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Title: Metal-metal bonding in poly-metallic systems
Author: Al-Nafee, Mohammed
ISNI:       0000 0004 8503 5201
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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This thesis focuses on the nature of metal-metal bonding in poly-metallic systems. The electronic structures of examples of this class are studied using both density functional theory (DFT), time-dependent density functional theory (TD-DFT), periodic density functional theory and also the complete active space self-consistent-field (CASSCF) methodology. The thesis starts with a broad introduction to the chemistry of metal-metal bonded systems in chapter 1, where the focus is on the historical development of our understanding of the metal-metal bond from both experimental and theoretical perspectives. Potential applications of metal-metal bonded species are also covered. In chapter 2, a brief introduction of theoretical techniques used in this thesis is presented, covering Hartree-Fock theory, multi-configurational approaches and density functional theory, along with a discussion of basis sets. The first of the main results chapters, chapter 3, covers the electronic structure of face-shared trimetallic systems, [(PEt3)3Ru(MCl6)Ru(PEt3)3]z+, where M= Ru, Rh and Ir. Our aim here is to provide a framework for interpreting the available structural and spectroscopic evidence, and use this insight to establish how metal-metal interactions change as a function of the identity of the metal ions and also their oxidation states. Our results suggest that the switch from Ru to Rh/Ir in the central position induces a marked shift from a delocalized regime to one where unpaired electrons on the outer Ru centers only interact weakly via super exchange. The nature of the metal-metal bonding of face-shared tetra-metallic systems, [(PEt3)3Ru(Ru2Cl9)Ru(PEt3)3]1+, is the subject of chapter 4. Here we make the comparison with 'naked' [Ru2Cl9]3-, and show that whilst reduction processes are localized on the Ru2Cl9 core, oxidation takes place at the external Ru centres, leading to metal-metal bonding that extends across the entire Ru4 chain. In Chapter 5, the electronic structure of (Cp*RuCl)2(mu - Cl)2 system is discussed. This system is unique in so much as two molecules with very different Ru-Ru bond lengths co-exist in the solid-state. We have used periodic density functional theory to confirm that the crystallographic state is indeed the lowest energy one, but that relatively minor perturbations to the environment can drive transition to states where both Ru-Ru bonds are either long or short.
Supervisor: McGrady, John E. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Metal-Metal Bonds in Transition Metal Systems