The results show that while the additional coordination of THF is favored at 0 K (for py-AlCl3 and py-Al(OSiH3)3 by 50 kJ mol -1 ), it is disfavored at 298.15 K for all states. This agrees with our recent experimental observations, where no evidence for 5-or 6-coordinated Al species was observed in Al TQ/MAS NMR spectra of dried products prepared in THF. While the results are completely realistic for the initial precursors, model A falls short of representing the steric demands of CUBE, therefore, in reality, the coordination of THF to py-AlMe3-x(OCUBE)x (x = 1-3, equivalent to states Me2, Me1, and O in Figures and) and py-AlCl3-x(OCUBE)x (x = 1-3, equivalent to states Cl2, Cl1, and O) can be expected to be progressively more disfavored with the increasing number of CUBEs in the coordination sphere of Al, even at 0 K. The interaction of the incoming CUBE with the coordinated THF will likely result in an increased reaction barrier. The comparison of the energy difference between the 4-(4C) and 5-coordinated (5C) states (equivalent to the Gibbs energy change of coordination of THF to the 4-coordinated Al species) shows that the dative coordination is most favored by py-AlCl3 and least by py-AlMe3. The final aluminosilicate site is comparable to py-AlCl3 at low temperatures and it assumes a behavior intermediate between the two precursors at higher temperatures. This has the minor effect of generally decreasing ΔG of the condensation steps starting from py-AlCl3(THF) and increasing it for py-AlMe3(THF).