P NANOPARTICLES · P4 as precursor for metal phosphide nanoparticles and N2 activation and reduction to organic derivatives

P4 as precursor for metal phosphide nanoparticles and N2 activation and reduction to organic derivatives

Two different topics were studied during the two years of the project. The first one involved the use of white phosphorus P4 as a stoichiometric P atom donor for the synthesis of nanocristals of metal-phosphides MxPy. The second topic dealt with the activation of dinitrogen. These projects may appear unrelated, but in fact in the strategy envisioned, they do both rely on the use of transition metals in a reduced form. Two metal phosphides were selected for the first part of the project: Ni2P and InP. Indeed, these two compounds are of primary importance, as Ni2P is an industrial catalyst for the hydrodesulfuration of crude oil, and InP is a semiconductor. It has been shown that nanocristals of semi-conductors possess luminescent properties that depend: a) on the chemical elements; b) on the size of the nanocristal; c) on the shape of the nanocristal; and d) the efficient trapping of the electron / hole pair in the nanocristal. Our purpose was to design the appropriate chemical systems and to understand the mechanisms by which the desired MxPy could be formed. In a preliminary work, we had shown that either monometallic Ni(0) precursor or Ni(0) nanoparticles would be used to generate the corresponding Ni2P upon reaction with stoichiometric amounts of white phosphorus. This work opened the way for the extension of this strategy to In(0) precursors. The In(0) nanoparticles could be generated from the air and water sensitive In(I) precursor, Cp*In (Cp* = pentamethyl cyclopentadienyl). The formation of nanoparticles of InP with excellent dispersion in size could be achieved. The luminescent properties of these nanocristals were not satisfactory since nanoparticles of InP are known to oxidize rapidly in air. The second part of the project dealt with the activation of dinitrogen N2, as well as its functionalisation into amines of the type NR3. This task is of major importance as amines are industrially synthesised from NH3, which is in turn synthesised from N2 under strenuous conditions (Haber Bosch process, heterogeneous catalysis). We have based our work on known Mo(0) complexes which feature N2 as ligand. We focused on the use of Mo(dppe)2(N2)2 to evaluate the possible involvement of radical species R° to generate NR3. R° were chosen as bulky silyl derivatives R'3Si°.

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