Lutetium(III) selenate is an inorganic compound of lutetium and the selenate ion, with the chemical formula Lu2(SeO4)3. The best-characterized hydrated form is the octahydrate, Lu2(SeO4)3·8H2O.
Preparation Lutetium(III) selenate can be prepared by reaction of lutetium(III) oxide with selenic acid followed by crystallization from solution:Perkovskaya, Yu. B.; Sukhanova, I. M. "Rare earth metal selenates". Metody Polucheniya Khimicheskikh Reaktivov i Preparatov. 1967. 16: 120–123.
Lu2O3 + 3 H2SeO4 → Lu2(SeO4)3 + 3 H2O
Crystallization from aqueous solution gives the octahydrate.Rosso, Bernard; Perret, René. "X-ray crystallographic study of selenate octahydrate of the rare earths from samarium to lutetium". Comptes Rendus de l'Académie des Sciences, Série C. 1970. 270 (11): 997–999.
Structure and properties Lutetium(III) selenate octahydrate is monoclinic. It belongs to the isostructural series Ln2(SeO4)3·8H2O formed by the smaller rare-earth ions from terbium through lutetium.
The structures of these octahydrates contain eight-coordinate Ln3+ ions bonded to oxygen atoms from selenate groups and coordinated water molecules. The compounds are closely related structurally across the heavy-lanthanide series.
Infrared spectra of the octahydrates show the characteristic internal vibrations of SeO42− tetrahedra together with O–H vibrations from the water molecules.
Thermal decomposition On heating, lutetium(III) selenate octahydrate first loses its water of crystallization to form anhydrous Lu2(SeO4)3.
Further heating causes reduction of selenium from Se(VI) to Se(IV), producing lutetium(III) selenite as an intermediate:
Lu2(SeO4)3 → Lu2(SeO3)3 + O2
Continued heating gives oxide–selenite intermediates before ultimately producing lutetium(III) oxide, Lu2O3.
The general decomposition sequence reported for the heavy rare-earth selenate octahydrates is:
Ln2(SeO4)3·8H2O → Ln2(SeO4)3 → Ln2(SeO3)3 → oxide selenites → Ln2O3
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