Reactive Gas Pressure Synthesis

The development of a special equipment for synthesis and handling of samples under high-purity conditions and protective atmosphere is closely related to the general progress made in the area of solid state chemistry. From this point of view nitride-diazenides and hydrido-platinates represent fundamental examples of compounds which are available by reactive gas pressure methods. The parameter gas pressure is a crucial tool for selective syntheses by adjusting the redox-potential of the reaction gas by varying its pressure.

Figure 1. Schematic sketch of the high-pressure device for reactive gas pressure syntheses.

The device for reactive gas pressure syntheses includes high-pressure autoclaves made from Inconel, which are sealed with copper gaskets. The reaction pressure is measured and registered during the synthesis. High-pressures are obtained by using the following procedure: The high-pressure autoclave is cooled down with liquid nitrogen and the reaction gas (N₂, H₂, D₂, Ar) or a gas mixture is condensed from gas bottles and/or medium reaction vessels, respectively, into the autoclave (all autoclaves are connected in series). This technique facilitates access to reaction pressures within the autoclave up to a desired value taking into account all necessary aspects of safety. The reaction volume of the autoclave is about 14 cm³. The maximum value of the reaction temperature strictly depends on the reaction pressure and should not exceed (p_max 6000 bar (T<925 K)/T_max 1100 K (p<500 bar)).

Figure 2. Photograph of the high-pressure device for reactive gas pressure syntheses.

Using this method numerous nitride-diazenides and hydridometalates/hydrides were synthesized by starting from the elements.

Figure 3. Controlled formation of intermediate phases gained by adjusted gas pressure in the strontium-nitride-diazenide pressure series.

References:

[1] W. Bronger, G. Auffermann, Chem. Mat., 10 (1998) 2723
[2] G. Auffermann, Yu. Prots, R. Kniep, Angew. Chem., 113 (2001) 545, Angew. Chem. Int. Ed., 40 (2001) 565
[3] Yu. Prots, G. Auffermann, M. Tovar, R. Kniep, Angew. Chem., 114 (2002) 2392; Angew. Chem. Int. Ed., 41 (2002) 2288
[4] G. Auffermann, R. Kniep, W. Bronger, Z. Anorg. Allg. Chem., 632 (2006) 565
[5] E. Horvath-Bordon, R. Riedel, A. Zerr, P. F. McMillan, G. Auffermann, Yu. Prots, W. Bronger, R. Kniep, P. Kroll, Chem.Soc. Rev., 35 (2006) 987