PREPARATION AND CRYSTAL-STRUCTURES OF DIPYRIDINIOMETHANE MONOHALOGENOHYDRO-CLOSO-DODECABORATES(2-), [(C5H5N)(2)CH2][B(12)H(11)X] X=CL,BR,I

[B12H12](2-) reacts with dihalogenomethanes CH(2)X(2) in presence of trifluoro acetic acid, yielding the monohalogenodo-decaborates [B(12)H(11)X](2-) (X = Cl, Br; I), which are separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from the starting compound and higher halogenated products. The X-ray structure determinations of [(C5H5N)(2)CH2][B12H11Cl]. 2(CH3)(2)SO (orthorhombic, space group Pnma, a = 17.351(6), b = 16.034(5), c = 9.659(2)Angstrom, Z = 4) and of the isotypic bromo and iodo compounds [(C5H5N)(2)CH2][B(12)H(11)X] (monoclinic, space group P2(1)/n, Z = 4; for X = Br:a = 7.339(2), b = 15.275(3), c = 16.761(4)Angstrom,beta = 96.80(2)degrees; for X = I: a = 7.4436(8), b = 15.3510(8), c = 16.9213(16)Angstrom, beta = 97.326(7)degrees) exhibit crystal lattices build up by columns of substituted boron clusters and angular dications [(C5H5N)(2)CH2](2+) Orientated along the shortest axis which are assembled to alternating layers.