PREPARATION, B-11 NMR AND VIBRATIONAL-SPECTRA OF CIS-DINITROTETRAHYDRO-CLOSO-HEXABORATE(2-), CIS-[B6H4(NO2)(2)](2-), AND THE CRYSTAL-STRUCTURE OF CIS-CS-2[B6H4(NO2)(2)]

By electrochemical oxidation of [B6H6](2-) in the presence of nitrite ions and of the base DBU in dichloromethane solution apart from [B6H5(NO2)](2-) and [B6H5(NO)B6H5](3-) the dinitro anion cis-[B6H4(NO2)(2)](2-) is formed and can be isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of the Cs salt has been determined from single crystal X-ray diffraction analyses. cis-Cs-2[B6H4(NO2)(2)] is tetragonal, space group P $($) over bar$$ 42(1)m with a = 10.0656(4), c = 11.0127(13) Angstrom. The B-11 NMR spectrum is consistent with a disubstituted octahedral B-6 cage with local C-2v symmetry. The IR and Raman spectra exhibit characteristic NO2, B-H and B-6, vibrations.