Covalency in the f Element−Chalcogen Bond. Computational Studies of M[N(EPR₂)₂]₃ (M = La, Ce, Pr, Pm, Eu, U, Np, Pu, Am, Cm; E = O, S, Se, Te; R = H, ⁱPr, Ph)

Abstract

The geometric and electronic structures of the title complexes have been studied using scalar relativistic, gradient-corrected density functional theory. Extension of our previous work on six-coordinate M[N(EPH 2) 2] 3 (M = La, Ce, U, Pu; E = O, S, Se, Te), models for the experimentally characterized M[N(EP (i)Pr 2) 2] 3, yields converged geometries for all of the other 4f and 5f metals studied and for all four group 16 elements. By contrast, converged geometries for nine-coordinate M[N(EPPh 2) 2] 3 are obtained only for E = S and Se. Comparison of the electronic structures of six- and nine-coordinate M[N(EPH 2) 2] 3 suggests that coordination of the N atoms produces only minor changes in the metal-chalcogen interactions. Six-coordinate Eu[N(EPH 2) 2] 3 and Am[N(EPH 2) 2] 3 with the heavier group 16 donors display geometric and electronic properties rather different from those of the other members of the 4f and 5f series, in particular, longer than expected Eu-E and Am-E bond lengths, smaller reductions in charge difference between M and E down group 16, and larger f populations. The latter are interpreted not as evidence of f-based metal-ligand covalency but rather as being indicative of ionic metal centers closer to M (II) than M (III). The Cm complexes are found to be very ionic, with very metal-localized f orbitals and Cm (III) centers. The implications of the results for the separation of the minor actinides from nuclear wastes are discussed, as is the validity of using La (III)/U (III) comparisons as models for minor actinide/Eu systems.

Defect Induced Electronic Structure of Uranofullerene

“…A significant advantage of DFT calculations is that accounting for the electron correlation does not increase the CPU time considerably. Therefore, DFT has been widely used in the calculation of actinides31323334. Relativistic pseudopotential method is able to incorporate relativistic effects with a small increase in computational time3536.…”

Covalency in CeIV and UIV Halide and N‐Heterocyclic Carbene Bonds

“…Examples include studies of the bonding in 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine complexes of Cm III and Eu III , [43] backbonding in the Nd III and U III carbonyl complexes F 3 MCO, [44] and our own work assessing both the extent and origin (f vs. d) of covalency in imidodiphosphinochalcogenide complexes. [4,12] We have previously described the synthesis of saturated backbone NHC proligands, OCMe 2 CH 2 (CHNCH 2 CH 2 NR) (R = iPr, 2,6-iPrC 6 H 3 , 2,4,6-MeC 6 H 2 ), and their complexes with both low-and high-valent f-block cations. [45,46] Herein we report a new one-electron oxidation route to the synthesis of Ce IV and U IV starting materials and halide complexes, and the DFT computational comparison of the bonding in these two M IV complexes supported by an NHC ligand.…”

“…While there is some evidence that the 6d orbitals may be more appropriately considered as valence in the NPA scheme, [68] we have no direct experience with such a partitioning and have decided to retain the default approach so as to better facilitate comparison with our previous studies of related systems. [4,12,56] …”

Triamidoamine thorium-arsenic complexes with parent arsenide, arsinidiide and arsenido structural motifs

“…12), remains extremely rare13. However, in order to truly delineate bonding trends across the actinides, and thus draw inferences as to their competitive bonding and reactivity, comparisons between structurally analogous complexes that contain different actinide metals are required, but concerted comparisons of such families of compounds remain relatively rare1415161718192021 due to a paucity of synthetic methodologies to prepare them or the radiological limitations encountered in this area. In this regard, thorium is an attractive element to study, both in terms of radiological practicality and also the nature of its bonding when compared to uranium, that is, 6d versus 5f character1921222324, respectively.…”