Nobel Chemistry in the Laboratory: Synthesis of a Ruthenium Catalyst for Ring-Closing Olefin Metathesis

Abstract

An experiment for the upper-level undergraduate laboratory is described in which students synthesize a ruthenium olefin metathesis catalyst, then use the catalyst to carry out the ring-closing metathesis of diethyl diallylmalonate. The olefin metathesis reaction was the subject of the 2005 Nobel Prize in chemistry. The catalyst chosen for this experiment is the ruthenium alkylidene complex that is most practical to synthesize in an undergraduate laboratory for reasons of time, safety, and cost of materials. The three-step synthesis of (PCy3)2Cl2Ru(=CH–CH=CMe2) from RuCl3·H2O goes through [(COD)RuCl2]x and Ru(H)(H2)(Cl)(PCy3)2 as intermediates. The latter complex is air sensitive, giving students the opportunity to learn Schlenk techniques. The ring-closed product is purified by column chromatography, and the catalyst and the ring-closed product are characterized by NMR spectroscopy.