Synthesis of the Uranium Triflates U(OTf)3 and U(OTf)4 – Crystal Structure of [U(OTf)2(OPPh3)4][OTf]

Reactions of pure triflic acid (TfOH) with UH3 at 20 °C and with U or UCl3 at 120 °C afforded U(OTf)3 (1), which was transformed into U(OTf)4 (2) by reaction with TfOH at 180 °C; 2 was also synthesized by treating UCl4 with TfOH at 120 °C. The yields were in excess of 90%. The crystal structure of [U(OTf)2(OPPh3)4][OTf] (3) was determined, which revealed a seven-coordinate uranium(III) centre bound by monodentate and bidentate triflate ligands.