Inherent Chirality and Stereoisomerism in Metallocorrole Sandwich Compounds

Abstract

In this thesis, I have presented my findings on stereoisomerism in eight-coordinate metallobiscorrole sandwich compounds. Metallobiscorroles were first synthesized in our laboratory about eight years ago and, although they were fully structurally characterized with X-ray crystallography, their crowded 1H NMR spectra essentially defied assignment. My master’s thesis project began with the task to synthesize partially fluorinated metallobiscorrole systems that would prove amenable to a full 1H and 19F NMR analysis. <p>

<p>Earlier density functional theory calculations on the metallobiscorroles indicated the possibility of two square-antiprismatic diastereomers in which the corroles are rotated approximately 45 and 135 degrees relative to each other. Furthermore, each diastereomer is inherently chiral, approximately C2-symmetric, and exists as a pair of enantiomers. The calculations also unambiguously indicated that each stereoisomer was configurationally stable, making the metallobiscorrole core doubly stereogenic, giving rise to both diastereomerism and enantiomerism. To date, however, only the 135 degree diastereomer has been experimentally reported. In this thesis, I have provided fully assignable NMR analysis of a handful metallobiscorrole complexes, and strong experimental evidence for the successful synthesis of both diastereomers and thereby formal proof of the doubly stereogenic character of metallobiscorrole sandwich complexes.