Our calculations concur with the predicted ΔG 298. The reaction of TiCl4 (12A/12B) was reported (along with ZrCl4 and SiCl4) by Barnes et al., who successfully used multistep template-free procedures to obtain micro-mesoporous titano-and zirconosilicates. Calculations showed that the condensation of TiCl4 is highly exoergic with ΔG 298.15 ranging from nearly -80 kJ mol - 1 for the first step to -57 kJ mol -1 for the last step, making it irreversible. Reactions of CUBE with Cp2TiCl2 were reported by Clark et al., who obtained a molecular substitution product of CUBE Si8O20(Cp2TiCl)8 in high yield. In harmony with this experimental observation, our calculations show that the condensation of this precursor is nearly half as energetic as TiCl4 with ΔG 298. ranging from over -40 kJ mol -1 to approximately -32 kJ mol -1 . Since the steric repulsion between the cyclopentadienyl rings and the CUBE(s) is completely neglected by model A (and the results given by model B for the first condensation step do not significantly differ), this deactivation compared to TiCl4 is attributed in large part to electronic effects -the electron-donating ability of the Cp rings. The Cp rings will impose additional steric repulsion and, especially in the case of the second condensation, a large additional penalty can be expected, explaining the apparently high activation barrier of the reaction and the tendency for stepwise substitution.