The previous part of the discussion provided an explanation for the combined appearance of the [AlO4] -moiety together with the unexpected formation of SnMe4 in the reactions of L-AlX3 compounds. This, however, cannot explain the observation of significant amounts of SnMe 4 in reactions with [Me4N] [AlCl4] (Table ), where no such transformation is possible and no other types of Al sites were observed (Figure ). A closer analysis revealed a fundamental difference -the SnMe 4 is generated instead of SnMe 3 Cl and not in addition to it, resulting in exactly 4 eq. of byproducts liberated per Al (average connectivity 3.98). Based on the experimental observation that the missing Cl does not leave the material in any form, a synchronous trimolecular mechanism is proposed as the simplest possible explanation (Figure ). In an otherwise regular primary condensation reaction, the activated Cl -nucleophile attacks a second