Dioxygen insertion studies into platinum and palladium alkyl complexes

• Main Author: Petersen, Allan Robertson
• Other Authors: Britovsek, George
• Published: Imperial College London 2012
• Subjects: 546.645
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555951

Chapter 1 provides an overview of the oxidation of methane by platinum salts known as Shilov chemistry. This includes platinum complexes used for the selective oxidation of methane to methyl bisulfate. Attention is paid to model platinum complexes that have been synthesised to explore the oxidation of methane using dioxygen as the oxidant. Chapter 2 describes two sets of tridentate N donor ligands that have been synthesised. The first set contains 6,6ʹʹ-disubstituted-2,2ʹ:6ʹ,2ʹʹ-terpyridine ligands, of these two new ligands 6,6ʹʹ-di(methylamino)-2,2ʹ:6ʹ,2ʹʹ-terpyridine and 6,6ʹʹ-dimethoxy-2,2ʹ:6ʹ,2ʹʹ-terpyridine have been synthesised and fully characterised. The second set contains non-terpyridine tridentate ligands. The synthesis and characterisation of novel cationic platinum(II) methyl complexes bearing these ligands is described in Chapter 3. The structures of some of these complexes have been determined by X-ray crystallography. Further, the reactivity of the complexes towards dioxygen is reported and how different reactivity is imparted by the different ligands is discussed. The ability of some of these platinum(II) methyl complexes to insert dioxygen into their M-Me bonds arises from the steric interaction between the Pt-Me ligand and the substituents in the 6- and 6ʹʹ-positions on the terpyridine ligand. Chapter 4 describes a study into the mechanism of the insertion of dioxygen into a Pt-Me bond. This includes deuterium labelling experiments, which led to the discovery of the exchange of methyl ligands between platinum(II) and palladium(II) centres. A mechanism for this exchange involving the formation of a MII-MII dimer is proposed. In addition, the decomposition of a palladium(II) methylperoxo complex to give an intriguing new metallacyclic hemiacetal alkoxide complex is described. A possible mechanism for the formation of this new palladium(II) complex is discussed. The synthesis and characterisation of the new compounds discussed in Chapters 2-4 are reported in Chapter 5.