Photoactivation of ruthenium phosphite complexes for olefin metathesis

The use of light to trigger olefin metathesis carries great potential for academic research and industrial applications. ^[1] For example, the design and synthesis of metathesis based polymeric materials by initiating the reaction with spatial and temporal control is a key feature in 3D printing and stereolithography. The commercially available olefin metathesis catalyst cis-Caz-1 is extremely robust, especially when reactions are carried out under air. This phosphite containing ruthenium complex only shows olefin metathesis activity at high temperatures. here, we report the photoactivation of cis-Caz-1 at room temperature with UVA light. Thus, a wide variety of olefin metathesis reactions was carried out at mild conditions with excellent yields. ^[2] Additionally, we discovered an interesting solvent effect in the photoinduced ring opening metathesis polymerization (ROMP) of 1,5 cyclooctadiene (COD). When the reaction is carried out in toluene a preferentially E-configuration of the double bonds in polyCOD is obtained. However, when the solvent is replaced by dichloromethane the selectivity is switched to a preferentially Z double bond polyCOD. Moreover, in order to investigate additional photoswitchable ruthenium phosphite complexes, we report the synthesis, characterization and catalytic activity of a novel phosphite-chelated ruthenium benzylidene complex, cis-PhosRu-1, which can be efficiently activated either by irradiation with 405 nm visible light or by heat.

[1] Eivgi, O.; Lemcoff N.G., Synthesis, 2018, 50, 49-63

[2] Eivgi, O.; Guidone, S.; Frenklah, A.; Kozuch, S.; Lemcoff, N.G., ACS catal., 2018, 8,6413-6418