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Bonding Trends in Tetravalent Th-Pu Monosalen Complexes
Thomas Radoske1, Juliane März1, Michael Patzschke1
1Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstrasse 400, 01328, Dresden, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|September 9, 2020
Summary
Researchers synthesized actinide complexes to study their bonding with N-donor molecules. Quantum chemical calculations confirmed that actinide-oxygen bonds exhibit significant covalent character, unlike actinide-nitrogen and actinide-chlorine bonds.
Area of Science:
- Inorganic Chemistry
- Actinide Chemistry
- Coordination Chemistry
Background:
- Early actinides (Th, U, Np, Pu) form complexes with N,N'-bis(salicylidene)ethylenediamine (salen) and pyridyl ligands (Pyx).
- Understanding the bonding preferences of heavy elements is crucial for nuclear fuel cycles and waste management.
Purpose of the Study:
- To synthesize and characterize novel tetravalent early actinide complexes.
- To investigate the bonding affinity of early actinides for small neutral N-donor molecules.
- To elucidate the nature of bonding (ionic vs. covalent) in these complexes.
Main Methods:
- Synthesis of [AnCl2(salen)(Pyx)2] complexes (An=Th, U, Np, Pu; Pyx=pyridine, 4-methylpyridine, 3,5-dimethylpyridine).
- Structure determination using single-crystal X-ray diffraction (XRD).
- Characterization of bulk powders via infrared spectroscopy.
- Quantum chemical calculations to support experimental findings.
Main Results:
- Isostructural series of complexes were synthesized and characterized.
- Trends in interatomic distances (An-Cl, An-N, An-O) were analyzed.
- Actinide-oxygen bonds showed significant covalent character, especially for elements heavier than thorium.
- Actinide-nitrogen and actinide-chlorine bonds exhibited predominantly ionic behavior.
- Quantum chemical calculations corroborated the experimental bonding analyses.
- Minor electronic or steric effects were observed for Pyx substituents.
Conclusions:
- The bonding in early actinide complexes is a mix of ionic and covalent interactions.
- The An-O bond exhibits a higher degree of covalency compared to An-N and An-Cl bonds.
- Pyridyl substituents have minimal impact on the overall complex properties.
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