The First Borosulfate K₅[B(SO₄)₄]

The first of its kind: K5[B(SO4)4], the first example of a borosulfate, comprises non-condensed [B(SO4)4]5− anions in which the boron atoms are tetrahedrally coordinated to sulfate tetrahedra (see picture; B brown, O red, S yellow). The compound, which crystallizes in a polar space group, was investigated by X-ray diffraction, vibrational spectroscopy, and calculations.