含吡啶配体的钌催化剂合成及在离子液体中开环易位聚合反应

Synthesis of Pyridyl-based Ionic Liguid Supported Ruthenium Complex and Kinetics of Ring-opening Metathesis Polymerization in Ionic Liguid

合成了离子液体负载的钌催化剂,考察了该催化剂在离子液体中对极性环烯烃单体的开环易位聚合(ROMP)反应规律.首先设计合成含离子液体的吡啶配体1,2-二甲基-3-己氧基吡啶六氟磷酸盐咪唑离子液体配体,利用其与Grubbs第二代催化剂配位反应,制备离子液体负载的钌催化剂,通过1H,13CNMR等方法对合成的化合物和催化剂进行表征.催化剂中与钌连接的苯亚甲基上氢(RuCH—Ph)的振动峰由原来Grubbs第二代催化剂的δ19.2移至δ18.6,表明得到了新的催化剂,ICP测定催化剂混合物中纯催化剂的质量分数为36.2%.该催化剂易溶于丙酮、甲醇及咪唑类离子液体等极性溶剂,解决了Grubbs催化剂不溶于离子液体的问题,实现了在纯离子液体中均相ROMP反应.考察了催化剂对极性单体5-羟基环辛烯在离子液体[BMIm]BF4中的ROMP反应规律,研究了离子液体中ROMP反应动力学.

Ring-opening metathesis polymerization （ROMP） is a widespread tool to synthesize well-defined and highly functionalized polymers. The catalyst is a key factor which affects the polymerization behavior. The Grubbs＇ catalysts have good solubility in non-polar solvents such as CH2Cl2, benzene, THF, and toluene, but their solubility in polar solvents such as alcohol, acetone, and ionic liquid is usually very poor, which limited their application for ROMP in polar solvents. In this paper, the pyridyl-based imidazolium salt-supported ruthenium catalyst was synthesized and its use in polymerization of polar cyclooctene derivative in ionic liquid [ BMIm ] BF4 was investigated. The novel pyridyl-based ligand 2,3-dimethyt-1- [ 6- （4-pyridyloxy） hexyl ] imidazol-1-ium hexafluorophosphate was first synthesized, and then the pyridyl ligand coordinated with the second generation Grubbs catalyst to generate the imidazolium salt-supported ruthenium catalyst. The characterizations of the synthesized compounds, the ligand, and the catalyst were undertaken by NMR analyses. In ^1H NMR spectroscopy, the signal of the benzylidene proton shifted from δH19.2 in the second generation Grubbs catalyst upfield to δH 18.6 in the novel catalyst, which meant the ligand exchange had occurred successfully and the novel catalyst formed indeed. The novel imidazolium salt-supported ruthenium catalyst is soluable in CH2Cl2, alcohol, acetone, and ionic liquid, thus, ROMP in pure ionic liquid could be carried out. ROMP of the polar monomer 5-hydroxyl-1-cyclooctene was explored in ionic liquid [ BMIm] BF4. The polymerizations of the monomer performed conveniently under varied reaction conditions, and the conversion of monomer reached to more than 95%. The results also proved that the ionic liquid of [ BMIm] BF4 without group of methyl （-CH3 ） in 2-position couldn＇t result in the poisoning of Grubbs＇ catalyst, and had no influence on the activity of the catalyst. GPC measurement showed the polymer had controlled molecular weight and relatively low molecular weight distribution with polydispersity index of around 1.5. The kinetics of ROMP of the monomer catalyzed by the imidazolium salt-supported ruthenium catalyst in [ BMIm ] BF4 were measured. The plots of In { [ M ] 0/ [ M ] } versus reaction time and Mn versus [ M ] / [ I ] were found to be linear in ionic liquid, and the results showed the polymerization was conducted with controlled/living characteristics. The reaction kinetic equation and reaction active energy for the polymerization process in ionic liquid were also determined, and the results demonstrated the polymerization followed first-order kinetics.