Synthesis of novel ionic liquid ([C₄CNmim]⁺PF₆ ⁻) and application to preparation of polyketone

Abstract

N-valeronitrile-N′-methylimidazolium hexafluorophosphate ([C₄CNmim]⁺PF₆ ⁻), as a novel ionic liquid with polar nitrile functional group, was prepared. The structure of the ionic liquid was characterized by using IR and ¹H NMR. As a medium, the ionic liquid plays an important role in copolymerization of carbon monoxide (CO) with styrene (St). Some synthetic conditions were determined, including the usage of ionic liquid, palladium composite catalyst and methanol, CO pressure, reaction time and reaction temperature. The influence of these factors on catalytic activity was analyzed. The results show that the catalytic activity has reached 1 724.1 gStCO/(gPd·h) and the catalyst could be reused 5 times under the optimal condition: composite catalyst 0.015 mmol, ionic liquid 3 mL, methanol 0.75 mL, CO pressure 2 MPa, reaction time 2 h and reaction temperature 70 °C. This CO/St copolymerization within [C₄CNmim]⁺PF₆ ⁻ system could facilitate ionic liquids with efficient and economical applications to polymeric materials.

Keywords

nitrile ionic liquid / polyketone / synthetic condition / carbon monoxide / styrene

References

[1] Drent E., Budzelaar P. H. M. Palladium-catalyzed alternating copolymerization of alkenes and carbon monoxide[J]. Chemical Reviews, 1996, 96(2): 663-682.

[2] Smaardijk A A, Drent E. Polyketones: Aliphatic[J]. Encyclopedia of Materials: Science and Technology, 2008: 7194–7196.

[3] Bianchini C., Meli A. Alternating copolymerization of carbon monoxide and olefins by single-site metal catalyst[J]. Coordination Chemistry Reviews, 2002, 225(1/2): 35-66.

[4] Marszałł M. P., Markuszewski M. J., Kaliszan R. Separation of nicotinic acid and its structural isomers using 1-ethyl-3-methylimidazolium ionic liquid as a buffer additive by capillary electrophoresis[J]. Journal of Pharmaceutical and Biomedical Analysis, 2006, 41(1): 329-332.

[5] Welton T. Room-temperature ionic liquids: Solvents for synthesis and catalysis[J]. Chemical Reviews, 1999, 99(8): 2071-2084.

[6] Wasserscheid P., Keim W. Ionic liquid-New “solvents” transition metal catalysis[J]. Angewandte Chemie International Edition, 2000, 39(21): 3772-3789.

[7] Cheng L., Zhang Y. M., Zhao T. T., et al. Free radical polymerization of acrylonitrile in green ionic liquids[J]. Macromolecular Symposia, 2004, 216(1): 9-16.

[8] Guo J. T., Gao S., Feng Y. K., et al. Study on copolymerization of CO/Styrene with [CH₃C₄Py]⁺PF₆ ⁻ as novel reaction medium[J]. Research Journal of Chemistry Environment, 2010, 14(2): 7-16.

[9] Zhao D. B., Fei Z. F., Scopelliti R., et al. Synthesis and characterization of ionic liquids incorporating the nitrile functionality[J]. Inorganic Chemistry, 2004, 43(6): 2197-2205.

[10] Wu X. H., Yang Z. C., Qin W., et al. Synthesis of 4,4′-dimethyl-2,2′-bipyridine catalyzed by Pd/C[J]. Chinese Journal of Organic Chemistry, 2006, 26(2): 260-262.

[11] Milani B., Anzilutti A., Vicentini L., et al. Bis-chelated palladium(II) complexes with nitrogen-donor chelating ligands are efficient catalyst precursors for the CO/styrene copolymerization reaction[J]. Organometallics, 1997, 16(23): 5064-5075.

[12] Guo J. T., Liu B., Wang X. Y., et al. The use of ion exchange resins in the recycle of palladium catalysts for the synthesis of polyketones[J]. Reactive & Functional Polymers, 2004, 61(2): 163-170.