Synthesis, structure and properties of two unexpected square pyramidal pentanuclear oxo-isopropoxide molecules: Ce5O(OPri)13 and La5O(OPri)13(HOPri)2

The synthesis, structure and properties of two pentanuclear oxo-alkoxides are described. A combination of metathesis of LnCl3 and 3KOPri and stoichiometric hydrolysis resulted in the solvated oxo-alkoxide La5O(OPri)13(HOPri)2 (1) and the non-solvated Ce5O(OPri)13 (3). 1 is rather stable at room-temperature, but desolvation into La5O(OPri)13 (2), identified by spectroscopy, could be achieved by vacuum treatment. 1 and 3 were structurally characterised by single-crystal X-ray diffraction. In both 1 and 3 the metal atoms have a square pyramidal arrangement. In 1, each crystallographically independent La5O(OPri)13(HOPri)2 molecule contains 3 six-coordinated and 2 seven-coordinated La atoms, while in 3 all Ce atoms are six-coordinated. 3 Is the first structurally characterized example of a purely Ce3+ isopropoxide. Characterisations of 1 and 3 were by IR- and Raman spectroscopy and differential scanning calorimetry, and for 1 also by 1H and 13C NMR spectroscopy. The great similarity of the IR spectra of the solid 1 and 3, respectively, to their corresponding solutions, showed that the molecular structure present in the solid state is close to retained in solution.