The experimental results established the presence of unexpected [AlO 4 ] -centers in the aluminosilicate products from the reactions of the L-AlX 3 precursors with the CUBE building block. Furthermore, there appears to be a correlation between their formation and the observation of excess SnMe 4 . The process by which the excess SnMe 4 is formed is certainly less favored than the primary condensation reactions of Al-Cl, Al-Me, and Al-Et since full condensation was reached for nearly all products (1-11 and 13-15), yet a full transformation of all the [L-AlO 3 ] moieties to [AlO 4 ] -was never observed. Also, the process was observed to be strongly suppressed with more extensive cross-linking at higher AlX/CUBE ratios, while it showed no sensitivity to the type of the primary condensation reaction (and the type of the condensation byproduct). From this, it stands to reason that the formation of [AlO 4 ] -sites takes place in the late stages of the synthetic procedure -during the warm-up and heating -after the precursors have lost their initial identity to invariably become [L-AlO3] centers and after an extensive, hindering oligomer network may or may not have formed. Extensive crosslinking is expected only at the late stages of a step-growth condensation process. The strong sensitivity to the cross-linking extent, the observed evidence of additional connectivity (even to the point of sustaining microporosity in product of reaction 6), and the lack of evidence for the participation of the byproducts from the primary condensation reaction (SnMe3Cl, SnMe4, or SnMe3Et), constitute facts that all point to the unreacted Me 3 Sn-O-CUBE groups as the sole source of the additional tin removed in the form of excess SnMe 4 . Since a new negatively charged species is formed, the charge must be compensated by the formation of a counter-cation, which would represent the natural site for the liberated primary ligand (L = THF, py, Et 3 N, TEPO) to coordinate, as no free ligand was observed to leave the product.