A New Approach To Studying the Mechanism of Catalytic Reactions: An Investigation into the Photocatalytic Hydrogenation of Norbornadiene and Dimethylfumarate Using Polyethylene Matrices at Low Temperature and High Pressure

TLDR: In this paper, the combination of polyethylene (PE) matrices and high pressure−low temperature (HPLT) experiments can be used to provide new mechanistic information on hydrogenation processes.

Abstract: This paper presents a new method for investigating the mechanisms of homogeneously catalyzed reactions involving gases, particularly H2. We show how the combination of polyethylene (PE) matrices and high pressure−low temperature (HPLT) experiments can be used to provide new mechanistic information on hydrogenation processes. In particular, we show how we are able to generate reaction intermediates at low temperature, and then to extract the contents of the PE film at room temperature to characterize the organic products using GC-MS. We have used our new technique to probe both the hydrogenation of dimethyl fumarate (DF), using Fe(CO)4(η2-DF) as the catalytic species, and the hydrogenation of norbornadiene (NBD), using (NBD)M(CO)4 (M = Cr or Mo) as the catalytic species. Irradiation of Fe(CO)4(η2-DF) in a PE matrix at 150 K resulted in the formation of an intermediate complex tentatively assigned Fe(CO)3(η4-DF). Warming this complex to 260 K under H2 leads to the formation of Fe(CO)3(η2-DF)(η2-H2). Further...