Eight macroporous styrene–divinylbenzene–vinylbenzyl chloride resins have been synthesised by suspension polymerisation. The first four employed toluene as the porogen and the second four n-butyl acetate, at a level of 1 ∶ 1 v/v relative to the comonomers. In all cases a high level of divinylbenzene leads to resins with high surface area, ∼500 m2 g−1, as determined from a BET treatment of N2 sorption data. The functional group content of each group of four resins was varied from 5–25%. All resins were aminated to generate benzyltrimethylethylenediamine ligands on the polymer matrix, and then each was loaded with Pt(II) using KPtCl4. The analytical data confirmed the formation of ligand PtCl2 molecular complexes. Each of the resin immobilised Pt complexes has been assessed for catalytic activity in the room temperature, solventless, hydrosilylation of oct-1-ene
using methyldichlorosilane, and a comparison made with soluble Speier's catalyst under identical conditions. Though less active than the soluble catalyst the activity of all the polymer catalysts is good, and of practical value, the activity being higher than we have previously reported in the case of supports with lower surface area. Furthermore while Speier's catalyst induces significant levels of oct-1-ene isomerisation, isomerisation in the case of the polymer catalysts is much lower, and indeed can be all but eliminated by appropriate washing. Extensive catalyst leaching and recycling studies have been carried out, with the best catalysts showing retention of useful activity after 10 cycles. Careful control experiments have provided strong circumstantial evidence that the isomerisation that does arise with the polymer catalysts can be attributed to a component of leached soluble Pt species. Overall the most active and stable polymer catalyst has the highest surface area (∼550
m2 g−1) of those studied, along with the lowest ligand and Pt contents (each ∼0.25 mmol g−1). The surface area dependence confirms our earlier view that maximum accessibility to potential metal complex catalytic sites is vital in these systems, and the metal complex loading dependence suggests that generating discrete isolated ligand PtCl2 species provides optimal use of the loaded Pt.
通过悬浮聚合法合成了八种大孔
苯乙烯-
二乙烯基苯-
乙烯基苄基
氯树脂。前四种使用
甲苯作为增孔剂,而后四种使用n-
丁基乙酸酯,相对于共聚单体以1:1的体积比使用。在所有情况下,高含量的
二乙烯基苯导致
树脂具有高比表面积,约为500平方米/克,这是通过BET处理N2吸附数据确定的。每组四种
树脂的功能基含量从5%到25%不等。所有
树脂都经过了胺化处理,以在聚合物基质上生成苄基甲基
乙烯二胺
配体,然后使用K2PtCl6加载Pt(II)。分析数据显示形成了
配体PtCl2分子复合物。每种
树脂固定的Pt复合物都被评估了其在室温下无溶剂的辛-1-烯与甲基二
氯硅烷的氢
硅化反应中的催化活性,并在相同条件下与可溶的Speier催化剂进行了比较。尽管活性不如可溶催化剂,但所有聚合物催化剂的活性都很好,具有实用价值,其活性高于我们之前在比表面积较低的载体上报道的活性。此外,虽然Speier催化剂导致辛-1-烯异构化
水平显著,但聚合物催化剂的情况中异构化
水平要低得多,实际上可以通过适当的洗涤几乎消除。进行了大量的催化剂浸出和回收研究,最好的催化剂在经过10个循环后仍保持有用的活性。仔细的控制实验提供了强有力的旁证,表明聚合物催化剂引发的异构化可以归因于浸出的可溶Pt物种的组分。总体上,最活跃和稳定的聚合物催化剂具有最高的比表面积(约550平方米/克),以及最低的
配体和Pt含量(每个约0.25毫摩尔/克)。比表面积的依赖性证实了我们早先的观点,即可获得潜在
金属复合物催化位点的最大可达性在这些系统中至关重要,而
金属复合物负载的依赖性表明生成孤立的
配体PtCl2物种提供了加载Pt的最佳利用。