Synthesis and Crystal Structure of Eu(ReO4)3(H2O)3 and Eu3ReO8.

Trisaquatris(tetraoxorhenate(VII)) europium(III), Eu(ReO4)3(H2O)3 was prepared by the reaction of Eu2O3 with concentrated HReO4 at room temperature. The colorless compound crystallizes in the orthorhombic space group Pna21 (No. 33) with four formula units per unit cell (a=1471.3 pm, b=843.8 pm, c=1147.1 pm). The main feature of the crystal structure is the formation of a noncentric three-dimensional network. This arrangement shows distorted tricapped trigonal prisms of Eu(H2O)3(ReO4)6/2. The compound loses the coordination water in two steps by heating until 400 K, and it decomposes to Eu3ReO8 as well as to various rhenium oxides above 1050 K. The yield of Eu3ReO8 was an orange powder, with a structure that is isotypic to that of Sm3ReO8.