Syntheses and Crystal Structures of Er2(SeO3)3 and Dy3(SeO3)4F

The decomposition of Er2(SeO4)3 in the presence of LiF in a sealed gold ampoule at 870°C yielded single crystals of Er2(SeO3) 3. The triclinic crystal structure (P , Z=2, a=698.2(1), b=800.6(1), c=895.0(1) pm, ALPHA=71.38(1), BETA=70.13(1), GAMMA=65.87(1)°, Rall=0.0364) contains two crystallographically different Er3+ ions in seven- and eightfold coordination of oxygen atoms, respectively. The distances Er–O range from 220 to 256 pm. Each of the three crystallographically different selenite groups connects four Er3+ ions with each other. The analogous reaction with Dy2(SeO4)3 did not lead to the anhydrous selenite but to single crystals of the selenite fluoride Dy3(SeO3)4F. In the hexagonal crystal structure (P63mcZ=2, a=1035.96 (13), c=686.47(7) pm, Rall=0.0305), one SeO32- group and an F- ion act as MU3 ligands connecting three Dy3+ ions to triangles. The Dy3+ ions are coordinated by eight oxygen atoms and one fluoride ion with distances between 234 and 256 pm. The crystal structures are strongly influenced by the lone pairs of the SeO32- ions. The IR spectra show the typical frequencies for selenite groups.