tained from which 5 can be extracted with n-pentane under argon (yield 47%). The X-ray structure analysis ( Fig. I ; measurement at OOC) shows 5 to be a planar molecule (apart from the methyl groups) with approximate DZh symmetry.The observed bond lengths are in good agreement with the M NDO results for 1,3,5,7-tetraamino-2,6-diaza-s-indacene and also with the bond lengths found in the case of 1,3,5,7-tetra-tert-butyl-~-indacene.~'*~'~~ The dipolar resonance structure 12 illustrates the bonding situation in 5 . However, further investigations are necessary in order t o clarify whether 5 has a delocalized structure or whether a very rapid valence isomerization between two localized structures takes place.As an electron-rich n-electron system, 5 is a strong reducing agent and air-sensitive, even in the crystalline state. Solutions in hexane or T H F show traces of radicals (ESR signal). A radical cation salt has so far not been isolated. 5 can be oxidized to 2 in good yields with nitrosyl tetrafluoroborate. 5 and 2 show consistent cyclovoltammograms.