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Johnson Matthey Technol. Rev., 2015, 59, (2), 120

doi:10.1595/205651315x687407

In the Lab: Ductile Metal Oxides Impregnated on Magnetite: New Catalysts in Organic Synthesis

Johnson Matthey Technology Review features new laboratory research

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Diego J. Ramón is a Professor in the Department of Organic Chemistry at the University of Alicante, Spain. His research focuses on the development of catalysts based on transition metal oxides impregnated on the surface of magnetite and their application to different reactions of general interest in Organic Chemistry. He has published over 100 papers.

About the Researcher

  • Name: Diego J. Ramón

  • Position: Professor

  • Department: Organic Chemistry

  • University: University of Alicante

  • Street: Carretera San Vicente del Raspeig s/n

  • City: Alicante

  • Post Code: E-03080

  • Country: Spain

  • Email Address: djramon@ua.es

About the Research

The particle size of active material in heterogeneous catalysts has a great impact on selectivity, efficiency and specificity. In fact, nano-catalysts have properties different from the macroscopic systems due not only to different specific area but also to the presence of electric charges over them, and above all to the presence of extremely distorted bonds.

Metallic oxides, including magnesia, alumina, silica, zirconium oxide and cerium oxide, are supports commonly used in the preparation of nano-metal catalysts. Although magnetite (Fe3O4), like any other metal oxide, could be used as a suitable support, as has been demonstrated in other areas including medicine, biology and materials science, its use in organic chemistry has been minimal, due to the axiomatic idea that magnetite is unstable. As a support, magnetite has a unique advantage due to the superparamagnetic behaviour of its nanoparticles that allows its recovery and confinement by using a simple magnet or electromagnetic field. This property should make magnetite an ideal support material.

Ramón's group has designed a simple, robust and inexpensive methodology for the impregnation of different transition metal oxides on the surface of magnetite. The impregnation protocol allows all active nano-metallic species to be on the surface of the catalyst, and therefore increases their activity. The group has prepared catalysts derived from cobalt, copper, ruthenium, palladium, osmium, iridium and platinum (Figure 1). These versatile catalysts have been used to carry out several transformations of general interest in organic chemistry (Figure 2), among others Suzuki-Miyaura cross-coupling, the multicomponent reductive amination of aldehydes, hydrosilylation of alkynes, borylation of olefins, benzofurans and indole synthesis, and the alkylation of amines through a borrowing hydrogen strategy. Moreover it has been possible to achieve the first practical cross-alkylation of primary alcohols using iridium impregnated on magnetite.

Fig. 1.

Transmission electron microscopy (TEM) images of magnetite-derived catalysts: (a) copper; (b) ruthenium; (c) palladium; and (d) iridium

Transmission electron microscopy (TEM) images of magnetite-derived catalysts: (a) copper; (b) ruthenium; (c) palladium; and (d) iridium

Fig. 2.

Application of magnetite and transition metal oxides impregnated on magnetite to different organic synthesis reactions

Application of magnetite and transition metal oxides impregnated on magnetite to different organic synthesis reactions

When an external magnetic field is applied, the superparamagnetic particles of the magnetite acquire magnetisation, but it is lost when the magnetic field is retired. So, magnetite nanoparticles can be isolated easily from the reaction media using an external magnet (Figure 3) after the reaction. In many cases, the catalyst could be recovered by the simple use of a magnet and recycled in successive cycles with the same initial activity. Figure 4 shows the yields obtained with the different catalysts in ten successive reaction cycles.

Fig. 3.

Easy recovery of the catalyst after reaction by using a magnet

Easy recovery of the catalyst after reaction by using a magnet

Fig. 4.

Obtained yields in selected reactions after recycling different catalysts

Obtained yields in selected reactions after recycling different catalysts

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Selected Publications

  1.  J. M. Pérez and D. J. Ramón, Adv. Synth. Catal., 2014, 356, (14–15), 3039 LINK http://dx.doi.org/10.1002/adsc.201400207
  2.  J. M. Pérez, R. Cano and D. J. Ramón, RSC Adv., 2014, 4, (46), 23943 LINK http://dx.doi.org/10.1039/C4RA03149K
  3.  R. Cano, J. M. Pérez and D. J. Ramón, Appl. Catal. A: Gen., 2014, 470, 177 LINK http://dx.doi.org/10.1016/j.apcata.2013.10.050
  4.  R. Cano, M. Yus and D. J. Ramón, Tetrahedron, 2013, 69, (34), 7056 LINK http://dx.doi.org/10.1016/j.tet.2013.06.041
  5.  J. M. Pérez, R. Cano, M. Yus and D. J. Ramón, Synthesis, 2013, 45, (10), 1373 LINK http://dx.doi.org/10.1055/s-0032-1316872
  6.  J. M. Pérez, R. Cano, M. Yus and D. J. Ramón, Eur. J. Org. Chem., 2012, (24), 4548 LINK http://dx.doi.org/10.1002/ejoc.201200319
  7.  R. Cano, M. Yus and D. J. Ramón, Chem. Commun., 2012, 48, (61), 7628 LINK http://dx.doi.org/10.1039/c2cc33101b
  8.  R. Cano, M. Yus and D. J. Ramón, ACS Catal., 2012, 2, (6), 1070 LINK http://dx.doi.org/10.1021/cs300056e
  9.  R. Cano, M. Yus and D. J. Ramón, Tetrahedron, 2012, 68, (5), 1393 LINK http://dx.doi.org/10.1016/j.tet.2011.12.042
  10.  R. Cano, M. Yus and D. J. Ramón, Tetrahedron, 2011, 67, (42), 8079 LINK http://dx.doi.org/10.1016/j.tet.2011.08.063
  11.  R. Cano, D. J. Ramón and M. Yus, Synlett, 2011, (14), 2017 LINK http://dx.doi.org/10.1055/s-0030-1261162
  12.  R. Cano, D. J. Ramón and M. Yus, J. Org. Chem., 2011, 76, (14), 5547 LINK http://dx.doi.org/10.1021/jo200559h
  13.  R. Cano, D. J. Ramón and M. Yus, Tetrahedron, 2011, 67, (30), 5432 LINK http://dx.doi.org/10.1016/j.tet.2011.05.072
  14.  R. Cano, D. J. Ramón and M. Yus, J. Org. Chem., 2010, 75, (10), 3458 LINK http://dx.doi.org/10.1021/jo100325e
  15.  M. J. Aliaga, D. J. Ramón and M. Yus, Org. Biomol. Chem., 2010, 8, (1), 43 LINK http://dx.doi.org/10.1039/b917923b
  16.  R. Martínez, D. J. Ramón and M. Yus, Adv. Synth. Catal., 2008, 350, (9), 1235 LINK http://dx.doi.org/10.1002/adsc.200800089
 

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