Synthesis, structural and spectroscopic characterisation of three di-μ-fluoro-bis[dioxouranyl] complexes

Three novel uranyl complexes with organic phosphine oxide ligands and bridging fluorides have been synthesised and structurally characterised. In [{UO2(mu-F)(TPPO)(3)}(2)][BF4](2) . C6H14, 1, and [{UO2(-muF)(TBPO)(3)}(2)][BF](2) 2, (where TPPO and TBPO are triphenylphosphine oxide and tri-n-butylphosphine oxide, respectively) two {UO2}(2+) moieties are bridged by two fluorides with three additional terminal P=O donor ligands coordinated to each uranium centre. The dicationic complexes are both charge balanced by two uncoordinated tetrafluoroborate anions. In the related structure, [UO2(mu-F)(F)(DPPMO2)](2) . 2MeOH (3), terminal fluoride is also coordinated to both uranyl centres (where DPPMO2 = bis(diphenylphosphine oxide)methane). All three complexes were prepared during attempted syntheses of complexes with tetrafluoroborate directly coordinated to uranium. It is clear from these results that the fluorophilicity of {UO2}(2+) causes the abstraction of fluoride from [BF4](-), with the weakly coordinating anion only present as a counter cation in 1 and 2, and absent completely in 3. (C) 2004 Elsevier Ltd. All rights reserved.