Synthesis and characterisation of new titanium amino-alkoxides: precursors for the formation of TiO2 materials

摘要

Reaction of the amino-alkoxides HOCH(CH_2NMe_2)(2) (Hbdmap) and HOC(CH_2NMe_2)_3 (Htdmap) with [Ti(OR)_4] yields a series of heteroleptic titanium alkoxides [Ti(OR)_(4-n)(L)_n)] (L = bdmap, tdmap). Substitution of the monodentate alkoxide with the chelating alkoxides becomes progressively more difficult, with homogeneous products being obtained only for n = 1, 2. The structure of [Ti(ORrEt)_3(bdmap)](_2), a mu-OEt bridged dimer, has been determined. Hydrolysis of [Ti(OR)(_2)(L)(_2)], by adventitious moisture affords the dimeric oxo-alkoxides [Ti(O)(L)(2)](2), both of which have been characterised crystallographically. These two compounds have also been prepared by reaction of [Ti(NMe2)(_2)(L)(2)] with the hydrated metal salts [Zn(acac)(2)center dot 2H(2)O] and [Zn(OAc)(2)center dot 2H(2)O] using the intrinsic water molecules in these salts to react with the labile amido groups, though the former also produces Me(Me2N)C=C(H)C(O)Me from reaction of liberated HNMe2 with the coordinated acac ligand, while the latter also affords the ligand exchange product [Zn(OAc)(bdmap)]. In neither case does the free dimethylamino group of [Ti(O)(L)2]2 coordinate a second metal. The dimeric structure of [Zn(OAc)(bdmap)](2) has been established, and the structure of the tetrameric oxo-alkoxide [Ti(O)(OPri)(OCH2CH2NMe2)](4) is reported for comparison with others in this study. [Ti(OEt),(bdmap)]2 has been used as a precursor in AACVD (Aerosol-Assisted Chemical Vapour Deposition) to generate amorphous TiO2 films on glass at 440 degrees C, and TiO2@C nanoparticles of approximate diameter 350 nm with a carbon coating of width ca. 75 nm on heating in a sealed container at 700 degrees C.