Synthesis Of Ionic Liquid-Supported Ruthenium Complex And Ring-Opening Metathesis Polymerization Of Cycloolefin

Ring-opening metathesis polymerization (ROMP) is a widespread tool to synthesize well-defined and highly functionalized polymers. The catalyst is an important factor which affects the ROMP of monomers. The Grubbs'catalysts have good solubility in non-polarity solvents such as CH₂Cl₂, benzene, and toluene, but their solubility in polar solvent such as alcohol and ionic liquid was very poor, which limited their application for ROMP in polar solvents. In this paper, the imidazolium salt-supported ruthenium catalyst was synthesized and its use in polymerization of polar cycloolefins in ionic liquid [BMIm]BF4 was investigated.The novel pyridyl ligand 2,3-dimethyl-1-[2-(4-pyridyloxy)ethyl] imidazol-1-ium hexafluorophosphate was first synthesized.The pyridyl ligand coordinated with the second generation Grubbs'catalyst to get the imidazolium salt-supported ruthenium catalyst . The characterization of the synthesized compounds, the ligand, and the catalyst was carried out by IR, NMR, XRD and elemental analysis. In ¹H NMR spectroscopy, the signal of the benzylidene proton shifts from δ_h=19.2 ppm in the second generation Grubbs'catalyst to δ_h=16.3 ppm in the novel catalyst. In ³¹P NMR spectroscopy, the signal of PCy₃ disappeared, which demonstrated the group of PCy₃ was replaced by the other ligand completely.The single crystal of the pyridyl ligand 2,3-Dimethyl-1-[2-(4-pyridyloxy)ethyl] imidazol-1-ium hexafluorophosphate was obtained. The crystal is monoclinic, with the parameters as: P2_1/c, a=12.469(5) A, b = 16.470(7) A, c = 7.943(3) A, β= 106.691(5)°, V= 1562.5(11) A³, Dx= 1.544 Mg/m³.The novel imidazolium salt-supported ruthenium catalyst are soluable in ionic liquid, thus, ROMP in pure ionic liquid can be carried out. The ROMP of cycloolefins, especially the polar monomer 5-norbornene-2-carbonitrile was explored in ionic liquid [BMIm]BF4. The polymerization of the monomer processed successfully, the conversion reached 52 %, which was much higher than that using the non-supported NHC/pyridine ruthenium catalyst. The result also proved that the imidazolium salt without -CH₃ in 2-position couldn't result in the poisoning of Grubbs'catalyst, and had no influence on the activity of the catalyst.