基于“配体(催化剂)和离子液体一体化”的高效、超长寿命催化体系的创建及其在均相催化反应中的应用

Over the last two decades, the separation and recycling of transition metal catalysts have been a vital problem in homogeneous catalysis and continue to attract intense attention. It remains a challenge for researchers how to combine the advantages of both homogeneous and heterogeneous catalysis systems by the heterogenization of homogeneous catalysts or by carrying out homogeneous reactions under heterogeneous conditions to establish the highly effective and long-life catalytic system. Recently, we have reported the novel room temperature liquid-solid phase transition guanidinium ionic liquids with a polyether tag and their use in Rh-catalysed biphasic hydroformylation of higher olefins. These new polyether guanidinium ionic liquids (PGILs) can very effectively immobilize the Rh-TPPTS catalyst and notably stabilize the catalytically active Rh species. In the light of main disadvantages in ionic liquid two-phase catalytic system, such as requiring a large amount of ionic liquid, poor mass transfer and fast catalyst deactivation, the phosphine-tagged polyether guanidinium ionic liquids (PPGILs) with room temperature liquid-solid phase transition characteristic are designed and synthesized via the ion exchange reaction of sulfonated phosphine ligands and PGILs based on the new concept of integrated ligand (or catalyst) and ionic liquid. A novel "homogeneous catalysis and liquid-solid separation" catalytic system is established based on PPGILs for hydroformylation and hydrogenation, in which PPGIL as a task-specific ionic liquid can act not only as a carrier but as a ligand to minimize the amount of utilized ionic liquid in a catalytic process. The advantages of homogeneous and heterogeneous catalysis herein will be combined perfectly with high activity, much simplified catalyst separation and super long life time of catalyst. The effects of structures and properties of PPGILs on catalytic activity and selectivity will be investigated. The relation between structure of PPGILs and reusability of transition metal catalysts will be examined. It is the purpose of this investigation to overcome disadvantages of ionic liquid biphasic catalysis and offer a catalytic system that can realize the combination of high efficiency and super long life of catalyst by integrating the catalytic reaction and catalyst separation. This investigation will enrich the scientific connotation of homogeneous catalysis under ionic liquid conditions and provide the experimental and theoretical support for bridging homogenous and heterogeneous catalysis.

过渡金属催化剂的分离和循环使用是均相催化的一个核心问题，如何将均相催化和多相催化的优点融为一体，进而构建高效、超长寿命的催化体系一直是具有挑战性的研究课题。申请人近期的研究发现，聚醚烷基胍盐离子液体(PGIL)能够有效稳定铑催化剂。本申请针对均相催化体系中催化剂难分离和离子液体两相体系下离子液体用量大、传质慢和催化剂失活快的关键不足，首次提出“催化剂和离子液体一体化”的概念，创制出一种新型的具有室温液-固相变特性的膦功能化聚醚烷基胍盐离子液体(PPGIL)，基于PPGIL的功能性和室温相变性质，创建一类新型的“均相催化-液/固分离”催化体系，并应用于氢甲酰化和不对称氢化反应中。研究PPGIL的构性关系及催化反应的规律，揭示催化剂的稳定性与PPGIL构性之间的相关性，探明并诠释催化剂稳定的机理。课题的实施将开创一类高效且兼具超长使用寿命的催化体系，为均相催化和多相催化的交叉融合提供理论支持。

传统的两相离子液体催化的主要局限是大量使用溶剂离子液体来溶解和负载均相催化剂，这不仅违反了绿色化学原理，而且降低了催化反应效率。因此，如何更高效、更经济、更绿色地利用离子液体，构建高效、长期稳定的离子液体催化体系一直是一个挑战。本研究基于膦配体和离子液体一体化的概念，通过聚醚胍盐离子液体（PolyGILs）与膦磺酸盐配体之间的离子交换反应，合成了一类室温膦功能化聚醚胍盐离子液体（RTP-PolyGILs）。RTP-PolyGILs具有膦配体和溶剂离子液体的双重特征，既可以与过渡金属络合形成催化剂，又可以作为催化剂载体，从而实现了配体（催化剂）和溶剂离子液体的一体化。通过改变聚醚链的乙氧基数（EO值）和封端基团，可以方便地调节RTP-PolyGILs的熔点和溶解性。基于这种多功能集成的RTP-PolyGILs的独特性质，我们构建了一个高效的均相催化-两相分离（HCBS）催化体系用于铑催化的高碳烯烃的氢甲酰化反应。在该体系中，仅使用催化量的RTP-PolyGILs（相当于1-烯烃的0.025-0.4 mol %）即可使催化反应高效的进行，并实现催化剂的高效分离。HCBS体系融合了均相催化和两相催化的优点，通过改变RTP-PolyGILs上磺化膦配体阴离子的结构或类型，可以灵活调控催化剂的性能（催化活性和区域选择性）。该体系的最高TOF值高达3000–26000 h−1，正异比可达到2.2/1–37.5/1。铑催化剂表现出超长期的稳定性，总转化数（TTON）高达11000–45000，Rh催化剂的流失仅为0.02–0.4 ppm。在此基础上，我们还将HCBS体系成功地应用于高碳烯烃的加氢反应，以及β-羰基酸酯的不对称加氢反应，证明了RTP-PolyGILs对不同的催化反应具有良好的普适性。