Multimetallic Azole and Carbene Complexes in Supramolecular Chemistry and Catalysis

The development of tritopic azole ligands tethered to the cyclotriveratrylene (CTV) molecular host is described within this thesis. The assembly of tripodal pyridyl-CTV ligands with metal precursors has led to the discovery of a diverse range of metallo-supramolecular assemblies, but comparable ligands incorporating five-membered ring counterparts are considerably less developed. New azole ligands could potentially coordinate to metals at different bite angles compared to the established pyridyl systems, leading to the assembly of previously inaccessible architectures. Furthermore, azoles, in particular 1,3-diazoles, are precursors to organometallic N-heterocyclic carbene (NHC) complexes. The fusion of NHC ligands and CTV cavitands has not previously been investigated.
A tritopic benzimidazole ligand was prepared, which assembles with [Pd(Cl)2(MeCN)2] to yield a rare trans-linked metallocryptophane as an alternative to the more commonly encountered architectures requiring a cis-protected Pd(II) precursor. Additionally, the coordination of an oxazole ligand was investigated, leading to the assembly of 1D polymer chains.
The assembly of a 4-thiazolyl ligand with AgBF4 and AgReO4 led to the assembly of the first CTV-type coordination cubes, with chiral self sorting upon coordination to Ag(I) and spontaneous resolution of crystals being exhibited. In addition to cubic cages, 2D and 3D coordination polymers were also accessible upon coordination to Ag(I).
The first metal-NHC complexes on a CTV scaffold were also prepared, with Ir(III) and Ru(II) complexes being examined as catalysts in the transfer hydrogenation of acetophenone, suggesting that in the case of Ru(II), intermolecular cooperativity may be exhibited.
Trinuclear Pd(II)-NHC complexes were targeted, and examined as catalysts in the regioselective Suzuki-Miyaura reaction of 2,4-dibromopyridine and 4-methoxybenzeneboronic acid. Catalysts displayed high activities over a short period of time, preparing traces of the ‘favoured’ o-coupled product and significant quantities of para- and bis-coupled products, potentially via two pathways.