Abstract
Niobium isopropoxide, Nb(OiPr)5, is an attractive precursor of simple and complex niobium oxides in sol-gel technology. This compound cannot, unfortunately, be obtained by alcohol interchange starting from linear chain homologues such as Nb(OMe)5 or Nb(OEt)5. The equilibrium in the latter reaction favours formation of mixed-ligand complexes, [Nb2(OR)2(OiPr)8], R = Me, Et. In particular, [Nb2(OMe)2(OPri)8] (1) has been isolated in high yield from repeated treatment of Nb2(OMe)10 with excess of isopropanol. The X-ray single crystal study reveals a dinuclear structure containing a pair of edge-sharing octahedra with methoxide ligands in the bridging position. Infrared (IR) and mass spectroscopy (MS) studies confirmed the incomplete ligand substitution. The 1H-NMR spectra suggest equilibrium between different molecular forms in solution. Solvothermal interaction of 1 with La chips in toluene/isopropanol media results in formation of a mixture of LaNb2(OiPr)13 and La2Nb4(μ4−O)4(OH)2(μ−OiPr)8(OiPr)8 (2).
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