Master of Science
Blacquiere, Johanna M.
Complexes of the type [M(Cp/Cp*)(MeCN)(PR2NR′2)]PF6 (M = Fe, Ru) were synthesized and/or tested towards acceptorless dehydrogenation (AD) of amines. The primary amine benzylamine can undergo AD to form a mixture of products, and a selection of catalysts were employed in an attempt to control product selectivity. As a result, trends in product distribution were observed by modifying the primary and secondary coordination spheres on the catalyst. A new complex, [Fe(Cp)(MeCN)(PPh2NPh2)]PF6 (3a) was synthesized and characterized and was found to be a completely selective dehydrogenation catalyst. This is the first example of an iron catalyst capable of selective dehydrogenation without the need for an exogenous base. Mechanistic analysis was conducted using in-situ IR spectroscopy to elucidate the reaction rate order, and rate-determining step for [Ru(Cp)(MeCN)(PPh2NPh2)]PF6 (1a) using indoline. The results of these mechanistic studies suggest that the catalytic mechanism for 1a is a cooperative outer sphere mechanism.
Summary for Lay Audience
A catalyst is a substance that helps make chemical reactions easier. The chemical reaction focused on in this Thesis removes H2 from molecules and releases it as hydrogen gas. However, there is more than one possible product, and there are many factors that determine the amounts of each product formed. To understand why a particular product is favoured over another, multiple different catalysts were tested. A new catalyst was made and is like a previously known catalyst. The new catalyst has iron in its structure, instead of the previously known catalyst, which had ruthenium. The iron catalyst was the most selective out of all the catalysts tested and is one of the first examples of an iron catalyst capable of doing this reaction. Studies to understand more about how these catalysts work were conducted, and the tested catalysts react differently compared to other known catalysts used for H2 removal. The reason why they act differently is because of the way the structure around the metal was designed. This structure can be fine-tuned to make a chemical reaction more efficient. Using iron as a cheap alternative to precious metals like ruthenium, and further modification of the iron catalyst, could result in cheaper, more effective catalyst with a variety of different applications. Some applications include using a catalyst to store and release hydrogen as a potential fuel source, as well as employing catalysts for more eco-friendly synthesis of pharmaceuticals.
Hoffman, Matthew D., "Metal Ligand Cooperative Complexes for Acceptorless Dehydrogenation of Amines" (2021). Electronic Thesis and Dissertation Repository. 8306.
Available for download on Friday, December 01, 2023