PREPARATION OF MONONITROPENTAHYDROHEXABOR ATE(2-) AND CRYSTAL-STRUCTURE OF M(2)[B6H5(NO2)], M=K, CS

By electrochemical oxidation of [B6H6](2-) in the presence of nitrite ions and the base DBU in dichloromethane solution mononitropentahydroh exaborate [B6H5(NO2)](2-)ions are formed and can be isolated by ion ex change chromatography on diethylaminoethyl cellulose. The crystal stru ctures of the K and Cs salt were determined from single crystal X-ray diffraction analyses. K-2[B6H5(NO2)] is monoclinic, space group P2(1)/ m with a = 5.953(1), b = 8.059(4), c = 8.906(1) Angstrom, beta = 109.5 53(9)degrees; Cs-2[B6H5(NO2)] is monoclinic, space group P2(1)/a with a = 9.438(6), b = 9.644(7), c = 11.138(9) Angstrom, beta = 101.44(9)de grees. The B-6 octahedron is compressed in the direction of the B-NO2, bond by about 5%, with bond lengths between 1.67 and 1.77