Synthesis and crystal structure of europium(II) tartrate tetrahydrate, [Eu(C4H4O6) (H2O)2](H2O)2

Single crystals of [Eu(C4H4O6)(H2O)(2)] (H2O)(2) were obtained from the combination of solutions of EuCl2, previously obtained by electrolysis of an aqueous solution of EuCl3, and tartraric acid, neutralized by LiOH. The crystal structure (orthorhombic, P2(1)2(1)2(1), Z = 4, a = 948.9(1), b = 954.6(1), c = 1098.4(1) pm; R(F) = 0.0242 and R-w(F-2) = 0.0585 for I > 2 sigma (I); R(F) = 0.0256 and R-w(F-2) = 0.0592 for all data) is isotypic with [Ca(C4H4O6)(H2O)(2)](H2O)(2) and [Sr(C4H4O6)(H2O)(2)](H2O)(2) exhibiting a three-dimensional structure. The divalent cations (Eu2+, Ca2+, Sr2+) are eight-coordinate by oxygen atoms that originate from carboxylate and hydroxyl groups of the tartraric dianion and two of the four water molecules.