The structural and spectroscopic characterisation of three actinyl complexes with coordinated and uncoordinated perrhenate: UO2ReO42TPPO3, UO2TPPO32µ2-O2ReO42and NpO2TPPO4ReO4Electronic supplementary information (ESI) available: Mid-infrared ATR and Raman spectra. See http://www.rsc.org/suppdata/dt/b3/b313045b/

The first structural characterization of an actinide complex with coordinated perrhenate is reported, UO2ReO42TPPO31. In this UO22complex two ReO4−anions and three TPPO triphenylphosphine oxide PO donor ligands are coordinated in the equatorial plane in a cisoidarrangement. This bonding arrangement, and apparent strain observed in the equatorially bonded ligands, is attributed to the solid state packing in adjacent molecules in which hydrophobic TPPO ligands form an effective “shell” around a hydrophilic core of two UO2ReO42moieties. Solid state vibrational spectroscopy infrared and Raman, 31P CP MAS NMR and elemental analysis are also consistent with the formula of 1. Solution state vibrational spectroscopy and 31P NMR measurements in EtOH indicate the lability of the TPPO and ReO4−groups. The photolytic generation of peroxide in EtOH solutions of 1leads to the formation of trace quantities of UO2TPPO32µ2-O2ReO42, 2, in which the coordinated ReO4−groups of 1have been displaced by bridging O22−, derived from atmospheric O2. Finally, attempts to synthesise a NpO2analogue of 1have resulted only in the formation of NpO2TPPO4ReO4, 3, in which ReO4−acts solely as a counter anion. From these results it can be concluded that ReO4−will bond to UO22, but will be readily displaced by a more strongly coordinating ligand e.g.peroxide and will not coordinate to an actinyl cation with a lower charge, NpO2, under the same reaction conditions.