CRYSTAL AND MOLECULAR-STRUCTURE OF I-MU-BROMOBROMOPENTAKIS(BENZIMIDAZOLE)DICOPPER(II) MONOBROMIDE TETRAHYDRATE [CU2BR3(C7H6N2)5]BR-CENTER-DOT-4H2O

A new complex compound, [Cu2Br3(C7H6N2)5]Br.4H2O, has been synthesized and its crystal structure investigated by single-crystal X-ray method s. The crystals are isostructural with those of the [Cu2Cl3(C7H6N2)5]C l . 4H2O salt. They are orthorombic, space group Pnma with 4 formula u nits in a cell of dimensions: a = 19.923(1), b = 17.555(2), c = 12.052 3(4)angstrom. The structure was refined by full-matrix least-squares t o give R = 0.047 and R(w) = 0.053 for 3569 intensities above 3sigma(I) . As in the chloride compound, the complex cation consists of pairs of distorted trigonal bipyramidal Cu(II) centers which share an edge by two equatorial bromide ions. The Cu...Cu nonbonding distance in the co mplex is 3.4894(7)angstrom. The two Cu-Br-Cu bridges are not equivalen t and their geometry is slightly different from that in the chloride c omplex. Comparison of the investigated structure to other binuclear bi s(mu-halide) bridged copper(II) complexes of similar structure has bee n made.