(n = 1-3) as well as the very similar Me3SiCl directly as a capping agent to remove the residual -SnMe3 groups left in the prepared metallosilicate matrices. The results show that SiCl4 is one of the most exoergic precursors with estimated ΔG 298.15 ranging from -102 to -75 kJ mol -1 while the condensation of Me3SiCl is moderated by the positive inductive effect of the methyl substituents to -60.2 / -54.9 kJ mol -1 by B3LYP-D3 and PBE0-D3, respectively. Surprisingly, the condensation of PhMe2SiCl is predicted to be even slightly more energetic than that of Me3SiCl, despite our expectations that a positive mesomeric effect of the phenyl substituent would decrease the reactivity even further. The reactivity of compounds such as HSiCl3 and Me2SiCl2 is expected to range somewhere between the extremes of SiCl4 and Me3SiCl. In conclusion, there is no doubt about the irreversibility of the condensation reaction for any Si-Cl precursors.