Nuclearity, structure and properties of tiara-like complexes

• Autores: Harry J. Martin
• Directores de la Tesis: Neil Champness (dir. tes.), María del Carmen Giménez López (dir. tes.)
• Lectura: En la University of Nottingham ( Reino Unido ) en 2018
• Idioma: inglés
• Enlaces
  • Tesis en acceso abierto en: eprints.nottingham.ac.uk
• Resumen

  • The work in this thesis principally describes the synthesis and formation of a series of tiara- like complexes, a class of cyclic transition metal complexes of varying sizes. Despite the numerous examples of this class of complex within the scientific literature, little to no control over the size of the reported molecules is reported. This work aims to attain some degree of selectivity over the nuclearity of the synthesised complexes by two methods; firstly, the modification of reaction conditions with a focus on the choice of solvent used for the synthesis and the second method involving a modification of the structure of the ligand used.

    Five tiara-like complexes have been synthesised and characterised. The first of these, Pd NAC (1), gives only a single, six-membered product when the reaction is performed using THF as the solvent. When protic alcohols are used instead of THF, additional complexes of different sizes are seen within the MALDI mass spectrum. Replacement of the amide group of the ligand with an ester to remove the possibility of hydrogen-bonding shows the synthesis of six- membered and eight-membered rings when the complex is synthesised in THF. Electrolysis of a DMF solution of 1 results in accumulation of charge accompanied by a change of colour from yellow to red-brown; TEM imaging of the solution shows the presence of Pd nanoparticles.

    The second tiara synthesised, Pd ETG (2), gives a larger eight-membered ring which results from the relocation of the carbonyl moiety relative to 1. This complex was shown to be able to host two molecules of methyl iodide, as evidenced by the single crystal structure; this is the first and only example of a tiara-like complex able to encapsulate two molecules of solvent simultaneously.

    The same ligand, methyl 3-mercaptopropionate (MMP) was used to synthesise both nickel- and palladium-containing tiara-like complexes. The two isomers are compared in detail by NMR and crystallography; the palladium complex crystallises into a higher symmetry R-3 space group when compared to P-1 for the nickel complex. Mixed Pd/Pt tiara-like complexes were examined; it was observed that modification of the starting ratio of the metal precursors gave a corresponding shift in the ratio of the mixed products observed in the mass spectra.