Synthesis and reactivity of gold(III) complexes with pincer ligands

• Main Author: Rosca, Dragos-Adrian
• Published: University of East Anglia 2014
• Subjects: 540
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614589

This thesis explores the synthesis, characterisation and reactivity of catalytically relevant gold(III) species supported by pincer ligands. The tridentate diphenylpyridine ligand was found to stabilise monomeric, terminal hydroxides of gold(III) which are reactive synthons for new metal complexes. Chapter 1 explores the chemistry of terminal gold(III) hydroxides and their usefulness in the synthesis of photoluminescent materials. In Chapter 2 we show that pincer-supported terminal gold(III) hydroxides can also be used in combination with a hydride source to access gold(III) hydride complexes, a fundamentally important complex type which has until now eluded isolation and characterisation. We show that gold(III) hydrides can also be readily reduced to give dimeric, gold(II) complexes with an unsupported Au-Au bond, which possess unprecedented thermal stability. A comparison with the one electron reduction of gold(I) hydrides is also presented. Gold(III) hydroxides are useful synthons for preparation of gold(III) peroxide complexes,another class of gold complexes which are hitherto unexplored. Chapter 3 presents the first data on the characterisation and chemistry of these species. While studying their reactivity, we found that gold(III) peroxides can be converted into gold(III) hydrides via successive phosphine mediated oxygen transfer reactions. Since this type of reactivity was not known for any other metal, kinetic investigations are presented. We show that in contrast to gold(III) hydrides, NHC supported gold(I) hydrides undergo the reverse reaction, namely oxygen insertion into the Au—H bond, giving rise to gold(I) peroxides. In the last chapter of this work, Chapter 4, we show that tridentate pincer ligands can stablise gold(III) cations in the presence of olefin complexes. We present for the first time strong NMR evidence of the existence of gold(III) olefin complexes and reactivity studies towards nucleophiles. Chapter 4 also describes the synthesis of gold(III) azides and our attempts to use highly fluorinated β-diketiminate ligands in gold(III) chemistry.