The zwitterionic spirocyclic h5-silicates bis [3,4,5,6-tetrabromol CH,CN, and 4 were characterized by solid-state NMR spectroscopy ("Si and 15N CP/MAS). The pentacoordinate silicon atoms of 5,5 . H 2 0 (two crystallographically independent zwitterions and two crystallographically independent water molecules), and 6 (two crystallographically independent zwitterions) are surrounded by four oxygen atoms and one carbon atom. The coordination polyhedrons around the silicon atoms of 5 and 6 can be described as distorted (5) or nearly ideal (6) trigonal bipyramids, the carbon atoms being in equatorial positions. 5 forms intramolecular and 6 intermolecular (-+ for-