COMPLEXES OF A HEXADENTATE PODAND LIGAND WITH ACTINIDES - THE SYNTHESES AND CRYSTAL-STRUCTURES OF [TH(TP(PY))(NO3)(3)].(DMF).(ET(2)O)(0.5) AND TRANS-[UO2(TP(PY))(OET)] (PY)=TRIS[3-(2'-PYRIDYL)-PYRAZOL-1-YL]HYDROBORATE)

The syntheses and crystal structures of [Th(Tp(Py))(NO3)(3)] (1) and t rans-[UO2(Tp(PY))(OEt)] (2) are described, where [Tp(Py)](-) is the po tentially hexadentate podand ligand tris[3-(2'-pyridyl)-pyrazol-1-yl]h ydroborate. In the crystal structure of (1) (dmf).(Et(2)O)(0.5) the Th (IV) centre lies within the encapsulating ligand cavity, and is 12-coo rdinate from the six N-donor atoms of [Tp(Py)](-) and three bidentate nitrate ligands. The molecule has crystallographically imposed threefo ld rotational symmetry, and the nitrate ions are interleaved between t he bidentate arms of the podand. In contrast for (2), where it is ster ically impossible for the trans-dioxouranium(IV) fragment to be wholly encapsulated, the coordination geometry is pentagonal bipyramidal. Th e pentagonal plane comprises two bidentate ligand arms and one ethoxid e ligand; the third ligand arm is pendant.