Group 13 Lewis Acid Adducts of [PCl2N]3

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·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·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.

磷腈聚合物（Phosphazene polymers）的经典合成路径为：先通过高温下[PCl₂N]₃的开环聚合（ring-opening polymerization, ROP）得到[PCl₂N]ₙ，随后利用不同侧基对[PCl₂N]ₙ进行官能化改性。我们针对[PCl₂N]₃与路易斯酸（Lewis acids）的相互作用展开了研究，这是由于路易斯酸常被用于引发[PCl₂N]₃的高温开环聚合。在严格无氧的条件下，[PCl₂N]₃与MX₃（M为第13族元素，X为卤原子）发生反应，得到加合物[PCl₂N]₃·MX₃。通过X射线晶体学（X-ray crystallography）以及多核、变温核磁共振（NMR）研究对该加合物进行了表征，并对其在溶液中的动态流变行为的机理进行了阐释。该[PCl₂N]₃·MX₃加合物在室温及近室温条件下的性质强烈表明，此类加合物并未直接作为中间体参与[PCl₂N]₃的高温开环聚合过程。