of a drop of the colloidal suspension on a copper grid
coated with a porous carbon film.
3. Results and discussion
3.1. Scope of substrates
2.11.1. Synthesis of ammonium-stabilized Pd(0) suspension reduced
by NaBH4
Pd nanoparticles were synthesized by chemical reduction of
sodium tetrachloropalladate (II) with sodium borohydride and effi-
ciently stabilized in water with N,N-dimethyl-N-cetyl-N-(2-
hydroxyethyl) chloride (HEA16Cl) in a surfactant/metal molar ratio
of 2.5, according to a procedure already reported [27,28]. The
Pd@HEA16Cl suspension was investigated for the hydrogenolysis
of various epoxides in water (Table 1). According to the substrates,
the dihydrogen pressure and the temperature were adapted. In this
work, the hydrogenation of epoxystyrene under mild conditions
(Table 1, Entry 1) afforded the targeted 2-phenylethanol (75%) as
main product, alongside phenylacetaldehyde (12%) and
phenylethane-1,2-diol (13%), both formed because of the slightly
acidic metal suspension (pH = 5.8). Two alkylphenyl epoxides as
The aqueous Pd(0) suspension ([Pd] = 3.8 mmol.LÀ1) was pre-
pared, according to a procedure adapted from the literature [27].
To an aqueous solution (5 mL) of a chosen quaternary ammonium
salt (9.5 Â 10À5 mol, 2.5 equiv.) was added 1 mL of a freshly pre-
pared aqueous solution of sodium borohydride (9.5 Â 10À5 mol,
2.5 equiv.). Then, this solution was quickly added under vigorous
stirring to an aqueous solution (4 mL) of the sodium tetra-
chloropalladate(II) hydrate Na2PdCl4Á6H2O (3.8 Â 10À5 mol, 1.0
equiv.) to obtain a colloidal suspension of Pd(0). The reduction,
indicating by a color change from yellow to black, occurred instan-
taneously. The suspension was kept under stirring during 12 h
before use as catalyst. Zeta potentials of Pd(0) suspensions stabi-
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