A series of multicarboxylic acid appended imidazolium ionic liquids (McaILs) with chloride [Cl]– or bromide [Br]– as anions have been synthesized and characterized. Deprotonation of these ionic acids gives the corresponding zwitterions. Re-protonation of the zwitterions with strong Brønsted acids gives a series of new ionic acid-adducts, many of which remained as room-temperature ionic liquids. A new catalytic system, McaIL/PdCl2 for the selective catalytic oxidation of styrene to acetophenone with hydrogen peroxide as an oxidant has been attempted. In the presence of McaILs, it is found that the quantity of palladium chloride PdCl2 used can be greatly reduced while the activity (TOF) and selectivity towards acetophenone are enhanced sharply. It is also shown that the catalytic properties of this system could be finely tuned through the molecular design of the McaILs. The best TOF value obtained so far is 146 h–1 with 100% conversion of styrene at 93% selectivity to acetophenone. In addition, the catalytic activity has been maintained for at least ten catalytic cycles.
我们合成了一系列以
氯[Cl]-或
溴[Br]-为阴离子的多
羧酸附加
咪唑离子液体(McaILs),并对其进行了表征。对这些离子酸进行去质子化可得到相应的齐聚物。这些齐聚物与强勃氏酸发生再质子化反应,产生了一系列新的离子酸加成物,其中许多仍然是室温
离子液体。我们尝试了一种新的催化体系--McaIL/PdCl2,用于以
过氧化氢为氧化剂将
苯乙烯选择性催化氧化为
苯乙酮。研究发现,在 McaIL 的存在下,
氯化钯 PdCl2 的用量可以大大减少,而活性(TOF)和对
苯乙酮的选择性却大幅提高。研究还表明,该系统的催化特性可以通过对 McaILs 的分子设计进行微调。目前获得的最佳 TOF 值为 146 h-1,
苯乙烯的转化率为 100%,对
苯乙酮的选择性为 93%。此外,这种催化活性还能保持至少十次催化循环。