The Design of Molecular Complexes

One of the strategies to design nanodivided electrocatalyst is the use of chemical precursors, which can react nnder mild condi- 

This kind of chemical route led to the generation of transition-metal complexes. The base stmcture of such complexes can be the basis to obtain the so-called metaUic cluster-like materials. In this way, for example, chemical precursors were furnished by the complex developed by Adams et al. Indeed, these authors reported that Pt2Ru4(CO)ig (see Fig. 3) was obtained by reacting Ru(CO)s and Pt(cyclo-octadiene)2. The evolution of Pt2Ru4(CO)ig and the carbide PtRu5C(CO)ie to generate a bimetalhc catalyst (Pt-Ru) supported onto carbon substrate was later pubhshed by Nuzzo et al.  

One can imagine that the Pt2Ru4(CO)ig cluster compound is the intermediate in the reaction (2). The reaction can be further made via chemical decomposition of the compound to generate the bimetallic nanocatalyst. Indeed, Nuzzo et al. demonstrated that mixed Pt-Ru nanoparticles, with an extremely narrow size distribution (particle size 1.4 ran), were obtained. The Pt-Pt, Pt-Ru, and Ru-Ru coordination distances in the precursor (2.66, 2.64, and 2.84 A) changed to 2.73, 2.70, and 2.66 A, respectively, on the mixed-metal nanoparticles supported onto carbon black, with an enhanced crystalline disorder, as revealed by X-ray absorption fine stmcture (XAFS) spectroscopy. However, this example, using a controlled pyrolysis onto a designed molecirlar cluster, succeeds 

In order to understand the growth of metal clusters in solution, one should start from a metal complex precursor, such as [My(CO)x], according to Eq. (1). The precursor can be generated in situ. The protocol synthesis of such a chemical precursor is represented by the flow-chart see Fig. 4 for the case of ruthenium-selenide. This flow chart summarizes the synthesis initially reported in 1991, and it will be taken as the template for similar compounds. A careful follow-up of the reaction was made by means of the Indeed, following the synthesis without carbon, i.e., after step 3, a heteronuclear chemical precursor was identified Ru4Se2(CO)3(CO)g. The ongoing reaction under the boiling point of the solvent for 20 hours led to a complete pyrolysis of the heteronuclear molecular cluster compound to nanopowders of 

This later position corresponds to the mtheninm maximum diffraction peak as shown by the XRD pattern in Fig. 7. We observed that, on the one hand, an interesting fact is that this pyrolysis in gas phase resembles the XRD results published years before for RuxSCy nanopowders synthesized after 20 h in a non-aqueous solvent, i.e., xylene or 1,2-dichlorobenzene.  

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