Synthesis, crystal structures and spectroscopic characterization of [Ti8O8(OOCR)(16)] (where R = Bu-t, CH2But, C(CH3)(2)Et)

摘要

Multinuclear titanium(IV) oxo carboxylates of the general formula [Ti8O8(OOCR)(16)] (where R = Bu-t(1), CH2But (2), C(CH3)(2)Et (3)) have been synthesized in a reaction of titanium isopropoxide with the appropriate organic acids in a molar ratio of 1:2. The composition and structure of these compounds were identified by elemental analysis, IR, NMR and X-ray single-crystal diffraction. The crystal structure of 1 was solved in the orthorhombic space group Pbca. Titanium atoms form oligomeric [Ti-8(mu(2)-O)(8)] rings, where each Ti cation is surrounded by six oxygen atoms (two mu(2)-oxo and four mu-carboxylato bridges). Within the ring the Ti-Ti distances between neighboring titanium ions range from 3.333(1) to 3.366(1) angstrom and the mean value of the Ti-Ti-Ti angle is 134.2(1.3)degrees. Results of IR, NMR and MS studies proved that in the structures of 2 and 3, multinuclear [Ti-8(mu(2)-O)(8)] clusters stabilized by carboxylate bridges are also formed. TGA/DTG, MS and variable temperature IR + (VT-IR) studies have been carried out in order to determine the thermal stability and thermal decomposition mechanism of the Ti(IV) carboxylates mentioned above. (c) 2005 Elsevier Ltd. All rights reserved.