Erdalkaliquadratate, II SrC₄O₄ · 3H₂O Typ I [1] / Alkaline-Earth Squarates, II SrC₄O₄ · 3H₂O Type I [1]

Abstract

Abstract In SrC 4 O 4 -3H 2 O (type I), Sr 2+ has CN 8. It is surrounded by 3 water molecules and 5 oxygen atoms of 4 different squarate dianions. The C-O and C-C bond lengths are typical of extensive delocalization of the π-electron system. The connection of Sr 2+ and C 4 O 4 2- leads to infinite layers, obviously interlinked by hydrogen bonding. The oxygens of the squarate behave differently: two are Sr-chelating, but simultaneously bound to two additional Sr 2+ , one is connected with one Sr 2+ only, and the fourth is not bound to any Sr 2+ . The single crystal character remained in principle unchanged during dehydration to SrC 4 O 4 · 1 H 2 O and subsequent rehydration to the trihydrate. Grinding of a crystal treated in this way led to a new modification of SrC 4 O 4 ·3 H 2 O.