PENTADECACOPPER(II) BISDIBORATE HEXAORTHOBORATE DIOXIDEis the only structure in which the isolated anions B2 O4-, BO]-and 0 2-are found together. ment with the diamagnetism observed for ReP a. The structure can be described as a stacking of identical layers of puckered pentagons and hexagons. In this way it is closely related to the structures of many compounds with compositions TX 2 and TX 4 (X = P, As, Sb, S, Se).