Abstract
This thesis describes investigative synthetic and structural studies on the chemistry of the [nido-7,8-C2B9H11]2- ligand. The chemistry of group XII, XIII, IV and V metallacarborane complexes derived from this dicarbollide dianion was explored.Chapter 1 provides an introduction to the field carborane cluster compounds and describes the structure, bonding and preparation of these compounds with discussion on the electronic and structural features of these species. Metallacarborane chemistry is also discussed with reference to literature examples. Aspects of metal-ligand bonding that are pertinent to the work presented in this thesis are also outlined.
Chapter 2 investigates the synthesis of metallacarborane complexes of zinc which are currently vastly underexplored. Thus far there are only three zinc dicarbollide complexes featuring a Zn2+ metal centre reported in the literature. This chapter describes the preparation and characterisation of a series of zinc dicarbollide species which utilises a combination of the dicarbollide ligand and a strong σ-donating N-heterocyclic carbene to stabilise the Zn2+ metal centre. Herein the first η5 coordinated zincacarborane complexes are reported and structurally characterised. The effect of changing the steric demand of the N-substituents of the carbene is also examined.
Chapter 3 probes the chemistry of main group dicarbollide complexes. It focuses on and expands upon the chemistry of Group XIII metallacarboranes, an area that is also relatively under-investigated compared to other main group elements. This chapter discusses the preparation and reactivity of derivatives of the alkyl aluminacarborane [{η5-C2B9H11}AlMe], which is currently only prepared in very low yield under extremely harsh conditions. The Lewis-acid behaviour of these species and the synthesis of gallium and indium analogues is also explored.
Chapter 4 explores the early transition metal dicarbollide chemistry of Group IV metals titanium and zirconium, which is less established than that of the mid to late transition metals. Reaction of 7,8-C2B9H13 with the homoleptic metal amide M(NMe2)4 (M = Ti, Zr) affords the half-sandwich complex [{η5-C2B9H11}M(NMe2)2(NHMe2)] (M = Ti, Zr). These mono-dicarbollide derivatives were investigated for their reactivity in ligand substitution reactions with protic acids and Lewis bases.
Chapter 5 expands upon the investigation into early metal dicarbollide chemistry, with a focus on the preparation and reactivity of tantallacarborane half-sandwich complexes derived from the tris-amide species [{η5-C2B9H11}Ta(NMe2)3]. This chapter also discusses the synthesis and characterisation of mixed dicarbollide/imido complexes of tantalum.
Chapter 6 provides full details of the synthetic experimental procedures conducted and the characterisation of the novel compounds discussed in this thesis by microanalysis, NMR spectroscopy and single-crystal X-ray diffraction.
| Date of Award | 29 Mar 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Andrew Johnson (Supervisor) & David Liptrot (Supervisor) |
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