New Pd-phosphorus ylide complexes based on FC60 as heterogeneous nano-catalyst for H/D exchange reaction

Article abstract of DOI:10.1002/aoc.6139

In this account, new Pd(0) complexes of phosphorus ylides based on fullerene C₆₀ (FC₆₀) were synthesized and utilized as the first fullerene-based heterogeneous nano-catalysts for H/D exchange reaction. Four new palladacyclopropa-[60]fullerene complexes 1–4, [(η²-C₆₀)Pd(Y^1–4)₂] (Y¹ = PPh₃CHC(O)C₆H₄-p-NO₂, Y² = PPh₃CHC(O)C₆H₄-p-CH₃, Y³ = (p-tolyl)₃P-CHC(O)C₆H₄-p-NO₂, and Y⁴ = (p-tolyl)₃P-CHC(O)C₆H₄-p-CH₃), were prepared through dissolving the related α-keto stabilized phosphorus ylide in toluene solution in the presence of FC₆₀ and Pd (dba)₂ (dba = dibenzylideneacetone). All of the complexes were characterized using Nuclear magnetic resonance (NMR) (¹H, ¹³C, and ³¹P), Infrared spectroscopy (IR), Ultraviolet-visible spectroscopy (UV-visible), fluorescence, Electrospray Ionisation Mass Spectrometry (ESI-MS), and Energy-dispersive X-ray spectroscopy (EDX) spectroscopies, and scanning electron microscopy (SEM) and TEM techniques. The data proved that FC₆₀ and two ylides were coordinated to Pd(0) center through two hexagons and two ylidic carbon atoms, respectively. An evaluation was also performed to compare the catalytic activity of synthesized Pd complex 1 and a conventional heterogeneous catalyst, 10% Pd on carbon, in H/D exchange reaction. The results indicate that the process of H/D exchange reaction in aromatic rings of benzoic acid derivatives progressed more efficiently by Pd complex 1.

Full text of DOI:10.1002/aoc.6139

Received: 19 September 2020
DOI: 10.1002/aoc.6139
Revised: 3 December 2020
Accepted: 14 December 2020
F U L L P A P E R
New Pd-phosphorus ylide complexes based on FC60 as
heterogeneous nano-catalyst for H/D exchange reaction
Abed Yousefi
| Seyyed Javad Sabounchei
| Ali Hashemi
Faculty of Chemistry, Bu-Ali Sina
University, Hamedan, Iran
In this account, new Pd(0) complexes of phosphorus ylides based on fullerene
C60 (FC60) were synthesized and utilized as the first fullerene-based heteroge-
neous nano-catalysts for H/D exchange reaction. Four new palladacyclopropa-
[60]fullerene complexes 1–4, [(η2-C60)Pd(Y1–4)2] (Y1 = PPh3CHC(O)C6H4-p-
NO2, Y2 = PPh3CHC(O)C6H4-p-CH3, Y3 = (p-tolyl)3P-CHC(O)C6H4-p-NO2,
and Y4 = (p-tolyl)3P-CHC(O)C6H4-p-CH3), were prepared through dissolving
the related α-keto stabilized phosphorus ylide in toluene solution in the pres-
ence of FC60 and Pd (dba)2 (dba = dibenzylideneacetone). All of the complexes
were characterized using Nuclear magnetic resonance (NMR) (1H, 13C, and
31P), Infrared spectroscopy (IR), Ultraviolet-visible spectroscopy (UV-visible),
fluorescence, Electrospray Ionisation Mass Spectrometry (ESI-MS), and
Energy-dispersive X-ray spectroscopy (EDX) spectroscopies, and scanning elec-
tron microscopy (SEM) and TEM techniques. The data proved that FC60 and
two ylides were coordinated to Pd(0) center through two hexagons and two
ylidic carbon atoms, respectively. An evaluation was also performed to com-
pare the catalytic activity of synthesized Pd complex 1 and a conventional het-
erogeneous catalyst, 10% Pd on carbon, in H/D exchange reaction. The results
indicate that the process of H/D exchange reaction in aromatic rings of benzoic
acid derivatives progressed more efficiently by Pd complex 1.
Correspondence
Seyyed Javad Sabounchei, Faculty of
Chemistry, Bu-Ali Sina University,
Hamedan 65174, Iran.
Email: jsabounchei@yahoo.co.uk
Funding information
Bu Ali Sina University
K E Y W O R D S
fullerene C60, H/D exchange reaction, heterogeneous nano-catalyst, palladium complexes,
phosphorus ylide
1 | INTRODUCTION
the preparation of advanced materials with the enhanced
performance.[5a–c] For example, deuterated conjugated
The synthesis of deuterated organic compounds plays an
outstanding part in organic chemistry since the H/D
exchange reactions can be often led to altering physico-
chemical properties of molecules.[1a–e] These selective iso-
topically labeled or fully deuterated compounds are
widely applied in various scientific fields such as mecha-
nistic investigation of chemical reactions,[2a,b] studying
the catalytic/metabolic pathways,[3a,b] utilizing as a sol-
vent or internal standards for qualitative/quantitative
nuclear magnetic resonance (NMR) analyses,[4a,b] and
aromatic/heterocyclic polymers which are used in
organic light-emitting diodes (OLEDs) have increased
substantially the neutron scattering length density in
comparison with their equivalent protonated forms.[5a]
Furthermore, two kinds of the most important deuterated
drugs, deutetrabenazine and deuterated lisofylline, have
shown promising results in clinical trials for treatment of
chorea associated with Huntington's disease and diabetic
nephropathy, respectively.[5b,c] According to these posi-
tive developments, the issue of the definition of new
Appl Organomet Chem. 2021;35:e6139.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6139

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YOUSEFI ET AL.
synthetic protocols for the full or selective deuteration of
organic compounds has received much attention in the
last decade.[6a–d]
Application of transition metal catalysts for activation
of C–H bonds in H/D exchange reactions have emerged
as an efficient and powerful methodology for the synthe-
sis of deuterated organic compounds.[7a–d] Although both
homogeneous and heterogeneous transition metal cata-
lysts were found to be effective for the H/D exchange
reaction,[8a–d] each of them has its own advantages or dis-
advantages. However, the most reported homogenous
reactions have been focused on the selective deuteration
of organic compounds by iridium, rhodium, and ruthe-
nium complexes as an efficient catalyst[9a–c]; the full deu-
teration of molecules is feasible by the heterogeneous
reactions, commonly using palladium- and platinum-
based catalysts.[10a–c] The performances of Pd/C and Pt/C
traditional catalysts for the incorporation of deuterium
into the C–H bonds of aromatic rings have been exten-
sively investigated, but they are often limited to activation
with H2 gas.[11a–d] Additionally, these catalytic systems
need to be heated above the boiling point of the solvent
in high-pressure/high-temperature sealed tubes and also
usually require a vast amount of the catalyst (20% w/w of
Pt/C 5% and 10% w/w Pd/C 10%).[11a–d] To overcome
these drawbacks of conventional heterogeneous catalysts,
the use of specific heterogeneous nano-catalysts with
enhanced catalytic activity may be beneficial.
In this regard, FC60-based palladium complexes can
be used as both homogeneous and heterogeneous nano-
catalysts in some catalytic reactions.[12a–c] Recently, the
use of FC60-based Pd(0) complexes of phosphorus ylides
has been reported as an efficient nano-catalyst for homo-
and heterogeneous Suzuki and Heck coupling reactions
in our group.[13a–d] These complexes are highly soluble in
benzene, chloroform, and DMF, which can act as homo-
geneous catalysts in these reaction media.[13b] Generally,
these nano-catalysts are insoluble in water and methanol,
and the reaction is catalyzed via a heterogeneous
pathway.[13a] The synthesis, full characterization, and use
of such new FC60-based Pd(0) complexes of phosphorus
ylides (Figure 1) as heterogeneous nano-catalysts for H/D
exchange reaction in aromatic rings of benzoic acid deriv-
atives in heavy water is the aim of this report.
FIGURE 1 FC60-based Pd(0) complexes of phosphorus ylides
as heterogeneous nano-catalyst for H/D exchange reaction in
aromatic rings of benzoic acid derivatives in heavy water
Pd(0) complexes was carried out under N2 atmosphere
1
using standard Schlenk techniques. The H, 13C, and 31P
NMR spectra were recorded on Bruker Avance 400 MHz
and Jeol 90 MHz spectrometers in CDCl3 or DMSO-d6 as
solvent at 25ꢀC. IR spectra were recorded on KBr pellets
using a Shimadzu 435-U04 spectrophotometer in the
region of 4000–400 cm−1. UV–visible spectra were
recorded between 200 and 800 nm using a Perkin voyager
DE-PRO spectrometer, and the fluorescence emission
spectra were performed on a Varian Cary spectrofluo-
rometer. Scanning electron microscopy (SEM) and trans-
mission electron microscopy (TEM) images were
conducted using VEGA TESCAN and Zeiss-EM10C-
100 K instrument, respectively. Thermal analyses Ther-
mogravimetric analysis (TGA), Derivative ther-
mogravimetric analysis (DTG), Differential thermal
analysis (DTA) and Differential scanning calorimetry
(DSC) were performed on a Rheometric Scientific SDT
Q600 V20.9 and carried out under a nitrogen atmosphere
at 25ꢀC with a heating rate of 10ꢀC up to 1000ꢀC. X-ray
diffraction (XRD) patterns were obtained by a Panalytical
X' Pert Pro apparatus in the range of 2θ: 5–80ꢀ. Inductive
coupling plasma mass spectrometer (ICP-MS) was carried
out on an Agilent 7700x apparatus.
2.2 | Synthesis of complexes
The solution of Pd (dba)2 (0.029 g, 0.05 mmol) in toluene
(3 ml) was added to a FC60 (0.036 g, 0.05 mmol) toluene
solution (12 ml) and stirred, which results immediately
in formation of a brown suspension. After that, a toluene
solution of phosphorus ylide (0.05 mmol, 5 ml) was
injected into the resulting suspension. The reaction mix-
ture was stirred for 24 h at 80ꢀC, and a deep green solu-
tion was obtained, which was layered with n-hexane
(60 ml) overnight. Afterward, the solid residue was
2 | EXPERIMENTAL
2.1 | Materials and methods
Phosphorus ylides Y1–4 were prepared according to the
literature method.[14a,b] [Pd (dba)2] complex was pre-
pared as previously published procedure.[15] Synthesis of

YOUSEFI ET AL.
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triturated with diethyl ether to obtain the corresponding
FC60-based Pd(0) complexes of phosphorus ylides as dark
green solids.
IR absorption in KBr (cm−1): 1670 (CO). 1H NMR
(89.6 MHz, CDCl3) δH (ppm): 2.43 (s, CH3, tolyl); 2.67
(s, CH3); 5.39 (br, CH, 2H); 7.27–7.74 (m, 16H, Ar). 31P
NMR (36.26 MHz, CDCl3) δP (ppm): 23.4 (s, PPh3). 13C
NMR (62.89 MHz, CDCl3) δC (ppm): 21.6 (s, CH3, tolyl);
24.9 (s, CH3); 50.8 (d, CH); 119.9–135.0 (Ar); 140.3–148.6
(FC60); ≈191.2 (s, CO). UV–Vis in toluene λmax (nm):
442, 615, 662. Fluorescence in toluene λmax (nm): 437.
2.2.1 | Data for [(η2-C60)Pd(Y1)2] (1)
Yield: 76%, M.p: >300ꢀC. Anal. Calc. for C112H4N2O6P2Pd
(%): C, 80.17; H, 2.40; N, 1.67. Found: C, 80.96; H,
2.34; N, 1.59. Selected IR absorption in KBr (cm−1): 1677
(CO). 1H NMR (89.6 MHz, CDCl3) δH (ppm): 5.28 (d, CH,
2JP–H = 19.58 Hz); 7.38–8.16 (m, 17H, Ar). 31P NMR
(36.26 MHz, CDCl3) δP (ppm): 24.3 (s, PPh3). 13C NMR
(62.89 MHz, CDCl3) δC (ppm): 53.5 (d, CH); 123.1–133.1
(Ar); 139.3–148.2 (FC60); 188.8 (s, CO). UV–Vis in toluene
λmax (nm): 440, 620, 659. Fluorescence in toluene λmax
(nm): 447. ESI-MS (m/z): calcd. For C112H4N2O6P2Pd
[M + 1]+: 1677, found: 1679.
2.3 | Typical procedure for deuteration
reactions
In a round-bottom flask containing benzoic acid deriva-
tive (1 mmol) in D2O (20 ml), 50 mg of catalyst (1 mmol)
was added, and the mixture stirred for 24 h under atmo-
spheric conditions at the temperature of 100ꢀC. After-
ward, the mixture of the reaction was filtrated and
extracted three times with Et2O (10 ml) and H2O (5 ml).
The combined organic layers were dried over anhydrous
MgSO4, filtrated, and concentrated in vacuum to give the
deuterated benzoic acid derivative.
2.2.2 | Data for [(η2-C60)Pd(Y2)2] (2)
Yield: 81%, M.p: >300ꢀC. Anal. Calc. for C114H46O2P2Pd
(%): C, 84.73; H, 2.87. Found: C, 85.16; H, 2.82. Selected
IR absorption in KBr (cm−1): 1679 (CO). 1H NMR
(89.6 MHz, CDCl3) δH (ppm): 2.57 (s, CH3); 5.34 (d, CH,
3 | RESULTS AND DISCUSSION
3.1 | Synthesis
2
2H, JP–H = 6.27 Hz); 7.19–7.96 (m, 19H, Ar). 31P NMR
(36.26 MHz, CDCl3) δP (ppm): 24.8 (s, PPh3). 13C NMR
(62.89 MHz, CDCl3) δC (ppm): 19.7 (s, CH3); 50.1
(d, CH); 113.1–134.8 (Ar); 139.5–148.3 (FC60); 190.6
(s, CO). UV–Vis in toluene λmax (nm): 443, 618, 663.
Fluorescence in toluene λmax (nm): 419.
At first, the toluene solution of phosphorus ylides Y1–4
reacted with [C60Pd]x, which was achieved by in situ
reaction of FC60 with the organometallic precursor Pd
(dba)2, leading new palladacyclopropa-[60]fullerene com-
plexes 1–4, [(η2-C60)Pd(Y1–4)2]. Although these complexes
are soluble in toluene, chloroform, and DMF, they are
insoluble in n-hexane, methanol, and water. As a result
of this solubility property, the precipitated complexes 1–4
were isolated from reaction media in pure form,
through the layering of toluene solution with n-hexane
overnight, without utilizing any purification technique.
Notably, a one-pot reaction of the above reactants
leads to the formation of undesirable palladium
complexes or methanofullerene side products.[16a,b] Based
on the known chemistry of palladium(0)-[60]fullerene
complexes,[12a–c,13a–d] an implicit mechanism is proposed
for the formation of these complexes (Scheme 1).
2.2.3 | Data for [(η2-C60)Pd(Y3)2] (3)
Yield: 74%, M.p: >300ꢀC. Anal. Calc. for
C
118H52N2O6P2Pd (%): C, 80.43; H, 2.97; N, 1.59.
Found: C, 80.96; H, 2.84; N, 1.56. Selected IR absorption
1
in KBr (cm−1): 1669 (CO). H NMR (89.6 MHz, CDCl3)
δH (ppm): 2.43 (s, CH3); 5.09 (d, CH, 2H, 2JP–H = 1.79 Hz);
7.26–8.11 (m, 17H, Ar). 31P NMR (36.26 MHz, CDCl3)
δP (ppm): 24.1 (s, PPh3). 13C NMR (62.89 MHz, CDCl3)
δC (ppm): 21.8 (s, CH3); 53.6 (d, CH); 114.5–135.1 (Ar);
139.5–151.0 (FC60); 191.2 (s, CO). UV–Vis in toluene λmax
(nm): 448, 620, 665. Fluorescence in toluene λmax
(nm): 434. ESI-MS (m/z): calcd. For C118H52N2O6P2Pd
[M + 1]+: 1762, found: 1765.
3.2 | Characterization
2.2.4 | Data for [(η2-C60)Pd(Y4)2] (4)
The structure of products was fully corroborated by FT-
1
IR, H, 13C, and 31P NMR spectroscopies. Further con-
Yield: 79%, M.p: >300ꢀC. Anal. Calc. for C120H58O2P2Pd
ventional techniques such as SEM and TEM analysis and
(%): C, 84.78; H, 3.44. Found: C, 84.96; H, 3.38. Selected
UV–visible, fluorescence, ESI-MS, EDX, and XRD

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YOUSEFI ET AL.
SCHEME 1 Synthesis of palladacyclopropa-[60]fullerene complexes 1–4
spectroscopies were also used for the characterization of
the new nano-catalysts (for experimental details, see the
Supporting Information).
agreement with ylidic carbon coordination to Pd cen-
ter.[18] Analogously, the 13C NMR spectra of complexes
indicate the coordination of phosphorus ylides occurs
through the methine carbon atom. The lower field
observations in 13C NMR spectra of complexes for the
ylidic carbon atom and carbonyl group signals com-
pared to the parent ylides suggest the C-coordination of
the ligands to Pd atom.[13a] Due to the coordination of
Pd atom to FC60, the high symmetry of fullerene skele-
ton was reduced, and the characteristic 13C NMR signal
of FC60 (143 ppm)[19] was split into many more peaks
around 140–150 ppm. 31P NMR is the best method to
determine the changes in the electronic environment of
phosphorus nuclei. Coordination of ylide through the
methinic carbon atom to Pd center leads to conversion
of P=C double bond to P–C single bond, which causes
a large downfield shift for the phosphorus atom of
PCH group.[20] Hence, the 31P NMR spectra represent a
singlet peak around 24 ppm for all complexes, which
shifted to downfield in comparison with parent ylides
(12–14 ppm) (Figure 2).
3.2.1 | FT-IR spectroscopy
The prominent feature of the IR spectra of these com-
plexes is the high-frequency shift of ν (CO) in phosphorus
ylide moiety compared to the free ligands. This could be
attributed to the C=O bond strength as a result of coordi-
nation of ylides through the ylidic carbon.[17] Moreover,
FT-IR spectra show the characteristic peaks for fullerene
absorptions around 525, 580, 1180, and 1430 cm−1, con-
firming the covalent attachment of fullerene to the
palladium core.
3.2.2 | 1H, 13C and 31P NMR
spectroscopies
The only expectable change in 1H NMR spectra of
complexes is the significant downfield shift of methinic
proton of phosphorus ylide moiety in comparison with
their free ligands. As seen from 1H NMR spectra, a
shift from about 4 ppm in free ligands to around
5 ppm in complexes for methinic proton signal is in
It must be noted that the O-coordination of the ylide
generally leads to the formation of cisoid and transoid
isomers, giving rise to two different sets of signals in all
NMR spectra.[21] Table 1 summarizes the IR and NMR
spectral data for complexes 1–4 and related phosphorus
ylides.

YOUSEFI ET AL.
5 of 12
FIGURE 2 31P NMR spectra of complexes 1–4 and their parent ylides Y1–4
TABLE 1 Spectroscopic data for complexes 1–4 and related ylides Y1 − 4
δ (PCH) ppm (1H
Compounds NMR)
δ (PCH) ppm (13C
NMR)
δ (PCH) ppm (31P
NMR)
δ (CO) ppm (13C
NMR)
ν (CO) cm−1
(IR)
1
2
3
4
5.28 {4.51}
5.34 {4.36}
5.09 {4.47}
5.39 {4.39}
53.5 {43.4}
50.1 {42.1}
53.6 {46.1}
50.8 {43.1}
24.3 {14.2}
24.8 {12.9}
24.1 {13.1}
23.4 {12.8}
188.8 {181.8}
190.6 {186.0}
191.2 {181.1}
191.2 {188.6}
1677 {1529}
1679 {1599}
1669 {1600}
1670 {1598}
*Data in braces are related to the spectroscopic data of parent ylides Y1–4
.
3.2.3 | UV–visible and fluorescence
observed emission bond in the FC60 spectrum is mainly
due to the π ! π* transitions, whereas the emission
bonds in complexes are attributed to the new transitions
from the excited state of the ligands (π*) to their ground
state (π), LLCT, and transition from the excited state of
the ligands (π*) to the ground state of the metal orbital
(d-block), ligand-to-metal charge-transfer (LMCT)
complex.[22]
spectroscopies
As shown in Figure 3, the results of UV–visible spectros-
copy of complexes in chloroform show three intense
broad bands with maxima at about 445, 620, and 660 nm,
related to metal to ligand charge transfer, metal-to-ligand
charge-transfer (MLCT) complex, (π ! π*/n ! π*). The
observed peaks are in different patterns than those found
in pure FC60, which suggest the complexation of palla-
dium to fullerene. These data are in agreement with such
η2-C60PdL2 complexes (L = phosphine ligand) and clarify
the η2-coordination of Pd center to the fullerene cage.[13d]
Fluorescence spectroscopy can be also used as a com-
plementary method for monitoring the molecular
changes occurring during the complexation of ylide and
FC60 to Pd metal center. The fluorescence spectra of pure
fullerene show the maximum emission of FC60 at
712 nm, which it was distinctly blue-shifted for com-
plexes ones (λmax = 437–447 nm) (Figure 4). The
3.2.4 | Thermal stability analyses
To investigate the thermal stability of the new nano-
catalyst 1, TGA, DTG, DTA, and DSC analyses were con-
ducted in an inert atmosphere. As shown in Figure 5a,
the TG diagram for FC60, the light mass losing (4.6 wt%)
below 200ꢀC can be attributed to the evaporation of
absorbed solvents such as water and toluene. A thermal
decomposition starting after 300ꢀC, with a weight loss of
about 95%, can be assigned to carbon cage and

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YOUSEFI ET AL.
FIGURE 3 The UV–Vis spectral data of FC60 and complexes 1–4 in toluene
FIGURE 4 The fluorescence emissions of FC60 and complexes 1–4 in toluene
amorphous carbon decompose in fullerene. (Figure 5b),
the heating of the compound from 300ꢀC to 430ꢀC
resulted in 57% weight loss, due to the removal of Pd-
phosphorus functional ligands. The second weight loss
occurs at temperature range of 450–650ꢀC which is
related to the decomposition of FC60. (see other thermal
analyses in Supporting Information).
3.2.5 | EDX and ESI-MS spectroscopies
The proposed structure for Pd complexes was supported
by EDX and ESI-MS analyses. The EDX measurements of
complexes 1 and 2 demonstrate the presence of Pd, O,
P, N, and C elements, as expected. The Inductively
coupled plasma - optical emission spectrometry (ICP-

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7 of 12
FIGURE 5 TGA spectra of (a) FC60, and
(b) palladium(0)-[60]fullerene complex 1
OES) analysis has also been applied to obtain an insight
into the accurate amount of Pd in complex 1 which calcu-
lated about 7.45 wt%. In agreement with the structural
formula, the ESI-MS spectra of complexes 1 and 3 show
the molecular ions at m/z 1679 and 1765, which strongly
supported the proposed molecular formula consisting of
FC60, Pd, and ylide units in 1:1:2 stoichiometry ratio (see
Supporting Information).
preserved during the functionalized method. However,
the diffraction peaks were labeled and indexed in about
40, 45, 70, and 80 (can be assigned to the diffraction from
the four reflection indexes of (111), (200), (220), and
(311), respectively) clearly detected the crystalline struc-
ture of complex 1 related to pure FC60 particle which has
irregular and amorphous shapes. It has also confirmed
the presence of palladium atom in complex 1.
3.2.6 | X-ray powder diffraction
3.2.7 | SEM and TEM analysis
The crystalline phase and the purity of the prepared
materials FC60 and [(η2-C60)Pd(Y1)2] are described in
Figure 6 with a diffraction angle (2θ) measured in the
range of 5–80. Figure 6a shows the XRD patterns of the
pure FC60 with two diffraction reflections in different
intensities, at 2θ = 20 and 10 related to carbon atom. The
XRD patterns of [(η2-C60)Pd(Y1)2] (Figure 6b) also depict
supplementary peaks corresponding to the FC60 which
means that the morphology and crystallinity of FC60 were
The SEM analysis was applied to study the morphology
of the synthesized palladacyclopropa-[60]fullerene com-
plexes. To do this, a comparison was made between the
SEM images of pure FC60 and complex 1. The results
showed the pure FC60 particles have irregular shapes and
were agglomerated together, so it was difficult to obtain
their average particle size. Conversely, the formation of
sintered grains with the 25–40 nm size range was appar-
ent in the SEM images of complex 1 (Figure 7).
FIGURE 6 XRD patterns of (a) FC60 and
(b) [(η2-C60)Pd(Y1)2]

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YOUSEFI ET AL.
FIGURE 7 SEM images of (a) pure FC60, and (b) complex 1
TEM images for complex 1 are also presented in
Figure 8. As shown in the bright-field image, Pd particles
were observed in the form of dark small objects. The Pd-
FC60 nanoparticles exhibit nearly spherical morphology
in uniform size and high concentration with a mean par-
ticle diameter of approximately 10–30 nm. TEM images
show that the fullerene-functionalized palladium
nanoparticles almost possess spherical morphology with
relatively good monodispersity.
deuterium content on aromatic ring was performed by
1H NMR analysis, using acetonitrile as an internal stan-
dard. To explore the scope of this reaction, a variety of
electron-rich and electron-deficient benzoic acid deriva-
tive substrates were also tested. Table 2 presents the
results for the activity of fullerene complex 1 in the deu-
teration reaction. Also, in control experiments, we mea-
sured the catalytic performance of Pd/C (10%) catalyst to
compare the effect of complexation of Pd core on FC60
nanoparticles with those of the traditional catalyst.
For the evaluation of deuterium incorporation in H/D
exchange reactions, we applied internal standard method.
In this procedure, the calculations are based on the 1 μl
of a compound which was added to the sample NMR
3.3 | Catalytic H/D exchange reaction
As noted in Section 1, one of the most commonly
employed methods for H/D exchange in aromatic sub-
strates is the catalytic H/D exchange reactions.[7a–d] As
part of our ongoing interest in the catalytic properties of
palladacyclopropa-[60]fullerene complexes,[13a–d] we
have now applied this type of complexes as a heteroge-
neous catalyst in the H/D exchange reaction of benzoic
acid derivatives. Moreover, this catalytic system was com-
pared with a conventional heterogeneous catalyst, 10%
Pd on carbon, in the same H/D exchange reactions.
1
tube, having no overlap in HNMR spectrum of deuter-
ated sample, such as acetonitrile. This is a basic proce-
dure for quantitative NMR (qNMR) using the following
formula[23]
:
Ix Nstd
×
Mx mstd
× × Pstd
PX =
×
Istd Nx
Mstd mx
where I, N, M, m, and P are integral area, number of
nuclei, molar mass, gravimetric weight, and purity of
analyte (X, remained hydrogenated form in deuterated
compound) and standard (Std), respectively. Also, the
In a typical reaction, a catalytic amount of the com-
plex 1 (1 mol %) was added to benzoic acid in D2O, which
leads to extensive H/D exchange. Determination of
FIGURE 8 TEM images of complex 1

YOUSEFI ET AL.
9 of 12
TABLE 2 Deuteration of benzoic acid derivatives mediated by complex 1 and Pd/C (10%)
Entry
1 mol% complex 1
Entry
5 mol% Pd/C (10%)a
Yield (%)b
1
5
90 (95)
93 (97)
96 (95)
2
6
3
7
4
8
90 (91)
Note: D contents were determined by 1H NMR.
aCatalytic reactions using Pd/C (10%) catalyst were carried out in H2 gas (1 bar).
bIsolated yields in parenthesis are obtained with Pd/C (10%) catalyst.
incorporation of deuterium can be obtained by 100-PX,
which indicates the deuteration percentage in a particu-
lar position.
Similar calculations were also applied for meta posi-
tion of nitro group in 4-nitrobenzoic acid:
1
0:24
3
3
2
167:12 0:79
For example, based on the HNMR spectrum of deu-
PX =
×
×
×
× 100 PX = 1:61100−PX = 98:39
41:05
24
terated 4-nitrobenzoic acid (Figure 9), the incorporation
of deuterium in ortho position of nitro group in this sam-
ple (Table 2, entry 1) can be calculated as follows:
Deuteration percentage in a meta position of nitro group
in 4-nitrobenzoic acid = 98.39%.
0:22
3
3
2
167:12 0:79
Although complex 1 extensively catalyzed deuterium
incorporation into some activated and unactivated
benzoic acid derivative substrates, different deuteration
percentages were obtained. In the case of using complex
1 and benzoic acid derivatives as a catalyst and
PX =
×
×
×
× 100 PX = 1:47100−PX = 98:53
41:05
24
Deuteration percentage in an ortho position of nitro
group in 4-nitrobenzoic acid = 98.53%.

10 of 12
YOUSEFI ET AL.
FIGURE 9 1H NMR spectrum of deuterated 4-nitrobenzoic acid; sample weight: 24 mg, 1 μl acetonitrile internal standard weight:
0.79 mg
substrates, respectively, the incorporation of deuterium
atom on aromatic ring follows this order: (4-NO2)-
BzOH > (4-Br)BzOH > BzOH > (4-OMe)BzOH>
(Table 2, entries 1–4). However, using Pd/C (10%) as cata-
lyst apparently gave lower deuterium efficiency on the
aromatic ring in similar order (Table 2, entries 5–8). Sub-
stitution of the nitro group and bromine atom on aro-
matic ring reduces the C–H bond activation energy.
Hence, these electron-withdrawing substituents enhance
the H/D exchange reaction, and high levels of deutera-
tion (>95%) at all positions were obtained by using cata-
lyst 1 (Table 2, entries 2 and 3). Even using these
activated benzoic acid derivative substrates, Pd/C (10%)-
catalyzed reactions led to almost lower deuterium incor-
poration in Dα positions (Table 2, entries 6 and 7). Only
the methoxy group as an electron donating group of the
aromatic ring causes an increase in the C–H bond activa-
tion energy and reduces the H/D exchange efficiency
(Table 2, entries 4 and 8). Also, the methyl positions of
the methoxy group in 4-methoxybenzoic acid underwent
the deuteration with a comparatively less efficient D
incorporation. These observations are in accordance with
described substituent effects on aromatic nucleophilic
substitution reactions.[24]
in the second run, and it remained almost unchanged in
the next run. To find out what happened to that complex
after the first run, we focus on characterization of the cat-
alyst after catalytic reaction. Based on the 31P NMR
results obtained from catalytic system after the first run
and comparing with the 31P NMR data of phosphorus
ylide Y1 and complex 1, it seems that the catalytic cycle
begins with the dissociation of phosphorus ylide ligands
from the metal. Upon heating the reaction mixture to
100ꢀC, significant changes in the chemical shift of phos-
phorus ylide moiety were observed (see Supporting Infor-
mation). The peak at 24 ppm due to complex 1 was
eliminated in 31P NMR spectra of the reaction mixture
after the first catalytic run and the sharp peak at 14 ppm
due to free phosphorus ylide beside a weak singlet peak
at 26 ppm due to traces of triphenyl phosphine oxide that
appeared. This observation gives clear evidence that cata-
lyst 1 undergoes an irreversible phosphorus ylide ligands
dissociation during heating at the reflux temperature of
the catalytic reaction. It provides a large surface area for
chemisorption of substrates (benzoic acid derivative and
D2O) on nano-scaled FC60-based palladium heteroge-
neous catalyst and leads to high catalytic activity in com-
parison with conventional Pd/C catalyst.
The Pd/C catalyst could be recovered by simple filtra-
tion and reused for the second and third runs almost
without apparent decrease in its catalytic activity. How-
ever, the catalytic efficiency of filtered complex 1 reduced
However, the obtained large surface area loses its
high performance, and the observed high catalytic activ-
ity turns into moderate to low catalytic activity. The rea-
son for such a negative trend in the reusability of

YOUSEFI ET AL.
11 of 12
complex 1 could be explained by the fact that catalytic
active sites in the first run have been occupied by reac-
tants. Based on the known chemistry of palladium-FC60
complexes,[25a–c] reaction of Pd (dba)2 with FC60 in tolu-
ene solution leads to facile replacement of the dba ligand
by FC60 and formation of [C60Pd]n one-dimensional
insoluble polymer. Heating a suspension of [C60Pd]n one-
dimensional polymer in toluene at reflux temperature
increased the Pd/C60 ratio to 2:1 within a day to form
[C60Pd2]n two-dimensional polymer and then gradually
reached the ratio approximately 3:1 in several days to
form a [C60Pd3]n three-dimensional polymer.[25a] As the
catalytically active sites in monomeric C60Pd species
turned into one-, two-, and three-dimensional polymer
[C60Pdm]n (m = 1–3) during catalyst reuse tests, the
accessible surface area of Pd nanoparticles dropped sig-
nificantly, and poor catalyst reusability was achieved,
consequently. Considering these reasons, the suppression
of catalyst activity and the unsatisfactory reusability
results could be justified.
ORCID
Abed Yousefi https://orcid.org/0000-0003-4159-5840
Seyyed Javad Sabounchei https://orcid.org/0000-0001-
9000-5304
Ali Hashemi https://orcid.org/0000-0002-0831-8705
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DATA AVAILABILITY STATEMENT
The data that support the findings of this study are avail-
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AUTHOR CONTRIBUTIONS
Abed Yousefi: Conceptualization; data curation; formal
analysis; investigation; methodology; project administra-
tion; resources. Seyed Javad Sabounchei: Formal analy-
sis;
funding
acquisition;
investigation;
project
administration; supervision. Ali Hashemi: Formal
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Yousefi A,
Sabounchei SJ, Hashemi A. New Pd-phosphorus
ylide complexes based on FC60 as heterogeneous
nano-catalyst for H/D exchange reaction. Appl
Organomet Chem. 2021;35:e6139. https://doi.org/
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