Alkoxide Clusters in Solution: An EXAFS Study of the Example Y(OEtOMe)₃ and the Degradation Induced by Structural Modifiers

<jats:title>Abstract</jats:title> <jats:p>Yttrium methoxyethoxide Y(OEtOMe)<jats:sub>3</jats:sub> is an important precursor for the sol-gel preparation of Y<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>-containing materials. Its aggregation degree and the clusters, formed in solution of 2-methoxyethanol and modified by the ligands Hacac, <jats:sup> <jats:italic>i</jats:italic> </jats:sup>PrOH and THF are studied by means of EXAFS spectroscopy. The cluster geometries of the formed complexes deviate from the well-known cyclic decameric structure of the crystalline solid Y(OEtOMe)<jats:sub>3</jats:sub>. A pentanuclear square-pyramidal framework, which was found for Y(OEtOMe)<jats:sub>3</jats:sub>, dissolved in 2-methoxyethanol in a previous study, is confirmed by a detailed discussion of the structural EXAFS parameters. While the addition of the Lewis bases <jats:sup> <jats:italic>i</jats:italic> </jats:sup>PrOH and THF does not change the aggregation degree and short range order of Y(OEtOMe)<jats:sub>3</jats:sub> in solution, chelating Hacac causes a stepwise degradation of the original pentameric metal framework. Details of the degradation pathway as deduced from the EXAFS results are given, which could not be achieved by any other spectroscopic method so far. The yttrium coordination number and third cumulants, which are necessary to account for asymmetry in the individual shells, are used in order to identify structural changes of the samples in comparison with the initially formed Y<jats:sub>5</jats:sub>-complex.</jats:p>