Pd(0)-Arg-boehmite: As Reusable and Efficient Nanocatalyst in Suzuki and Heck Reactions
and electron-poor aryl halides reacted with acrylonitrile,
methyl acrylate and styrene efficiently to produce the cor-
responding coupled products in good to excellent yields.
Whereas, styrene has been coupled with aryl halides in
the presence of 20 mg (2.7 mol%) of Pd(0)-Arg-boehmite.
Therefore, these results revealed that this methodology is
effective for a wide range of alkenes and aryl halides.
Catalytic cycle for Heck reaction in the presence of
Pd(0)-Arg-boehmite was outlined in Scheme 5.
catalyst showed shorter reaction time and better yield than
other catalysts. Also Pd(0)-Arg-boehmite is comparable in
terms of price, non-toxicity, stability and easy separation
with other reported catalyst. In addition, the recovery and
recycleability of this catalyst is more rapid and easier than
the other catalysts. Also, a comparison of activity based
on turnover frequency (TOF) showed excellent results for
in Table 5, Pd(0)-Arg-boehmite was showed a high TOF
was indicate that Pd(0)-Arg-boehmite is more effective and
more efficient in compared to other catalysts. More impor-
tantly, in comparison with other catalysts, Pd(0)-Arg-boe-
hmite has been easily prepared using cheap and commer-
cially available materials in a short period of time.
3.4 Reusability of the Catalyst
The reusability of the catalysts is an important factor for
industrial applications. Therefore, the recovery and reus-
ability of Pd(0)-Arg-boehmite was investigated using the
reaction of iodobenzene with phenylboronic acid in the
presence of described catalyst (Table 5). After completion
of the reaction, the catalyst was recovered via centrifuga-
tion, washed with ethyl acetate to remove residual product
and the catalyst reused for next reactions for at least 6 times
without any significant loss of its catalytic activity or pal-
ladium leaching. Which clearly demonstrates the practical
recyclability of this catalyst.
4 Conclusions
In conclusion a novel and efficient heterogeneous catalyst
(Pd(0)-Arg-boehmite) was synthesized by direct support-
ting of Pd-arginine complex on boehmite nanoparticles
for the first time. This catalyst was characterized by XRD,
TGA, TEM, SEM, EDS and ICP-OES techniques. The
Pd(0)-Arg-boehmite exhibits an excellent catalytic activity,
high reusability and air- moisture stability for the Suzuki
and Heck reactions. This methodology is effective for a
wide range of aryl halide including Cl, Br and I. Also the
catalyst can be recovered and recycled over 6 times without
any significant loss of its activity or palladium leaching.
3.5 Catalyst Leaching Study
The amounts of palladium leaching in reaction mixture was
studied by checking the Pd loading amount before and after
recycling of the catalyst by ICP-OEIS technique. Based on
ICP-OEIS analysis, the amount of palladium in fresh cata-
lyst and the recycled catalyst after 6 times recycling is 1.35
and 1.28 mmol/g, respectively, which indicated that palla-
dium leaching of this catalyst is very low.
Acknowledgements Authors thank the research facilities of Ilam
University, Ilam, Iran, for financial support of this research project.
In order to perform hot filtration experiment, two reac-
tion of iodobenzene with PhB(OH)2 has been performed
under optimized reaction conditions. In the first reaction,
the biphenyl was obtained after 22 min (in the half time of
the reaction) in 64% yield. Simultaneously in second reac-
tion, the same reaction was repeated, but in the half time
of the reaction (after 22 min), the catalyst was removed
from the reaction mixture by filtration and the reaction
mixture was allowed to run for another 22 min. The yield
of reaction in this stage was 66%. These experiments con-
firmed that Pd(0)-Arg-boehmite are essential for comple-
tion of reaction and the leaching of palladium hasn’t been
occurred.
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3.6 Comparison of the Catalyst
In order to examine the efficiency of these procedures, we
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