DIALKYLIMIDAZOLIUM-SODIUM CHLOROALUMINATE TERNARY SALT SYSTEM - PHASE-DIAGRAM AND CRYSTAL-STRUCTURE

The phase diagram of the buffered neutral aluminum chloride + 1-ethyl-3-methyl-1H-imidazolium chloride + sodium chloride (AlCl3-EMIC-NaCl) ternary melt system can be represented by a binary phase diagram composed of (EMI)AlCl4 and NaAlCl4. In the binary phase diagram, the salts are liquid at, or near, room temperature for a wide range of compositions. At the 1 : 1 composition, the congruently melting compound (EMI)(Na)(AlCl4)2 with m.p. = 36.7-degrees-C is formed. Crystals of this mixed organic-inorganic salt were grown for single crystal x-ray diffraction analysis. The compound crystallizes in the space group P1BAR with lattice parameters a = 10.321(1) angstrom, b = 10.895(3) angstrom, c = 9.284(4) angstrom, alpha = 98.31(2)-degrees, beta = 100.83(4)-degrees, gamma = 101.95(3)-degrees. Data collected at -120-degrees-C gave final residuals of R = 0.037 and R(w) = 0.045 using 2713 observed reflections. The packing diagram reveals Na+ ion zig-zag chains running along the a-axis with each Na+ surrounded by four AlCl4- units, reminisecent of NaAlCl4. The AlCl4- ions form a distorted square planar coordination sphere around Na+ at an average Na-Al distance of 3.76(4) angstrom. Using a sodium ionic radius of 1.16 angstrom, a new AlCl4- ionic radius of 2.60 angstrom is calculated. This radius is 0.21 angstrom shorter than the reported thermodynamic radius.