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How 5 f Electron Polarisability Drives Covalency and Selectivity in Actinide N ‐Donor Complexes
Author(s) -
Köhler Luisa,
Patzschke Michael,
Schmidt Moritz,
Stumpf Thorsten,
März Juliane
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202102849
Subject(s) - isostructural , ligand (biochemistry) , chemistry , covalent bond , crystallography , stereochemistry , pyrrole , actinide , crystal structure , inorganic chemistry , organic chemistry , biochemistry , receptor
We report a series of isostructural tetravalent actinide (Th, U−Pu) complexes with the N ‐donor ligand N , N’ ‐ethylene‐bis((pyrrole‐2‐yl)methanimine) (H 2 L , H 2 pyren). Structural data from SC‐XRD analysis reveal [An(pyren) 2 ] complexes with different An−N imine versus An−N pyrrolide bond lengths. Quantum chemical calculations elucidated the bonding situation, including differences in the covalent character of the coordinative bonds. A comparison to the intensely studied analogous N,N′‐ ethylene‐bis(salicylideneimine) (H 2 salen)‐based complexes [An(salen) 2 ] displays, on average, almost equal electron sharing of pyren or salen with the An IV , pointing to a potential ligand‐cage‐driven complex stabilisation. This is shown in the fixed ligand arrangement of pyren and salen in the respective An IV complexes. The overall bond strength of the pure N ‐donor ligand pyren to An IV (An=Th, U, Np, Pu) is slightly weaker than to salen, with the exception of the Pa IV complex, which exhibits extraordinarily high electron sharing of pyren with Pa IV . Such an altered ligand preference within the early An IV series points to a specificity of the 5 f 1 configuration, which can be explained by polarisation effects of the 5 f electrons, allowing the strongest f electron backbonding from Pa IV (5 f 1 ) to the N donors of pyren.