Abstract: The crystal structure of a new polymorphic modification oftetrakis(pentafluorophenyl)diboroxane(C₆F₅)₂BOB(C₆F₅)₂was determined by X-ray single crystal structure analysis. A comparison of thecalculated crystal densities of the monoclinic and triclinic modifications at150 K suggests the metastability of the monoclinic modification. Molecules ofthe different polymorphic modifications have similar characteristics andconformations, while the polymorphism manifests itself primarily in differentcrystal packings.