Electronic Structure and Bonding in Molecular f Element Chemistry

Abstract

This thesis focuses on the electronic structure of uranium in molecules, and in particular uranium-nitrogen chemistry. Theoretical techniques, most notably density functional theory (DFT) and multiconfigurational calculations, are used to analyse novel bonding. Multiconfigurational calculations are performed on the molecules EUF3 (E = N-Bi) in Chapter 3. NUF3 is identified as having a triple U-N bond, but PUF3 and AsUF3 are identified as having single bonds, in contrast to previous studies which used a smaller active space and identified a triple bond for all three molecules. A U(V)-N2 complex is studied in Chapter 4, a rare example of a high oxidation state metal centre binding to a poor pi donor ligand. Potential energy surface calculations scans demonstrate that the U-N2 potential is shallow, and while DFT under-predicts the U-N2 bond length, post-Hartree Fock calculations on a model system are closer to the crystal structure. Diuranium complexes which feature a diamond U2X2 motif are studied in Chapters 5, 6 and 7. In Chapter 5, the synthesis of a U(IV) U2N2 complex is reported, alongside a study of its electronic structure where a 12 electron delocalised bonding system is identified. Chapter 6 builds on this work, comparing the U(IV) complex studied in Chapter 5 with the two other previously reported U2N2 ring-containing complexes. Complexes U2X2 rings with different bridging ligands are studied in Chapter 7. The relationship between bonding in the ring and magnetic properties is explored. Chapter 8 reports the isolation, characterisation and computational study of the ditungsten decacarbonyl dianion. The crystal structure obtained has the carbonyl complex in the eclipsed conformer. Calculations are performed on the gas phase dianion which predict the staggered geometry is preferred, suggesting that the observed geometry is due to crystal packing forces.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Nikolas Kaltsoyannis (Supervisor) & Nicholas Chilton (Supervisor)