Neue Acetylide - Synthesen, Strukturen, Eigenschaften

Taking into account the methods used to prepare alkali metal chalcogenides of the type AA'X (X = O2-, S2-, Se2-, Te2-) a new route of preparation was found for alkali metal acetylides (X = C2-). With this approach the unknown compounds cesium sodium, cesium potassium, cesium rubidium and potassium rubidium acetylide were obtained. By means of synchrotron powder diffraction data and the application of structure solution methods such as the charge flipping algorithm, or by comparison with similar compounds, the orthorhombic and tetragonal structures of CsNaC2, CsKC2 and CsRbC2 were identified and refined by Rietveld methods. Their temperature-dependent structural behaviour was investigated by DSC measurements and by in situ high temperature synchrotron diffraction data. Due to the thermally stimulated motion of the acetylide dumbbell various structural transformations were observed. A novel disorder was discussed in the case of cesium sodium acetylide.

These results were summarised with regard to analogous structures of the same class of compounds. Similarities and differences were illuminated by integrating all structures into the structural classification of alkali metal chalcogenides. Additionally, attempts to generalize this structural classification were made focusing on cationic and anionic structural motives.

The formation of solid solutions in quaternary alkali metal palladium acetylides was exemplarily demonstrated in case of potassium rubidium palladium acetylide. By Rietveld refinements of the corresponding X-ray powder diffaction patterns a behaviour obeying Vegard's rule was observed.

The uninvestigated solubility of alkali metal acetylides in liquid ammonia was demonstrated in cooperation with M. Hamberger, a member of the group of Prof. Dr. N. Korber in Regensburg. At low temperatures new single crystalline compounds were obtained. Details of these structures were highlighted and their perspectives were discussed in comparison to the already known alkali metal acetylides.