Ionic Grubbs–Hoveyda Complexes for Biphasic Ring‐Opening Metathesis Polymerization in Ionic Liquids: Access to Low Metal Content Polymers

Abstract

A novel ionic metathesis catalyst, [Ru(1‐CH3‐4‐CO2Py+)2(IMesH2)(CH‐2‐{2‐PrO}‐5‐NO2C6H3)][OTf−]2 (3 b; IMesH2=1,3‐dimesitylimidazolin‐2‐ylidene, Py=pyridine), has been prepared. 3 b and the Grubbs–Hoveyda catalysts [Ru(1‐CH3‐4‐CO2Py+)2(IMesH2)(CH‐2‐{2‐PrO}C6H4)][OTf−]2 (3 a) and [RuCl(1‐CH3‐4‐CO2Py+)(IMesH2)(CH‐2‐{2‐PrO}C6H4)][OTf−] (5 a) were used for ring‐opening metathesis polymerization (ROMP) reactions under both homogeneous and biphasic liquid–liquid conditions by using the ionic liquid 1‐butyl‐2,3‐dimethylimidazolium tetrafluoroborate ([BDMIM+][BF4−]) and toluene. All catalysts were active in the ROMP of norborn‐2‐ene‐based monomers, with cis‐cyclooctene and dicyclopentadiene providing good yields under homogeneous conditions and complex 5 a the most active catalyst. With all catalysts, the use of a chain transfer agent (CTA) allowed for the synthesis of polymers with low metal contents between 10 and 80 ppm, corresponding to a ruthenium removal of 98–99.8 % without any additional purification step. In addition, the use of a CTA allowed for recycling experiments under biphasic conditions, in which 3 a and 5 a were particularly active for several cycles.

Recent Advances Utilized in the Recycling of Homogeneous Catalysis

“…Ferraz et al . demonstrated the synthesis of nitro‐substituted ionic metathesis catalyst (Figure ) for biphasic ring‐opening metathesis polymerization (ROMP) in IL 1‐butyl‐2,3 dimethylimidazolium tetrafluoroborate([BDMIM + ][BF4 − ]) and toluene furnishing the synthesis of norborn‐2‐ene (NBE) based polymers in high yields . However, nitro‐substituted Grubbs‐Hoveyda complexes were less stable as compared to other catalysts.…”

High‐Performance Isocyanide Scavengers for Use in Low‐Waste Purification of Olefin Metathesis Products

“…Self‐scavenging catalysts contain a structural element that allows the efficient removal of both the catalyst and its residues from the postreaction mixture through extraction, adsorption, nanofiltration, or thermomorphic separation . However, the syntheses of such catalysts are often quite involved and, as a result, few of them are commercially available.…”

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

“…Ionic metathesis catalysts offer access to metathesis reactions in either aqueous solution [ 1 – 10 ] or under biphasic conditions [ 11 – 14 ]. Particularly the latter aspect is of utmost relevance in case of ionic liquids (ILs) can be used as the phase in which the catalyst is dissolved.…”

“…We recently reported on different Ru-based ionic metathesis catalysts that can be used for these purposes. In these systems, the charge is either located directly at the ruthenium [ 11 – 12 ] or at the 1-methylpyridinium-4-carboxylate ligands that are introduced via anion metathesis [ 13 – 14 ]. These novel catalytic systems have successfully been used under SILP conditions [ 11 , 15 ].…”