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Abstract: The solubility of carbon dioxide in room temperature ionic liquids (RTILs), dialkylimidazolium dialkylphosphates, was measured at 313–333K and at pressures close to atmospheric pressure, from which Henry''s law coefficients, standard Gibbs free energy, enthalpy, and entropy changes of solvation were derived. The CO2 solubility in the dialkylimidazolium dialkylphosphate was found to increase with increasing chain length of the alkyl groups on the cation and/or the anion as was similarly found in other RTILs. Among various dialkylimidazolium dialkylphosphates tested, 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][Et2PO4]) and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][Bu2PO4]) exhibited the comparable or better capability of dissolving CO2 in comparison with that of [BMIM][BF4], but their absorption capacities were still lower than that of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). [Copyright &y& Elsevier]

Abstract: A series of ionic liquid-based zinc tetrahalide complexes were synthesized and their effects in the coupling reactions of ethylene oxide (EO) and carbon dioxide to produce ethylene carbonate (EC) were evaluated. The zinc tetrahalide complexes displayed high catalytic activities for the coupling reaction, but were found to cause a severe decomposition of EC during the vacuum-distillation of the product mixture. Among the various factors affecting the EC decomposition, the concentration of zinc tetrahalide species was most responsible for the decomposition: the lower the concentration, the lesser the decomposition. The addition of an imidazolium or ammonium halide was effective for enhancing the activity of the zinc tetrahalide complex while having only a minor effect on the decomposition rate. The optimum catalyst composition was discussed for producing EC feasibly with minimized product decomposition. [Copyright &y& Elsevier]

Abstract: Phosphine adducts of zinc(II) halides, ZnX2L2 (X=Cl, Br, I; L=PMe2Ph, PEt3, PBu3, PPh3, PCy3), prepared by the reaction of ZnX2 with two equivalents of corresponding phosphines, showed high activities for the coupling reaction of CO2 and ethylene oxide to produce ethylene carbonate. The catalytic activity of ZnX2L2 was hardly affected by the nucleophilicity of the phosphine ligands, with the exception of ZnX2(PCy3)2, but depended strongly on the nature of halide ligands. An active species containing ethoxyphosphonium ligands, Zn3Br6[μ-OCH2CH2-P(C6H5)3]3, was isolated and characterized by X-ray crystallography, elemental analysis, and NMR spectroscopy. The mechanistic pathway for the formation of active species and cyclic carbonates is discussed. [Copyright &y& Elsevier]