The crystal structure of uranium chloride π-tricyclopentadienyl

Actinide Organometallic Complexes with π-Ligands

Recent developments and results from the organometallic chemistry of the actinides are reviewed. In the last one and a half years the structural data of about 15 organometallic complexes of transuranium actinides (Np or Pu) have been published, all involving π-ligands in the coordination sphere of the metal ion. On the basis of these data, a comparison of these molecules is presented. Depending on the steric demands of the ligands, effects like the actinide contraction seem to be stronger or weaker in the structural features. This indicates that the interplay between the actinide ion and the π-ligand is rather flexible, enabling the formation of stable bonds over a broad range of actinide ion oxidation states.

The Renaissance of Non-Aqueous Uranium Chemistry

Prior to the year 2000, non-aqueous uranium chemistry mainly involved metallocene and classical alkyl, amide, or alkoxide compounds as well as established carbene, imido, and oxo derivatives. Since then, there has been a resurgence of the area, and dramatic developments of supporting ligands and multiply bonded ligand types, small-molecule activation, and magnetism have been reported. This Review 1) introduces the reader to some of the specialist theories of the area, 2) covers all-important starting materials, 3) surveys contemporary ligand classes installed at uranium, including alkyl, aryl, arene, carbene, amide, imide, nitride, alkoxide, aryloxide, and oxo compounds, 4) describes advances in the area of single-molecule magnetism, and 5) summarizes the coordination and activation of small molecules, including carbon monoxide, carbon dioxide, nitric oxide, dinitrogen, white phosphorus, and alkanes.

Benchmark study of the Mössbauer isomer shifts of Eu and Np complexes by relativistic DFT calculations for understanding the bonding nature of f-block compounds

Ten Eu and ten Np benchmark complexes were calculated by relativistic all-electron DFT. The B2PLYP functional showed good correlation with the Mössbauer experiment for both Eu and Np systems.

Reductive assembly of cyclobutadienyl and diphosphacyclobutadienyl rings at uranium

Despite the abundance of f-block-cyclopentadienyl, arene, cycloheptatrienyl and cyclo-octatetraenide complexes, cyclobutadienyl derivatives are unknown in spite of their prevalence in the d-block. Here we report that reductive [2+2]-cycloaddition reactions of diphenylacetylene and (2,2-dimethylpropylidyne)phosphine with uranium(V)-inverted sandwich 10π-toluene tetra-anion complexes results in the isolation of inverted sandwich cyclobutadienyl and diphosphacyclobutadienyl dianion uranium(IV) complexes. Computational analysis suggests that the bonding is predominantly electrostatic. Although the ψ4 molecular orbital in the cyclobutadienyl and diphosphacyclobutadienyl ligands exhibits the correct symmetry for δ-bonding to uranium, the dominant covalent contributions arise from π-bonding involving ψ2 and ψ3 orbital combinations. This contrasts with uranium complexes of larger arenes and cyclo-octatetraenide, where δ-bonding dominates. This suggests that the angular requirements for uranium to bond to a small four-membered ring favours π-bonding, utilizing 5f- instead of 6d-orbitals, over δ-bonding that is favoured with larger ligands, where 6d-orbitals can become involved in the bonding.

Studies of U(C5H5)3Cl: II-Temperature dependence of the molecular configurations

The structure of uranium tris(cyclopentadienyl)chlorine [U(C5H5)3]Cl [Mr = 468.45, Z = 4, Dx = 2.194 g/cc] exhibits two phase transitions between 5 K and 300 K. In this paper we discuss the crystallographic structures, which show a transition at 245 K from the centrosymmetric space group P21/n at 300 K to the non-centrosymmetric space group P n observed at 120 K; below 78 K the structure becomes triclinic

Studies of U(C5H5)3Cl: I-Evidence for structural phase transitions below room temperature

We have used neutron and X-ray diffraction techniques on both single crystal and polycrystalline samples to examine the symmetry of the unit cell of the organometallic compound uranium tris(cyclopentadienyl)chlorine, U(C5H5)3Cl, as a function of temperature below 300 K. Two phase transitions occur. The first, at 245 K, results in a change of space group but the monoclinic symmetry is retained; the second, at 78 K, results in the material becoming triclinic. Important differences are observed between the results obtained with neutron and X-ray diffraction; the latter fail to show clear evidence for the transition at 78 K. We believe this is a consequence of the different penetration depths of the two radiations. Calorimetric data confirms the presence of the 245 K transition.