Synthesis and characterization of some bis(cyclopentadienyl)titanium(IV) complexes with internally functionalized oximes(LH):sol-gel transformations of Cp2TiCl2, Cp2TiClL and Cp2TiL~2 to nano-sized anatase titania

摘要

Some bis(cyclopentadienyl)titanium(IV) complexes of the type [Cp2TiCl_(2-n){L}_n] {where, n = 1 or 2; L = ONC(R)Ar; R = H or CH3 and Ar = C5 H4N-2, C4H3O-2 or C4H3 S-2 } have been synthesized by the metathetical reactions of Cp2TiCl2 with the sodium salt of internally functionalized oximes in 1:1 and 1:2 stoichiometry in anhydrous THF. All these red to brown colored solid derivatives have been characterized by elemental analyses, FT-IR and IMMR (~1H and ~(13)C{~1H}) spectral studies. The FAB mass spectra of some representative derivatives indicate their monomeric nature. Oximato ligands in all the complexes appear to bind the titanium via N and O in a dihapto (η~2-N, O) manner in the solid state. Thermogravimetric curves of [Cp2TiCl{ONC(CH3)C5H4N-2}] and [Cp2Ti{ONC(CH3)C5H4N-2}2] suggest the formation of hybrid materials CpTiO(Cl) and Cp2TiO, respectively, as the final products at 900°C under nitrogen atmosphere. Sol-gel transformations of Cp2TiCl2, [Cp2TiCl{ONC(CH3)C5H4N-2}] and [Cp2Ti{ONC(CH3)C5H4N-2)2] yielded titania a-c, respectively, at low sintering temperature (600 °C). The powder XRD patterns, IR as well as Raman spectra of all these oxides indicate the formation of nano-sized anatase phase. The SEM images of titania a-c indicate agglomers like surface morphologies. The absorption spectra of a-c exhibit an energy band gap in the range of 3.47-3.71 eV.