RSC Advances
Paper
Acknowledgements
The authors are extremely thankful to Professor B. K. Mishra,
Director, IMMT, Bhubaneswar 751013, Odisha, India, for his
constant encouragement and permission to publish this work.
GBBV and SKR are obliged to CSIR for a senior research
fellowship.
Notes and references
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improving the stability of the metal duo, due to the strong
interactions of the metals with the support surface via the
amine functionality. Eight test recycles were performed to
evaluate the reusability of 5 wt% Cu, Ni NH2-MMT, as shown
in Fig. 15. The catalyst still retained high catalytic performance
similar to that of the fresh catalyst after several recycles; no
decrease in catalytic activity was observed after six uses.
Fig. 16 shows the FTIR spectra of the reused catalyst.
Although the peaks are lower in intensity, the proximity of all
the peaks to those of the original sample strongly support the
stability of the catalyst.
The primary role of amine functionalization can only be
recognized by carrying out the reaction on 5 wt% Cu, Ni MMT.
Though almost the same results were observed i.e. 98%
product yield under the same reaction conditions as for 5 wt%
Cu, Ni NH2-MMT, traces of Cu and Ni could be detected in the
filtrate after the 2nd cycle, when subjected to AAS analysis.
There was also a significant (10%) decrease in the yield
obtained in the 3rd cycle. These results confirm that the amine
groups on the surface of MMT are good binders with respect to
Cu, Ni NH2-MMT.
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Conclusions
The easy to prepare, cheap and stable mixed metal catalyst
system reported here shows ultra-high catalytic activity for the
C–S coupling reaction. The effectiveness of having both copper
and nickel present in the reaction can be rationalized by
carrying out the reaction with the monometallic catalysts. This
catalytic procedure offers general applicability and simplicity,
avoiding expensive and time consuming protocols. The
development of other stable bimetallic (transition metal)
nano-catalysts dispersed over the same support, in order to
avoid costly noble metal catalyzed reactions in favour of more
cost effective ones is a future research prospect for our group.
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This journal is ß The Royal Society of Chemistry 2013
RSC Adv., 2013, 3, 7570–7578 | 7577