Highly Active, Selective, and Reusable RuO<sub>2</sub>/SWCNT Catalyst for Heck Olefination of Aryl Halides
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Abstract
Very
fine RuO<sub>2</sub> nanoparticles (RuO<sub>2</sub>NPs) with
a mean diameter of about 0.9 nm were decorated on single-walled carbon
nanotubes (SWCNTs) by a straightforward “dry synthesis”
method. TEM images and the Raman spectrum of the resultant material
(RuO<sub>2</sub>/SWCNT) revealed excellent adhesion and homogeneous
dispersion of the RuO<sub>2</sub>NPs on anchoring sites of the SWCNTs.
The surface area of RuO<sub>2</sub>/SWCNT was found to be 416 m<sup>2</sup> g<sup>–1</sup>. The SEM–EDS results showed
that the weight percentage of Ru in RuO<sub>2</sub>/SWCNT was 13.8%.
The oxidation state of Ru in RuO<sub>2</sub>/SWCNT was +4, as confirmed
by XPS and XRD analyses. After the complete characterization, a 0.9
mol % loading of RuO<sub>2</sub>/SWCNT was used as a nanocatalyst
for the Heck olefination of a wide range of aryl halides to yield
products in excellent yields with good turnover numbers and turnover
frequencies. Less reactive bromo- and chloroarenes were also used
for the formation of coupled products in good yields. RuO<sub>2</sub>/SWCNT is regioselective, chemoselective, heterogeneous in nature,
and reusable. The stability of RuO<sub>2</sub>/SWCNT was also studied
by means of TEM, ICP-MS, SEM–EDS, and XPS analyses