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

• Applicants: Professorin Dr. Ruth M. Gschwind; Professor Dr. Nikolaus Korber
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388504559

Polysilicides are negatively charged molecular ions that are built exclusively from atoms of the chemical element silicon. Silicon is the central element in semiconductor technology, silicon structures are generated from melts at very high temperatures or by likewise energy-demanding depositions from the gas phase. A solution chemistry for homoatomic silicon building blocks such as polysilicides exists only rudimentarily. Polysilicides can be generated by solid state syntheses in compounds with alkali metal counter-ions. For the heavier elements germanium, tin and lead from the same chemical group, a solution chemistry of analogues compounds has been established for some time past. With the homoatomic building blocks of these elements, new element structures and new chemical compounds with transition metals could be prepared by a directed approach. The comparable polysilicides were thought to be insoluble for a long time. Only ten years ago it could be shown that liquid ammonia, a gas condensed at low temperatures, is able to dissolve a certain type of alkali metal polysilicides to a small extent. On the precise composition of these solutions is little known, the best analytical method in this case is NMR spectroscopy. The applicants could report on the first NMR-Signal of a polysilicide in 2013. In the project we propose to study systematically which polysilicides exist in liquid ammonia under which conditions. Relevant for this are further NMR investigations of the solutions, but also X-ray investigations on the ammoniates which crystalize from the solutions. Again, little is known on chemical reactions with dissolved polysilicides. In the project, we propose to react these elemental building blocks with transition metal compounds which have already yielded interesting new compounds with the heavier homologs germanium, tin and lead. The long term goal of the proposed project is to establish a solution chemistry of polysilicides.

• DFG Programme: Research Grants