Katayama H, Kamigaito M, Sawamoto M
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan.
Macromolecules. 1998 Jul 28;31(15):4703-9. doi: 10.1021/ma980320r.
119Sn NMR spectroscopy was employed for analysis of the interaction and reaction of SnCl4 with the HCl-IBVE adduct [1; CH3CHCl(OiBu)] in the presence of nBu4NCl in CH2Cl2 solution at -78 degreesC, which are model reactions for the living cationic polymerization of isobutyl vinyl ether (IBVE). The addition of 1 to an SnCl4 solution led to upfield shifts of the tin nucleus as the 1/SnCl4 mole ratio (<1) increases, which indicates the formation of SnCl5-, via the interaction between SnCl4 and the chlorine atom in 1. On further addition of 1, the pentacoordinated anion is converted into the hexacoordinated SnCl62-. These tin species are in fast equilibrium among each other, and the 119Sn NMR analyses support the formation of a carbocation [2; CH3CH+(OiBu)] from 1 and the dynamic equilibrium between 1 and 2. More effective chloride-anion donors such as nBu4NCl and Ph3CCl can quantitatively convert SnCl4 into SnCl5-, and then into SnCl62-. Thus under the conditions where living cationic IBVE polymerization proceeds (1 < nBu4NCl/SnCl4 < 2), SnCl4 is fully converted into a weaker Lewis acid, SnCl5-, with the aid of added nBu4NCl. The suppression of the carbocationic species in the living system has thus been found due to the interaction between the added salt and SnCl4.
采用119Sn核磁共振光谱法，在-78℃的二氯甲烷溶液中，于四丁基氯化铵存在的条件下，分析四氯化锡与HCl-异丁基乙烯基醚加合物[1；CH3CHCl(OiBu)]的相互作用和反应，这些反应是异丁基乙烯基醚（IBVE）活性阳离子聚合的模型反应。当1与四氯化锡溶液混合时，随着1/四氯化锡摩尔比（<1）的增加，锡核发生高场位移，这表明通过四氯化锡与1中氯原子的相互作用形成了SnCl5-。进一步加入1后，五配位阴离子转化为六配位的SnCl62-。这些锡物种彼此之间处于快速平衡状态，119Sn核磁共振分析支持了由1形成碳正离子[2；CH3CH+(OiBu)]以及1和2之间的动态平衡。更有效的氯阴离子供体，如四丁基氯化铵和三苯基氯甲烷，可以将四氯化锡定量转化为SnCl5-，然后再转化为SnCl62-。因此，在活性阳离子IBVE聚合反应进行的条件下（1 < 四丁基氯化铵/四氯化锡 < 2），借助添加的四丁基氯化铵，四氯化锡完全转化为较弱的路易斯酸SnCl5-。因此，由于添加的盐与四氯化锡之间的相互作用，已发现活性体系中的碳正离子物种受到抑制。
