Solventless Silane Alcoholysis Catalyzed by Recoverable Dirhodium(II) Perfluorocarboxylates

We have developed a novel reaction protocol for the highly efficient and sustainable catalysis of the silane alcoholysis reaction. The catalysts of choice are dirhodium(II) perfluorocarboxylates bearing long perfluoroalkyl chains, which are easily prepared in one step from commercial precursors. Under optimized reaction conditions, these catalysts exhibit up to about 50 times higher activity and 100 times higher productivity than analogous dirhodium(II) complexes described in the prior art. Furthermore, the reaction can be run in a completely solventless fashion. Finally, heterogenization of these catalysts has been accomplished through a novel strategy based on fluorous chemistry. Indeed, perfluorinated catalysts of this kind are easily adsorbed on silica which has been previously functionalized at its surface with perfluoroalkyl chains. Use of such supported catalysts (bonded fluorous phase catalysts) allows an easy and almost complete catalyst separation and recycling with improved catalytic performance.     

Ignition of Aluminum Powders Under Different Experimental Conditions

This paper presents a brief review of experimental measurements of aluminum ignition temperature. Models used to describe aluminum ignition are also reviewed. It is shown that the current models cannot describe ignition of aluminum powders of different sizes and ignited under various experimental conditions. The paper further discusses properties of and phase changes occurring in the alumina scale existing on the surface of aluminum particles at different temperatures. Results of recent thermal analysis studies of aluminum powder oxidation are presented and it is shown that the stepwise oxidation of aluminum is caused by the sequence of polymorphic phase transitions occurring in the growing oxide film. Finally, the qualitative connection between the processes governing the oxidation of aluminum powders and the ignition of aluminum particles is made and an explanation for the experimentally observed wide range of aluminum ignition temperatures is suggested.     

Electrochemical production of heterogeneous nickel catalysts for organic hydrogenations

The electrochemical deposition of nickel on copper, tin, aluminium or nickel in N,N-dimethylformamide is described. The cathodic surface becomes catalytically active towards the addition of molecular hydrogen onto unsaturated organic compounds. The activity of the catalyst is influenced by the nature of the cathode: copper gives the highest reactivity, then, in order of decreasing activity, aluminium, tin and nickel. The behaviour of the catalytic surfaces obtained with copper cathodes is comparable to that of the group of Raney nickel catalysts.