Exploring the Coordination Potential of Monodentate and Bidentate Bicyclic Guanidine Ligands

Abstract

<p>This thesis reports investigations of the interaction of arene-bicyclic guanidine ligands, using the 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) guandine (Figure i) as a foundation, with a variety of metal centres. Beginning with 1-benzyl-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (Ph(CH2hpp)), attempts were made to coordinate this ligand to group 1 metal N{SiMe3}2- salts, which resulted in a novel NaN{SiMe3}2 crystal structure. Ligands comprised of a phenyl group with multiple hpp units in varying substitution patterns were also synthesised and reacted with group 1 metal N{SiMe3}2- salts to investigate the possibility of bidentate and tridentate arene-hpp coordination. This resulted in the synthesis of two novel compounds containing KN{SiMe3}2. Both sigma and pi-interactions with potassium were observed in the crystal structure of one of these compounds. NMR data that support analogous coordination to lithium and sodium analogues were also obtained. The ligands with multiple hpp units were introduced to highly reactive main group antinomy and bismuth species in an attempt to achieve a coordination with increased hapticity of the pi-interaction. A novel antimony structure was obtained with asymmetric coordination of an arene-hpp ligand in which an intramolecular C-H activation was achieved. An N-phosphino guaninde was synthesised and employed in this research due its potential to coordinate through both its available nitrogen and phosphorus atoms. This ligand was reacted with a variety of metal centres which revealed information about the strength of the N-P bond in the ligand. Two novel crystal structures were obtained which both contained novel group 1 clusters with coordinating hpp units. Finally, attempts were made to coordinate Ph(CH2hpp) to transition metal halides and N{SiMe3}2- salts. These attempts resulted in one novel crystal structure.</p>