Coordination and reactivity of main group multiple bonds

• Main Author: Townsend, Nell S.
• Published: University of Bristol 2013
• Subjects: 541.2242
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627963

The work presented in this thesis encompasses two research areas; phosphaalkyne chemistry and gold(I) coordination complexes. In parts, the two topics overlap. Chapter 2 focuses on the synthesis, manipulation and coordination of phosphaalkyne substrates. A variety of phosphaalkynes are synthesised, but the majority of the work presented deals with the kinetically stabilised PCtBu. A modified synthesis of PCtBu is reported utilising an improved apparatus set up, allowing for safer preparation of large quantities of PCtBu. The synthesis of the unstable phosphaalkyne PCH is also reported along with attempts to obtain the first coordination complex. Investigation into the interaction between gold and tantalum metal centres with phosphaalkyne substrates has led to characterisation of the first gold(I)-phosphaalkyne complex and a series of tantalum-phosphaalkyne cations. The formation of main group frameworks is achieved from the thermal coupling of phosphaalkynes with pnictogen trihalides. This leads to a variety of P/Clhalogen cages and incorporation of arsenic was achieved resulting in a novel P/CIAs framework. In addition a unique spiro-PsC6 compound was crystallographically observed. Chapters 3 and 4 focus on the coordination chemistry of a trimer of PCtBu, 2,4,6- tritert-butyl-I,3 ,5-triphosphabenzene. The first crystallographically characterised examples of an r{triphosphabenzene are obtained along with a theoretical investigation into the aromaticity of the complexes. Reactivity towards pnictenium ions is also explored both computationally and experimentally. Unprecedented main group architectures are obtained when arsenic is incorporated into the framework, whereas phosphenium ions form novel 1,4-addition products. Chapters 5-6 move away I from phosphorus-carbon triple bonds and address the interaction of gold(I) cations with carbon-nitrogen multiple bonds. The gold(I) cations utilised in the previous chapters are applied towards complexation of Nheterocycles and azides. The work reports 11 novel complexes of a range of nitrogen containing substrates, from the simple pyridine and azide to nitrogen rich L Abstract heterocycles 2,4,6-triphenyl-l,3,5-triazine and hexachlorocyclotriphosphazene. An unusua~ bonding interaction is observed in bipyridine complexes where symmetric vs. asymmetric K2 complexation is dictated by the gold(I) ligand. The work in this thesis has resulted in several publications outlined below: Chapter 2 Townsend, N. S.; Russell, C. A, Phosphorus(III) Ligands in Homogeneous Catalysis: Design and Synthesis, First Ed. Chapter 11 Phosphaalkynes. John Wiley & Sons Ltd, Published 2012 . . Sanguramath, R. A; Townsend, N. S.; Lynam, 1. M., Russell, C. A, Eur. J Inorg. Chem., 2013, asap. Doi: 10.l002/ejic.201301089. Chapter 3 Townsend, N. S.; Green, M.; Russell, C. A, Organometallics, 2012, 31,2543. Chapter 4 Townsend, N. S.; Shadbolt, S. R.; Green, M.; Russell, C. A, Angew. Chem. Int. Ed., 2013, 52, 3481. ;' 11