Synthesis and reactivity of copper(I) and aluminium(III) complexes of N-heterocyclic carbenes

Abstract

N-heterocyclic carbene (NHC) ligands are nowadays an irreplaceable tool for the stabilisation of both transition metal (TM) and main group (MG) elements. NHC-TM complexes have been widely studied and successfully applied in catalysis, whereas NHCs have enabled the isolation and characterisation of elusive MG species, as for example with the MG element in a low oxidation state. In this thesis, investigation of both classes is covered, utilising copper(I) as TM and aluminium(III) as MG element. Regarding NHC-copper(I) species, the first investigation was their application as catalysts for the synthesis of 2-substituted oxazolines and 2-substituted thiazoline from nitriles and aminoalcohols or aminothiols respectively (Chapter 2).The second focus lies in the functionalisation of the copper centre by changing the anionic ligand to obtain new NHC-copper(I) complexes. Two different classes were synthesised, the first bears azole ligands (Chapter 3) and the second azide (Chapter 4). The former were applied in the hydrosilylation of ketones and mechanistic investigations were performed in order to ascertain the effect of both the NHC and azole ligand on catalytic activity. The latter was reacted with different organic molecules and with cationic NHC-copper(I) species to explore the reactivity of the azide moiety. Concerning NHC-aluminium(III) complexes, the main focus was the functionalisation of [AlH3(NHC)] species to obtain new compounds and study of their reactivity (Chapter 5). Different transformations, ranging from halogenation to the reaction with bis(pinacolato)diboron, are covered. Moreover, attempts to reduce Al(III) complexes to low valent aluminium species are presented.