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A recyclable catalyst that precipitates at the end of the reaction

机译：在反应结束时沉淀的可回收催化剂

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摘要

Homogeneous catalysts―which exist in the same (usually liquid) phase as reactants and products―are usually more selective than heterogeneous catalysts and far less affected by limitations due to slow transport of reactants and products, but their separation from reaction products can be costly and inefficient. This has stimulated the development of strategies that facilitate the recycling of homogeneous catalysts. Some of these methods exploit the preference of a catalyst for one of two solvents with thermoregulated miscibility; others exploit a dramatic decrease in catalyst solubility as one reagent is consumed or temperature changed after completion of the reaction. Here we describe a tungsten catalyst for the solvent-free hydrosilylation of ketones that retains its activity until essentially all of the liquid substrate is converted to liquid products, which we can then simply decant to separate the catalyst that precipitates from the products of the reaction. We attribute the ability of the catalyst to retain its solubility and hence activity until completion of the reaction to the transient formation of liquid clathrate that contains a few molecules of the substrate per molecule of the otherwise solid catalyst. Insights into the fundamental processes controlling the formation of this liquid clathrate might help to tailor other catalysts and substrates, so as to develop efficient and solvent-free schemes for reactions of practical interest.
机译：与反应物和产物存在于同一个（通常为液相）相中的均相催化剂通常比非均相催化剂更具选择性，并且由于反应物和产物的缓慢运输而受到限制的影响要小得多，但是它们与反应产物的分离成本高且效率低下。这刺激了促进均相催化剂再循环的策略的发展。这些方法中的某些方法利用了催化剂对具有可调节温度混溶性的两种溶剂之一的偏爱。另一种方法则是在反应完成后消耗一种试剂或改变温度，从而大大降低催化剂的溶解度。在这里，我们描述了一种用于酮的无溶剂氢化硅烷化的钨催化剂，该催化剂保持其活性，直到基本上所有的液体底物都转化为液体产物为止，然后我们可以简单地倾析以从反应产物中分离出沉淀出的催化剂。我们将催化剂保持其溶解度以及因此直至反应完成的活性的能力归因于液态包合物的瞬时形成，该包合物每分子否则为固态的催化剂中含有几分子底物。对控制该液体包合物形成的基本过程的深入了解可能有助于定制其他催化剂和底物，从而为实际感兴趣的反应开发高效且无溶剂的方案。

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  • 来源
    《Nature》 |2003年第6948期|p.530-532|共3页
  • 作者

    Vladimir K. Dioumaev; R. Morris Bullock;

  • 作者单位

    Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然科学总论;
  • 关键词

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