A synthetic and structural investigation of pnictogen and chalcogen peri-substituted naphthalenes

Abstract

Donor–acceptor complexes have been known for over a century and enjoy a long list of applications in chemistry. The work presented in this thesis explores the dative interaction between phosphorus and its heavier congener bismuth. Utilising peri-substitution, atoms can be forced in close proximity to one another resulting in a repulsive (non-bonding) interaction or an attractive (bonding) interaction. Hence, peri-substitution can be used to support traditionally ephemeral species. A range of phosphorus and bismuth containing peri-substituted compounds were synthesised and characterised using multi-nuclear NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction with the data for several structures collected and solved personally. Where the bismuth moiety contained two aryl groups, no bonding interaction between the phosphorus and bismuth was observed owing to the poor Lewis acidity of the bismuth. Upon increasing the Lewis acidity, by exchanging one of the aryl groups with a halogen, the formation of a donor‒acceptor complex was observed. This series of compounds represents rare examples of structurally characterised phosphine‒bismuthine donor‒acceptor complexes. The formation of bismuth(V) derivatives proved to be incredibly challenging with only one compound obtained. The compound was identified as a phosphino‒bismuthonium salt. The coordination of S,S bidentate ligands remains an important area of chemistry. Complexes bearing this type of ligand have a number of industrial applications including catalysts in vulcanisation and lubricant additives. These complexes can also show a range of electrochemical properties and can support unusual magnetic properties. Two series of rhodium and iridium complexes were prepared using aromatic dithiolates of varying flexibility and size. These were characterised using multinuclear NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction with the data for most of the structures collected and solved personally. Bimetallic complexes were shown to form via bridging sulfur and/or chlorine atoms when the metal centre was coordinatively unsaturated. A large variation in the type of structure was observed depending on the flexibility of the aromatic backbone with an interesting tetrameric structure obtained when the biphenyl backbone was utilised. Monomeric forms of the complexes were obtained using a phosphorus donor to occupy the vacant site. The change in flexibility of the backbone was shown to have little effect on the structure formed. Altering the size and electronics of the phosphorus ligand was investigated with the electronic properties shown to overcome any steric restrictions imposed by an increased size as determined by the Tolman cone angle.