Phosphazene polymers are classically synthesized by the high-temperature, ring-opening polymerization (ROP) of [PCl2N](3) to give [PCl2N](n), followed by functionalization of [PCl2N](n) with different side groups. We investigated the interactions of [PCl2N](3) with Lewis acids because Lewis acids have been used to induce the high-temperature ROP of [PCl2N](3). The reactions of [PCl2N](3) with MX3 (M = group 13, X = halides), under strict anaerobic conditions gave adducts [PCl2N](3)center dot MX3. Adducts were characterized by X-ray crystallography and multinuclear and variable-temperature NMR studies, and mechanistic understanding of their fluxional behavior in solution was achieved. The properties of the [PCl2N](3)center dot MX3 adducts at or near room temperature strongly suggests that such adducts are not involved directly as intermediates in the high-temperature ROP of [PCl2N](3).