Titanium phosphonate oxo-alkoxide "clusters": solution stability and facile hydrolytic transformation into nano titania.

Titanium (oxo-) alkoxide phosphonate complexes were synthesized using different titanium precursors and -butylphosphonic acid (BPA) as molecular models for interaction between phosphonates and titania surfaces and to investigate the solution stability of these species. Reflux of titanium(iv) ethoxide or titanium(iv)(diisopropoxide)bis(2,4-pentadionate) with -butylphosphonic acid in toluene-ethanol mixture or acetone yielded seven titanium alkoxide phosphonate complexes; [Ti(μ-O)(μ-O)(μ-HOEt)(μ-OEt)(μ-OEt)(μ-BPA)(μ-HBPA)(μ-BPA)(μ-HBPA)]·3EtOH, 1, [TiO(μ-OEt)(μ-OEt)(μ-BPA)], 2, [Ti(μ-O)(μ-OEt)(μ-HOEt)(μ-PBA)(μ-HPBA)]·4EtOH, 3, [Ti(μ-O)(μ-OEt)(μ-HOEt)(μ-PBA)(μ-HPBA)]·2EtOH, 4, [Ti(μ-O)(μ-O)(μ-OEt)(μ-OEt)(μ-BPA)(μ-HBPA)], 5, [Ti(μ-OPr)(acac)(μ-BPA)], 6 and [Ti(μ-O)(μ-O)(μ-OEt)(μ-OEt)(μ-HOEt)(μ-BPA)], 7. The binding mode of BPA to the titanium oxo-core were either double or triple bridging or a combination of the two.