Syntheses and Crystal Structures of Er 2(SeO 3) 3 and Dy 3(SeO 3) 4F

The decomposition of Er 2(SeO 4) 3 in the presence of LiF in a sealed gold ampoule at 870°C yielded single crystals of Er 2(SeO 3) 3. The triclinic crystal structure ( P 1 , Z=2, a=698.2(1), b=800.6(1), c=895.0(1) pm, α=71.38(1), β=70.13(1), γ=65.87(1)°, R all=0.0364) contains two crystallographically different Er 3+ 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 Er 3+ ions with each other. The analogous reaction with Dy 2(SeO 4) 3 did not lead to the anhydrous selenite but to single crystals of the selenite fluoride Dy 3(SeO 3) 4F. In the hexagonal crystal structure ( P6 3 mc Z=2, a=1035.96(13), c=686.47(7) pm, R all=0.0305), one SeO 3 2− group and an F − ion act as μ 3 ligands connecting three Dy 3+ ions to triangles. The Dy 3+ 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 SeO 3 2− ions. The IR spectra show the typical frequencies for selenite groups.