Reaction of 9-bromo-9,10-dihydro-9-silaphenanthrene (6) with lithium diisopropylamide (LDA) in THF at room temperature afforded kinetically stabilized 9-silaphenanthrene la bearing an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). 9-Silaphenanthrene la was isolated as pale yellow crystals, and the structure of la was completely determined by spectroscopic and X-ray crystallographic analyses. The 1H and 13C NMR chemical shifts corresponding to the 9-silaphenanthrene ring of la were observed in a typical aromatic region, while the central silicon atom showed the characteristic signal at 86.9 ppm in the 29Si NMR in C6D6. The 9-silaphenanthrene ring of la showed completely planar geometry, indicating that 9-silaphenanthrene has a delocalized 14π-electron system as an aromatic compound. In spite of its high thermal stability, la still has high reactivity at the 9,10position toward small reagents such as H2O.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry