New routes to chiral-at-metal organometallic complexes and their application in asymmetric synthesis

Shroot, Stephanie

Abstract

This project develops new organometallic frameworks, to target the asymmetric transfer hydrogenation and hydrosilylation of ketones, aiming for enhanced activity and substrate scope relative to current state-of-the-art. The anticancer activity of some of the complexes were assessed against a human colorectal adenocarcinoma cell line. The first chapter of this work discusses relevant research published, identifying key areas that possess limitations.
Chapter 2 describes the synthesis of tethered ruthenium(II) half-sandwich complexes, constructing structures bearing chirality within the tether; a prospect not yet explored. The key to this design is the stereocentre, situated at the benzylic position. A bulky substituent, methyl, isopropyl or t-butyl, emanates hoping to control the tether coordination. The tether was designed to influence the metal-centred configuration and thus the configuration of the ATH product. Although configurational exchange was seen over time, the complexes yielded
products in modest ee.
Chapter 3 describes the synthesis of manganese(I) half-sandwich frameworks, aiming to incorporate a stereocentre into the tether so the approach of the substrate to the complex during hydrosilylation would be influenced by the steric bulk of the tether. Irradiation of the achiral tethered complexes outlined in this chapter showed great promise, hence if the reaction conditions can be tuned accordingly, the frameworks can still be considered as good target complexes to be used in hydrosilylation.
Chapter 4 describes exploration towards the synthesis of a polymer-supported ruthenium(II) half-sandwich complex, analogous to those developed in Chapter 2, anticipated to be capable of the asymmetric transfer hydrogenation of ketones. Frameworks in the literature incorporate supports through amino, sulfonamide or phenyl groups within the ligand, allowing for cheaper and less toxic reaction conditions, and advantageous recyclability, without loss of enantioselectivity. The anticipated immobilisation during this project was via the stereocentre on the tether, but due to time limitations immobilisation was not performed.

Citation

Shroot, S. New routes to chiral-at-metal organometallic complexes and their application in asymmetric synthesis. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4224096

• Thesis Type: Thesis
• Deposit Date: Mar 31, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4224096
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Dec 1, 2021