Yttrium tetramethylheptanedionates: syntheses, crystal and molecular structures and thermal behaviours of Y(thd)3.H2O and Y(thd)3 (thd=tBuC(O)CHC(O)tBu)

F(thd)3(H2O) (I) has been prepared from yttrium nitrate via the aqueous method; its drying yielded Y(thd)3 (III). The sublimation of compound II, resulting from the reaction of yttrium isopropoxide with thdH, also yielded Y(thd)3. Compounds II and III have been characterized by elemental analysis. IR, 1H 13C{1H} and 89Y NMR spectroscopies and mass spectrometry. The thermal behaviour of each compound has been studied by TG and TD analyses. Compounds I and III crystallize in the triclinic (P anti 1) and orthorhombic (Pmn21) systems, respectively. The crystal structure determinations reveal centrosymmetric dimeric associations arising from hydrogen bonding between the water molecules and ketonic oxygen atoms for I whereas monomeric Y(thd)3 units with all thd rings in a chelating position are observed for III. The relationship between the crystal structures of I and III has been studied. (orig.)