Crystal Structure of the Gadolinium Trihydrogenohydroxy-1 Ethane Bis(Phosphonate)-1,1″ Trihydrate

Abstract

The title complex salt Gd[C(CH₃)(OH)(PO₃H)(PO₃)],3H₂O is obtained by progressive dissolving of gadolinium carbonate in an aqueous solution of hydroxyethylidenebisphosphonic acid (HEBP). This compound crystallizes with the orthorhombic space group Pbca (n°61) and a = 9.690(1) Å, b = 9.744(2) Å, c = 20.585(4) Å, V = 1943.7(5) ų, and Z = 8. The coordinence of Gadolinium is 8 and the corresponding polyhedra are associated two by two by sharing an edge to form centrosymmetric “bipolyhedra.” The crystal cohesion is assumed by one interligand hydrogen bond and mainly by the hydrogen bond network given by the three water molecules. This compound, where the ligand is tri-ionized, is totally different from the other known lanthanide salts (Ln = Ho, Er, Y) where mono- and di-ionized HEBP ligands coexist with the ratio 1/1.

Key Words:

• Crystal structure
• gadolinium
• hydroxyethylidenebisphosphonate