Energy-Degeneracy-Driven Covalency in Actinide Bonding

Abstract

Covalent An-Cl bonding in series of +4 actinide hexachlorides, AnCl6 2-(An IV = U, Th, Np, Pu) have been characterized using Cl K-edge XAS and DFT. The results suggest that the 6d-orbital mixing is more substantial than that of the 5f-orbital. Additionally, the results indicate that 5fcovalent bonding with the Cl 3p orbitals is more substantial for Pu than for Th, U, and Np.

Comparison of tetravalent cerium and terbium ions in a conserved, homoleptic imidophosphorane ligand field

“…In particular for oxidation of trivalent lanthanides to tetravalent lanthanides, this variation of the f and d orbital energy and radial extent is crucial since it governs a signicant onset of covalent bonding. 13,14 These two ligand design parametersaccommodating large structural rearrangements and capitalizing on covalency in tetravalent ions are critical for expanding the library of known molecular tetravalent lanthanide complexes. We, and Mazzanti and co-workers, have recently reported the rst tetravalent terbium complexes employing complementary design processes.…”

Tris‐{hydridotris(1‐pyrazolyl)borato}actinide Complexes: Synthesis, Spectroscopy, Crystal Structure, Bonding Properties and Magnetic Behaviour

“…Differences owing to covalency effects are frequently discussed, thus contributing to our understanding of the nature of bonding. [1,2] Severalr eviewsh ave summarised the progress in this field including the annual surveyo no rganometallic chemistry of lanthanides and actinides [3][4][5][6][7][8][9] and the book "Organometallic and CoordinationC hemistry of the Actinides". [10] US colleagues recently reported on the solid-state structure of an Am cyclo-pentadienyl (AmCp 3 )d erivative [11] whereas Evans summarised the lanthanide(II) and actinide(II) chemistry.…”

Charge densities in actinide compounds: strategies for data reduction and model building

“…Participation of the 5f or 6d orbitals (or both) in covalent bonding has been considered for many years, although the amount of covalent character in the highly polar actinide-element bond is still a subject of debate. In contrast to the chemically familiar orbital overlap concept of covalency in light elements, covalency in actinides may be enhanced by small energy differences between metal and ligand orbitals (Su et al, 2018;Ingram et al, 2008;Tanti et al, 2018;Gregson et al, 2016;Kerridge, 2017;Kaltsoyannis, 2013Kaltsoyannis, , 2016Kaltsoyannis, , 2018Jones et al, 2013;Kirker & Kaltsoyannis, 2011;Prodan et al, 2007;Neidig et al, 2013;Kelley et al, 2017). This observation has provoked further debate as to whether 'genuine' covalency ought to increase or decrease across the actinide series.…”