Single-crystal growth and solid-state characterization of two new 2-methylimidazolium oxalate salts

Abstract Mixtures of aqueous solutions of 2-methylimidazole and oxalic acid, in molar ratios of 1:2 and 2:1, were investigated, leading to the isolation of two 2-methyl-1 H -imidazol-3-ium (2-methylimidazolium) oxalate salts. Compound [C 4 H 7 N 2 ][0.5C 2 O 4 ][H 2 C 2 O 4 ][H 2 O] ( 1 ) was isolated as a co-product in the presence of trimethyltin chloride, whereas [(C 4 H 7 N 2 ) 2 ][C 2 O 4 ] ( 2 ) was obtained directly from the aqueous reaction. Both compounds were characterized by FT-IR spectroscopy, Hirshfeld surface analysis, elemental analysis and single-crystal X-ray diffraction. Salt 1 crystallizes in the monoclinic system, space group C 2/ c , with unit cell parameters a = 24.682(4), b = 3.7589(7), c = 22.829(4) Å, β = 113.486(4)°, V = 1,942.5(6) Å 3 and Z = 8. The four components of 1 , 2-methylimidazolium cations, oxalate anions, oxalic acid and water are connected through intermolecular hydrogen bonds. Salt 2 crystallizes in the orthorhombic system, space group Pbca , with a = 13.9808(9), b = 13.3039(10), c = 19.6563(13) Å, V = 3,656.1(4) Å 3 and Z = 12. Two 2-methylimidazolium cations compensate for the two negative charges of an oxalate anion. The packing of the building units in the two salts features the propagation of a three-dimensional network in 1 , whereas in 2 it is restricted to a layered arrangement.