New BEDT-TTF Salts Incorporating the Hydrogen Dichloride (HCl₂^-) Anion

Salts of the π-donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) have been isolated with hydrogen dichloride (HCl 2 - ) as the counterion. Two phases were obtained, α‘-BEDT-TTF 2 (HCl 2 ) (1) and ε-BEDT-TTF(HCl 2 ) (2), by electrocrystallization from solvent mixtures containing ClCH 2 COCl. Like previously described α‘-BEDT-TTF 2 X salts, 1 contains sheets of twisted BEDT-TTF dimers, and conductivity and magnetic susceptibility are consistent with a description of nearly localized (BEDT-TTF) 2 + radicals. Salt 2, space group C 2/ m, undergoes an anion ordering structural phase transition near 200 K, resulting in a new low-temperature phase ε‘-BEDT-TTF(HCl 2 ) (3) with space group P 2 1 / c . Below 170 K, 3 undergoes a magnetic phase transition seen in electron paramagnetic resonance data. The HCl 2 - ion is linear in 1 but bent in 2 and 3 . α‘-(BEDT-TTF) 2 (HCl 2 ), 1, crystallizes in the P 2/ c space group with a = 7.7023(1) Å, b = 6.6140(1) Å, c = 30.1077(6) Å, β = 96.506(1)°, V = 1523.90(4) Å 3, and Z = 2. ε-BEDT-TTF(HCl 2 ), 2, crystallizes in the C 2/ m space group with a = 12.9687(8) Å, b = 11.6077(8) Å, c = 5.6949(4) Å, β = 104.688(1)°, V = 829.28(10) Å 3, and Z = 2. ε‘-BEDT-TTF(HCl 2 ), 3, belongs to the P 2 1 / c space group with a = 12.7112(1) Å, b = 11.5778(2) Å, c = 11.3583(1) Å, β = 101.194(1)°, V = 1639.77(3) Å 3, and Z = 4.