Cyclopentadienyl complexes of uranium(IV) chlorides. Crystal structures of trichloro(η5-cyclopentadienyl)bis(triphenylphosphine oxide)uranium(IV) tetrahydrofuran solvate and of trichloro(η5-cyclopentadienyl)bis(hexamethylphosphoramide)uranium(IV)

Abstract

The crystal and molecular structures of [U(cp)Cl₃(PPh₃O)₂]·thf (thf = tetrahydrofuran)(1) and [U(cp)Cl₃{P(NMe₂)₃O}₂](cp =η⁵-cyclopentadienyl)(2) have been determined from three-dimensional X-ray diffraction data. The compounds crystallize in space groups P2₁/c(1) and P2₁/n(2), with a= 21.725(5), b= 11.699(2), c= 17.269(4)Å, β= 97.9(2)°, and Z= 4 for (1), and a= 9.942(6), b= 32.005(15), c= 9.576(6)Å, β= 106.3(1)°, and Z= 4 for (2). The structures were solved by Patterson and Fourier methods and refined by least squares to final R values of 0.054 for 3 888 independent reflections for (1) and 0.032 for 3 777 independent reflections for (2). In both compounds the uranium atom is octahedrally co-ordinated with the two neutral ligands [PPh₃O and P(NMe₂)₃O] in cis positions; the chlorine atoms are in the mer arrangement and the cyclopentadienyl group is trans to one neutral ligand. The appearance of cis octahedral geometry in complexes of the type [U(cp)Cl₃L₂] is discussed in terms of the operation of a possible trans effect.