Synthesis and characterization of tridentate phosphine ligands incorporating long methylene chains and ethoxysilane groups for immobilizing molecular rhodium catalysts
Synthesis and characterization of tridentate phosphine ligands incorporating long methylene chains and ethoxysilane groups for immobilizing molecular rhodium catalysts
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DOI：
10.1016/j.mcat.2019.110629
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发表时间：
2019-12-01
影响因子：
4.6
通讯作者：
Blumel, J.
中科院分区：
文献类型：
--
作者：
Guenther, J.;Reibenspies, J.;Blumel, J.
新的三齿膦配体EtOSi（（CH 2）（n）PPh 2）（3）和O[Si（（CH 2）（n）PPh 2）（3）]（2）（n = 4，7，11），以及它们的前体乙氧基硅烷EtOSi（（CH 2）（m）CH = CH 2）（3）和二硅氧烷O[Si（（CH 2）（m）CH = CH 2）（3）]（2）（m = 2，5，9）和EtOSi（CH_2）（11）PPh_2RhClCOD）（3）（COD =环辛烯）的合成和表征。已通过共价硅氧烷键将含乙氧基硅烷和二正辛烷的膦配体固定在二氧化硅上。已通过P-31和Si-29 CP/MAS和HRMAS NMR光谱表征了固定化的接头。连接体和二氧化硅表面之间的共价硅氧烷键阻止膦的平移移动性。通过ClRh（PPh 3）（3）和ClRhpyCOD（py =吡啶）与表面结合的配体的配体交换，获得了固载化的Wilkinson型Rh加氢催化剂。报道了ClRhpyCOD的单晶X射线结构。研究了它们对1-十二烯加氢反应的活性和寿命。新的催化剂具有高活性，可循环使用多达15次，而活性不会有重大损失。在催化反应的最初几个小时内，最初的分子络合物在表面上形成具有窄尺寸分布的Rh纳米颗粒。纳米颗粒不会浸出到上清液中，并且对空气不敏感。
The new tridentate phosphine ligands EtOSi((CH2)(n)PPh2)(3) and O[Si((CH2)(n)PPh2)(3)](2) (n = 4, 7, 11), as well as their precursor ethoxysilanes EtOSi((CH2)(m)CH = CH2)(3) and disiloxanes O[Si((CH2)(m)CH = CH2)(3)](2) (m = 2, 5, 9) and EtOSi(CH2)(11)PPh2RhClCOD)(3) (COD = cyclooctadiene) have been synthesized and fully characterized. The ethoxysilane- and disiloxane-containing phosphine ligands have been immobilized on silica via covalent siloxane bonds. The immobilized linkers have been characterized by P-31 and Si-29 CP/MAS and HRMAS NMR spectroscopy. The covalent siloxane bonds between the linkers and the silica surface prevent translational mobility of the phosphines. Immobilized Wilkinson-type Rh hydrogenation catalysts have been obtained by ligand exchange of ClRh(PPh3)(3) and ClRhpyCOD (py = pyridine) with the surface-bound ligands. The single crystal X-ray structure of ClRhpyCOD has been reported. The activities and lifetimes have been studied for the hydrogenation of 1-dodecene. The new catalysts are highly active and they can be recycled up to 15 times without major loss of activity. Within the first hours of the catalytic reaction the initially molecular complexes form Rh nanoparticles with a narrow size 'distribution on the surface. The nanoparticles do not leach into the supernatant solution and are not air-sensitive.