Lanthanoid-Based Ionic Liquids Incorporating the Dicyanonitrosomethanide Anion

A series of low-melting-point salts with hexakisdicyanonitrosomethanidolanthanoidate anions has been synthesised and characterised: (C2mim)3[Ln(dcnm)6] (1?Ln; 1?Ln=1?La, 1?Ce, 1?Pr, 1?Nd), (C2C1mim)3[Pr(dcnm)6] (2?Pr), (C4C1pyr)3[Ce(dcnm)6] (3?Ce), (N1114)3[Ln(dcnm)6] (4?Ln; 4?Ln=4?La, 4?Ce, 4?Pr, 4?Nd, 4?Sm, 4?Gd), and (N1112OH)3[Ce(dcnm)6] (5?Ce) (C2mim=1-ethyl-3-methylimidazolium, C2C1mim=1-ethyl-2,3-dimethylimidazolium, C4C1py=N-butyl-4-methylpyridinium, N1114=butyltrimethylammonium, N1112OH=2-(hydroxyethyl)trimethylammonium=choline). X-ray crystallography was used to determine the structures of complexes 1?La, 2?Pr, and 5?Ce, all of which contain [Ln(dcnm)6]3- ions. Complexes 1?Ln and 2?Pr were all ionic liquids (ILs), with complex 3?Ce melting at 38.1?degrees C, the lowest melting point of any known complex containing the [Ln(dcnm)6]3- trianion. The ammonium-based cations proved to be less suitable for forming ILs, with complexes 4?Sm and 4?Gd being the only salts with the N1114 cation to have melting points below 100?degrees C. The choline-containing complex 5?Ce did not melt up to 160?degrees C, with the increase in melting point possibly being due to extensive hydrogen bonding, which could be inferred from the crystal structure of the complex.