Preparation, Crystal Structures and Thermal Decomposition of Ba2(EDTA) and Ba2(EDTA)·2.5H2O

Abstract The barium ethylenediaminetetraacetato (EDTA) complexes, Ba 2 (EDTA) and Ba 2 (EDTA) · 2.5H 2 O, were hydrothermally synthesized and characterized by single‐crystal X‐ray structure determination. Ba 2 (EDTA) (monoclinic, P 2 1 / c , (No.14), a = 9.7651(10) Å, b = 8.0870(6) Å, c = 10.3313(11) Å, β = 118.024(4)°, V = 720.20(12) Å 3 , Z = 2) exhibits a layered arrangement of coordination polyhedra around barium whereas in the crystal structure of Ba 2 (EDTA) · 2.5H 2 O (tetragonal, P 4 nc , (No.104), a = 19.7126(7) Å, c = 8.9813(4) Å, V = 3490.0(2) Å 3 , Z = 8) a completely different three dimensional framework containing wide channels is formed. Thermoanalytical investigations reveal a reversible dehydration behavior for Ba 2 (EDTA) · 2.5H 2 O. The anhydrous form was characterized by PXRD ( tP , a = b = 19.226(10) Å, c = 8.986(3) Å, V = 3335.4(3) Å 3 ) and is assumed to be closely related to the crystal structure of the hydrated starting material. The final decomposition product of both compounds after heating in air up to 1000 °C was found to consist of pure BaCO 3 .