The reaction of the trivalent lanthanide triflates Ln(OTf)3 (Ln = Sm, Eu; OTf = CF3SO3-) with the respective metals in acetonitrile leads to the Ln(II)-triflates Eu(OTf)2(CH3CN) (monoclinic, P21/n, Z = 4, a = 1053.54(1), b = 610.28(5), c = 1946.92(2) pm, b = 98.611(4)) and Sm(OTf)2(CH3CN) (monoclinic, P21/n, Z = 4, a = 1054.41(4), b = 612.16(2), c = 1952.65(7) pm, b = 98.524(2)). The isotypic strontium compound Sr(OTf)2(CH3CN) (monoclinic, P21/n, Z = 4, a = 1056.39(5), b = 610.05(3), c = 1950.1(1) pm, b = 98.900(2)°) has been obtained from SrCO3 and triflic acid. The compounds have been investigated by X-ray diffraction, vibrational spectroscopy, luminescence spectroscopy, cyclic voltammetry, thermal analysis, and magnetic measurements.