An Efficient Multi-Gram Access in a Two-step Synthesis to Soluble Nine-atomic Silylated Silicon Clusters

Silicon is by far the most important semiconducting material. However, solution-based synthetic approaches for unsaturated silicon-rich molecules require less efficient multi-step syntheses. We report on a straightforward access to soluble, polyhedral Si 9 clusters from the binary phase K 12 Si 17 , which contains both [Si 4 ] 4- and [Si 9 ] 4- clusters. [Si 4 ] 4- ions, characterised by a high charge per atom ratio, behave as strong reducing agents, preventing [Si 9 ] 4- from directed reactions. By the here reported separation of [Si 4 ] 4- , Si 9 clusters are isolated as monoprotonated [Si 9 H] 3- ions on a multi-gram scale and further crystallised as their 2.2.2 Cryptate salt. 20 grams of the product can be obtained through this two-step procedure - a new starting point for silicon Zintl chemistry such as the first isolation and structural characterisation of a trisilylated [ Me Hyp 3 Si 9 ] - cluster.