Treatment of [Ln(BH 4) 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(BH 4) 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.