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.

Metathesis of LnCl3 and 3KOPri and hydrolysis with 0.2H2O/Ln resulted in the solvated oxo-alkoxide La5O(OPri)13(HOPri)2 and the non-solvated Ce5O(OPri)13. The former has a sqp molecular structure in contradiction to the previously known tbp Nd5O(OPri)13(HOPri)2 and the latter is the first structurally characterized purely Ce3+ isopropoxide, sometimes believed not to be isolable.Figure optionsDownload as PowerPoint slideHighlights
► Three oxo-alkoxides; Ln5O(OPri)13 (Ln = La or Ce) and La5O(OPri)13(HOPri)2 were synthesized and described.
► The structures of Ce5O(OPri)13 and La5O(OPri)13(HOPri)2 were determined by single crystal XRD.
► Ce5O(OPri)13 has the same square planar structure as other known Ln5O(OPri)13 molecules.
► La5O(OPri)13(HOPri)2 is square pyramidal, differentiating it from Nd5O(OPri)13(HOPri)2 which is trigonally bipyramidal.