Treatment of [Ln(BH4)(3)(THF)(3)] (Ln = Ce, Nd) with 3 and 4 mol equiv of KSBT in tetrahydrofuran (THF) led to the formation of [Ln(SBT)(3)(THF)] and [K(THF)Ln(SBT)(4)], respectively. The uranium(IV) compound [U(SBT)(4)(THF)(2)] was obtained from U(BH4)(4) and was reversibly reduced by sodium amalgam into the corresponding anionic uranium(III) complex. The crystal structures of [Ln(SBT)(3)(THF)(2)] (Ln = Ce, Nd), [K(15-crown-5)(2)][Nd(SBT)(4)], [U(SBT)(4)(THF)], and [K(15-crown-5)(2)][U(SBT)(4)(py)] show the bidentate coordination mode and the thionate character of the SBT ligand.