The borosulfates are heteropoly anion compounds which have sulfate groups attached to boron atoms.
The first borosulfate to be discovered was K5[B(SO4)4] in 2012 by the research group of Henning Höppe,[1][2] although the compound class as such had been postulated already in 1962 by G. Schott and H. U.
Related compounds include boroselenates, borotellurates,[4] and also boroantimonates, borogallates, borogermanates, borophosphates, boroselenites and borosilicates.
[5] Borosulfates are formed by heating boric oxide, oleum, or sulfuric acid, with metal carbonates.
When heated to around 500 °C the borosulfates decompose by emitting SO3 vapour and form a metal sulfate and boric oxide.