A magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdII nanocomposite exhibiting facile tandem Suzuki coupling/transfer hydrogenation reaction
Parminder Singh, Saumyaranjan Mishra, Anupam Sahoo, Srikanta Patra
Abstract
Abstract Herein, we report a magnetically retrievable mixed-valent Fe 3 O 4 @SiO 2 /Pd 0 /Pd II NP ( 5 ) nanocomposite system for tandem Suzuki coupling/transfer hydrogenation reaction. The nanocomposite 5 was prepared first by making a layer of $$\hbox {SiO}_{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mtext>SiO</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:math> on $$\hbox {Fe}_{3}\hbox {O}_{4}\hbox {NP}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Fe</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>4</mml:mn></mml:msub><mml:mtext>NP</mml:mtext></mml:mrow></mml:math> followed by deposition of $$\hbox {Pd}^{0}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mtext>Pd</mml:mtext><mml:mn>0</mml:mn></mml:msup></mml:math> and sorption of $$\hbox {Pd}^{\mathrm{II}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mtext>Pd</mml:mtext><mml:mi>II</mml:mi></mml:msup></mml:math> ions successively onto the surface of Fe 3 O 4 @SiO 2 NP. The nanocomposite was characterized by powder XRD, electron microscopy (SEM-EDS and TEM-EDS) and XPS spectroscopy techniques. The mixed-valent $$\hbox {Pd}^{0}/\hbox {Pd}^{\mathrm{II}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>Pd</mml:mtext><mml:mn>0</mml:mn></mml:msup><mml:mo>/</mml:mo><mml:msup><mml:mtext>Pd</mml:mtext><mml:mi>II</mml:mi></mml:msup></mml:mrow></mml:math> present onto the surface of nanocomposite 5 was confirmed by XPS technique. Interestingly, the mixed-valent nanocomposite Fe 3 O 4 @SiO 2 /Pd 0 /Pd II NP ( 5 ) exhibited tandem Suzuki coupling/transfer hydrogenation reaction during the reaction of aryl bromide with aryl boronic acid (90% of C ). The nanocomposite 5 displayed much better reactivity as compared to the monovalent Fe 3 O 4 @SiO 2 /Pd 0 NP ( 3 ) (25% of C ) and Fe 3 O 4 @SiO 2 /Pd II NP ( 4 ) (15% of C ) nanocomposites. Further, because of the presence of magnetic $$\hbox {Fe}_{3}\hbox {O}_{4}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Fe</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math> , the nanocomposite displayed its facile separation from the reaction mixture and reused at least for five catalytic cycles.