Henning Höppe, together with a team from the University of Augsburg and Albert Ludwigs University Freiburg, Germany, created potassium borosulfate, K₅[B(SO₄)₄], by heating potassium sulfate with boric and sulfuric acids. It is the first example of a borosulfate (pictured; B brown, O red, S yellow).

K₅[B(SO₄)₄] crystallizes in a new structure type in the chiral space group P41. The crystal structure of K₅[B(SO₄)₄] comprises novel, large non-condensed anions [B(SO₄)₄]^5– in which a central borate tetrahedron shares all four corners with neighboring sulfate tetrahedra. These central boron atoms adopt an only slightly distorted body-centered packing with the apices of the borate tetrahedra pointing more or less directly along the c axis, resulting in a polar crystal structure. The potassium atoms are situated in the voids of the resulting structure (pictured).

The compound was investigated by X-ray diffraction, vibrational spectroscopy, and calculations.

• The First Borosulfate K₅[B(SO₄)₄],
  Henning A. Höppe, Karolina Kazmierczak, Michael Daub, Katharina Förg, Franziska Fuchs, Harald Hillebrecht,
  Angew. Chem., Int. Ed. 2012.
  DOI: 10.1002/anie.201109237