Synthesis and Structural Characterization of an Unprecedented Nonmetal Cation Polyborate Salt Containing Two Different Isolated Polyborate Anions: [H2en]2[B4O5(OH)4][B7O9(OH)5]•3H2O (en = H2NCH2CH2NH2)

The nonmetal cation polyborate salt of stoichiometry [H(2)en](2)[B11O18(OH)]center dot 7H(2)O is obtained from the reaction of 1,2-diaminoethane and boric acid (1:5 ratio) in H2O/MeOH. An X-ray crystallographic study of the product reveals that the polyborate moiety is composed of two isolated hydrated polyborate anions: [B4O5(OH)(4)](2-) and [B7O9(OH)(5)](2-). The structure is templated by the cations with the anions forming a supramolecular H-bonded network, augmented by additional H-bonds involving the waters of crystallization and the cations.