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 introduction of phosphite ligands to Grubbs type complexes resulted in stable slow initiating complexes. Phosphite additives were used by Moore and co-workers to modulate the frontal ring opening metathesis polymerization of dicyclopentadiene,^[2] while phosphite containing ruthenium indenylidene complexes reported by Cazin et al. are extremely robust, especially when olefin metathesis reactions were carried out under air.^[3] Although highly efficient, these catalysts could only promote olefin metathesis reactions at elevated temperatures. Here, we report the photoinduced activation of commercially available phosphite complex cis-Caz-1 at room temperature with UVA light. Thus, a wide variety of olefin metathesis reactions were carried out under ambient conditions with excellent yields.^[4] To further study the activity of phosphite complexes for photoinduced olefin metathesis, we report the synthesis charachterization and catalytic activity of three new benzylidene phosphite complexes.^[4-5] A chelated benzylidene cis-PhosRu-1, and two non-chelated complexes cis-Ru-1 and cis-Ru-2. These new complexes are latent towards olefin metathesis at ambient temperatures, and can be switched on by irradiation of visible light to produce excellent catalytic activity. Complex cis-Ru-1was found suitable for 3D printing applications, while complex cis-Ru-2 was designed with a chromatic orthogonal self-destruction switch allowing the destruction of the catalyst with shortwave UV light.

[1] Eivgi, O. et al. Synthesis, 2018, 50, 49-63.

[2] I. D. Robertson et al. Nature 2018, 557, 223-227.

[3] (a) S. Guidone et al. ACS Catalysis 2015, 5, 2697-2701; (b) X. Bantreil et al. Chem. Commun. 2010, 46, 7115-7117.

[4] Eivgi, O. et al. ACS catal., 2018, 8,6413-6418

[5] Eivgi, O. et al. Unpublished