Few-layered graphene-supported 1.1.1 and 2.0.0 oriented Au and Cu2O nanoplatelets were prepared by one-step pyrolysis of the corresponding metal salts embedded in chitosan at 900 C under inert atmosphere. These nanometric films containing oriented nanoplatelets were investigated in a series of reactions as Ullmann-type homocoupling, C-N cross-coupling and Michael addition. The catalysts exhibited turnover numbers (TONs) three to six orders of magnitude higher than those of analogous graphene-supported unoriented metal nanoparticles. In addition it has been found that oriented Cu2O and Au nanoplatelets grafted on defective graphene also exhibit activity to promote the Michael addition of compounds with active methylene and methine hydrogens to conjugated ketone. An exhaustive characterization of these materials using spectroscopic and electron microscopy analyses has been carried out. CO2 thermoprogrammed desorption measurements show that films of these two graphene supported catalysts exhibit some basicity that can explain their activity to promote Michael addition.
Michael and Henry addition reactions have been investigated using mono (Au and Cu2O) and bimetallic nanoplatelets (Au/Cu2O) grafted onto few‐layers graphene (fl‐G) films as heterogeneous catalysts by comparison with homogeneous NaOH and K2CO3 ones. In the presence of the heterogeneous catalysts, these reactions occurred in the absence of any extrinsic (NaOH and K2CO3) base with turnover numbers (TONs) at least four orders of magnitude higher. While the homogeneous catalysts provided TONs close to the unity for Au/Cu2O/fl‐G this was of the order of 107. These reactions also occurred with a very good selectivity to the targeted products. These performances are in line with the basicity of these catalysts demonstrated from CO2 chemisorption measurements. The effect of the nanosize and the interaction of the nanoparticles with the graphene are also important to achieve this high activity.
The compounds [2‐(Me2NCH2)C6H4]2SbL (L = ONO2 (2), OSO2CF3 (3)) and [PhCH2N(CH2C6H4)2]SbL (L = ONO2 (5), OSO2CF3 (6)) were prepared by reacting [2‐(Me2NCH2)C6H4]2SbCl (1) and [PhCH2N(CH2C6H4)2]SbCl (4), respectively, with the appropriate silver(I) salt in a 1:1 molar ratio. The new species 2–6 were structurally characterized in solution using multinuclear NMR and in the solid state using infrared spectroscopy. The solid‐state structures for compounds 2, 4 and 6, as well as for the hydrolysis ionic product [{2‐(Me2N+HCH2)C6H4}{2‐(Me2NCH2)C6H4}SbOH][CF3SO3]− (3h) were determined using single‐crystal X‐ray diffraction. Medium to strong intramolecular N→ Sb interactions were observed in all these four compounds, thus resulting in hypercoordinated organoantimony(III) species 14‐Sb‐6 in 2 and 10‐Sb‐4 in the cation of 3h and in 4 and 6. Compounds 1–6 and the starting amines PhCH2NMe2 and PhCH2N(CH2C6H4Br‐2)2 were investigated as catalysts in the Henry (nitroaldol) addition of nitromethane to benzaldehyde. The activity of compounds 1–6 resulted as an effect of the cooperation of the positively charged antimony with the negatively charged nitrogen.
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