Charged Si-9 Clusters in Neat Solids and the Detection of [H2Si9](2-) in Solution: A Combined NMR, Raman, Mass Spectrometric, and Quantum Chemical Investigation

摘要

Polyanionic silicon clusters are provided by the Zintl phases K4Si4, comprising [Si-4](4-) units, and K12Si17, consisting of [Si-4](4-) and [Si-9](4-) clusters. A combination of solid-state MAS-NMR, solution NMR, and Raman spectroscopy, electrospray ionization mass spectrometry, and quantum-chemical investigations was used to investigate four- and nine-atomic silicon Zintl clusters in neat solids and solution. The results were compared to Si-29 isotope-enriched samples. Si-29-MAS NMR and Raman shifts of the phase-pure solids K4Si4 and K12Si17 were interpreted by quantum-chemical calculations. Extraction of [Si-9](4-) clusters from K12Si17 with liquid ammonia/222crypt and their transfer to pyridine yields in a red solid containing Si-9 clusters. This compound was characterized by elemental and EDX analyses and Si-29-MAS NMR and Raman spectroscopy. Charged Si-9 clusters were detected by Si-29 NMR in solution. Si-29 and H-1 NMR spectra reveal the presence of the [H2Si9](2-) cluster anion in solution.