Project Details
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Polysilicides and their Transition Metal Complexes: Synthesis and Structure Elucidation in Liquid Ammonia and in Solid Ammoniates

Subject Area Solid State and Surface Chemistry, Material Synthesis
Term from 2017 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 388504559
 
Final Report Year 2023

Final Report Abstract

Silicon is the central element of semiconductor technology, which in turn is at the heart of the digital transformation encompassing all areas of human activities. The chemistry of this element is accordingly well studied, but it is precisely at the interface between the solid state, which is the basis for semiconductor technology, and the states of silicon and its compounds in the gas phase and in solution that there is still considerable need for research and potential for innovation. The project focused on polysilicides, a special class of molecular anions consisting only of silicon atoms. These are known in the solid state, but it was only relatively late that they could also be transferred to solutions in liquid ammonia, and the two project leaders were able to detect them in these solutions for the first time using NMR spectroscopy in preparatory work. Solution chemistry is at the heart of most chemical transformations, so the exploration and exploitation of these dissolved polysilicides was the subject of investigation. Through the collaboration of a group specializing in chemistry in liquid ammonia and a group with great expertise in the field of NMR spectroscopy, a wealth of polysilicides in solution could be generated and characterized in more detail. Of particular note is the first-time detection of [Si5]2− in solution and the studies on [HSi9]3−. While the former polysilicide is a rigid cage in the shape of a trigonal bipyramid, [HSi9]3− was spectroscopically shown to be highly flexible. The reactivity of this species was investigated mainly toward complexes of the transition metals, and [HSi9]3− could be bound to the element copper. A number of the species found in solution could subsequently also be crystallized out in the form of ammoniates, ammonia-rich solid-state compounds, and characterized by means of X-ray structural analysis.

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