Erdalkaliquadratate, I BaC₄O₄ · 3H₂O / Alkaline-earth Squarates, I BaC₄O₄ · 3H₂O

Abstract

Abstract BaC 4 O 4 -3H 2 O was prepared by crystallization in aqueous silica gel. The crystal structure is a complicated three-dimensional framework. Ba 2+ has CN 8+1. It is surrounded by 5 water molecules and 4 O squarate atoms (Ba-O distances from 271.1 to 324.2 pm). The squarate dianion is almost planar and shows C -C and C-O bond lengths indicating the existence of resonance stabilization, although one Osquarate atom is not connected to Ba 2+ at all. Short water-O squarate distances hint to strong hydrogen bonding which obviously plays an important part in this structure.