Based on the aforementioned evidence, a two-step process is proposed (Figure ). In Since the Al TQ/MAS NMR analysis supports the presence of at least one bidentate CUBE at each [AlO 4 ] -center, only pathways leading to such arrangements are considered. In the simplest case, the initial L-Al(OCUBE)3 center is attacked by a neighboring Me3SnO-group of one of the directly connected CUBEs, making it bidentate (Figure ). Based on a series of structure optimizations using molecular mechanics, only a single mode of bidentate binding was found feasible -along the edge of the CUBE. While this pathway may be partially responsible