Treatment of DyCl 3 (H 2 O) 6 with thionyl chloride in the presence of tetrahydrofuran provided colourless crystals of DyCl 3 (THF) 3.5 , subsequently identified as the ionic salt [trans-DyCl 2 (THF) 5 ] [trans-DyCl 4 (THF) 2 ] by an X-ray diffraction study. The dysprosium atom in the monocation is seven coordinate with the trans-DyCl 2 unit [Dy-Cl, 2.624(5)A˚] surrounded by five tetrahydrofuran molecules (Dy-O, mean 2.41(2)A˚) in a regular pentagonal bipyramidal geometry. For the anion the dysprosium atom is six coordinate with an octahedral geometry comprising four equatorial chlorine atoms (Dy%z.sbnd;Cl, mean 2.642(5)A˚) and two axial tetrahydrofuran molecules (Dy-O, 2.41(2)A˚).