Gold compounds as ionic liquids. Synthesis, structures, and thermal properties of N,N '-dialkylimidazolium tetrachloroaurate salts

The salts [C6H11N2][AuCl4] (1) and [C8H15N2][AUC(14)] (2) ([C6H11N2](+) = 1 -ethyl-3-methylimidazolium; [C8H15N2](+) 1- butyl-3-methylimidazolium), pre pared by a solvent-free method, display similar crystal structures. 1 cryst allizes in the monoclinic P2(1)/e space group (a = 11.1915(15) Angstrom, b = 12.380(2) Angstrom, c = 9.2883(13) Angstrom; beta 98.810(16)degrees; Z = 4) and 2 in the triclinic P (1) over bar space group (a = 7.9354(14) Angstr om, b = 8.3930(15) A, c = 11.397(2) Angstrom; a 83.94(2)degrees, beta = 87. 93(2)degrees, gamma = 78.04(2)degrees; Z = 2). In both cases, a unique moti f is seen consisting of linear chains of alternating comer-to-face arranged [AuCl4](-) ions at A...Cl separations of 3.356(3) Angstrom (1) and 3.452(3 ) Angstrom (2). Ionic liquid behavior is observed from 58 to 220 degrees C, for 1 and 50 to 250 degrees C for 2.