{"id":26812,"date":"2024-02-19T17:05:05","date_gmt":"2024-02-19T17:05:05","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=26812"},"modified":"2024-02-19T17:05:05","modified_gmt":"2024-02-19T17:05:05","slug":"mechanistic-templates-computed-for-the-grubbs-alkene-metathesis-reaction","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=26812","title":{"rendered":"Mechanistic templates computed for the Grubbs alkene-metathesis reaction."},"content":{"rendered":"
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Following on from my template exploration of the Wilkinson hydrogenation catalyst, I now repeat this for the Grubbs variant of the Alkene metathesis<\/a> reaction. As with the Wilkinson, here I focus on the stereochemistry of the mechanism as first suggested by Chauvin[1]<\/a><\/span>, an aspect lacking in eg the Wikipedia entry. As before, the diagram below is hyperlinked to the appropriate data repository identifier so that you can go straight from the scheme to the data (Top level Data DOI: 10.14469\/hpc\/13796<\/a>).<\/p>\n

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The essence of the reaction is the formation of a metallacyclobutane intermediate, which being approximately symmetrical with a plane of symmetry, can revert to the catalyst and an alkene in one of two ways, reforming the original alkene (two red dot carbons) or a forming a methathesised alkene (red-blue dot carbons).<\/p>\n

Although the mechanism is often described as a [2+2] cycloaddition in which d-orbital participation from the metal lowers the activation energy significantly, calculations at the MN15L\/Def2-TZVPPD\/SCRF level\u00a0indicate there can be up to four discrete steps involved in the process. There are three routes involving these steps that the calculations (B3LYP+GD3+BJ\/Def2-TZVPPD\/SCRF=DCM) reveal (DataDOI 10.14469\/hpc\/13796<\/a>). The starting point for all three routes is the most stable reactant catalyst (left above) which has the H-C-H carbene group in the same plane as the P-Ru-P atoms.<\/p>\n

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  1. The red route<\/strong> involves the following steps:\n