Molecular Adducts of Inorganic Salts. VI. The Dimorphism of Cd(ReO4)2.2tu (tu = Thiourea)

Dimeric uranyl complexes with bridging perrhenates

The reaction between [UO2(ReO4)2.H(2)O] and two equivalents of either tri-n-butyl phosphine oxide (TBPO) or tri-iso-butyl phosphate (TiBP) results in the formation of [UO2(mu2-ReO4)(ReO4)(TBPO)2]2 (1) and [UO2(mu2-ReO4)(ReO4)(TiBP)2]2 (2) respectively. Both complexes crystallise as two structurally similar centrosymmetric dimers, the cores containing two uranyl moieties linked by bridging perrhenates. Two P=O donor ligands and one monodenatate perrhenate complete the pentagonal bipyramidal coordination sphere at each metal centre. Both complexes have also been characterised in the solid state by vibrational and absorption spectroscopy. Solution spectroscopic characterisation indicates that both perrhenate and phosphine oxide (1) or phosphate (2) remain coordinated, although it is not possible to state conclusively that the dimeric species remain intact. A low resolution structural study of a minor product from the reaction that yielded revealed a monomeric complex with only monodentate perrhenate coordination, [UO2(ReO4)2(H2O)(TiBP)2] (2'). These results represent the first structural evidence for the bridging coordination mode of perrhenate on coordination to an actinide and yields further insight into the possible solvent phase pertechnetate complexes that may exist in PUREX process phosphate rich solvent.

Synthesis and Characterization of ReO4-Containing Microporous and Open Framework Structures

A microporous and an open framework structure, [Cu(2)(pzc)(2)(H(2)O)(2)ReO(4)] (I) and [Cu(pzc)(H(2)O)ReO(4)].2H(2)O (II) (pzc = 2-pyrazinecarboxylate), respectively, have been prepared using hydrothermal methods and characterized using IR, TGA, and X-ray diffraction (I Pnma, No. 62, Z = 4, a = 7.4949(9) A, b = 24.975(3) A, c = 9.141(1) A; II P2(1)/c, No. 14, Z = 4, a = 8.5878(9) A, b = 12.920(1) A, c = 9.741(1) A, beta = 92.830(2) degrees ). I and II crystallize as red and blue solids, respectively, and each contains chains constructed from alternating Cu(pzc)(2)/ReO(4) oxide-bridged metal sites. The bidentate pzc ligand further bridges each -Cu-O-Re-O- chain to adjacent chains, via the Cu sites, to form a 3D net in I, with ellipsoidal channels that are approximately 3.3-4.7 A x 12.5 A, and in II, stacked layers of square nets with H(2)O-filled cavities that are approximately 4.4 x 5.1 A. Local ReO(4)(-) groups, a component of common oxidation catalysts, are directed at the channels and cavities of each structure, respectively. Thermogravimetric analysis indicates that I loses up to 64% of its H(2)O content before decomposition at 225 degrees C, while II loses approximately 100% of its H(2)O content by 265 degrees C.