A phase-separable second-generation hoveyda-grubbs catalyst for ring-opening metathesis polymerization
Article first published online: 21 SEP 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Polymer Science Part A: Polymer Chemistry
Volume 50, Issue 24, pages 5211–5212, 15 December 2012
How to Cite
- Issue published online: 14 NOV 2012
- Article first published online: 21 SEP 2012
- Manuscript Received: 17 AUG 2012
- Manuscript Accepted: 17 AUG 2012
Vol. 50, Issue 19, 3954–3959, Article first published online: 21 JUN 2012
The authors of this article have notified us of errors in the article. The corrected information is shown below. We apologize for any inconvenience this may have caused.
ABSTRACT: Polyisobutylene-supported second-generation Hoveyda-Grubbs catalyst is shown to be an effective nonpolar phase tag for ring-opening metathesis polymerization (ROMP). The catalytic activities of the supported Ru–carbene complex in ROMP are comparable to those of their homogeneous counter- parts. The separability of these catalysts leads to lower Ru contamination in the polymer products in comparison to the nonsupported Hoveyda-Grubbs catalyst. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
KEYWORDS: metathesis; phase separation; polyisobutylene-supported N-heterocyclic carbene; ROMP; second-generation Hoveyda-Grubbs catalyst.
Inductively coupled plasma mass spectrometry (ICP-MS) analysis was used to determine the content of Ru leaching in the polymer products. The results are listed in Table 1. In these experiments, a portion of the solid polymer product was digested to form a solution of Ru in nitric acid. In that process, the Ru content of that solid sample was diluted to form nitric acid solutions that had Ru contents of 0.4 – 0.6 ppm when products formed by polymerizations using the PIB-bound Ru catalyst were analyzed. These ppm values varied depending on the amount of sample digested and the volume of the nitric acid. A similar analysis of a polymerization product isolated from hexane/dichloromethane polymerization using a low molecular weight Grubbs-Hoveyda complex yielded a nitric acid solution with 10.1 ppm Ru. Using these concentrations of Ru in the analysis solutions, the concentration of the Ru in the solid polymers could be calculated: polymer 15 (entry 1), 127 ppm of Ru; polymer 16 (entry 2), 111 ppm of Ru; polymer 17 (entry 3), 167 ppm of Ru; and polymer 18 (entry 4), 228 ppm of Ru. All of the polymerization products formed using the PIB-supported complex had much lower Ru leaching and lower Ru concentrations in the polymer products than a polymer formed using a low molecular weight Grubbs-Hoveyda complex.
To further establish that the low Ru contamination of the product was due to the use of a soluble polymer-bound Ru catalyst and to show that the use of PIB ligands did not significantly affect the polymerization reaction, we carried out ROMP polymerizations analogous to those in Table 1 using the analogous low-molecular-weight Ru complex 3. A ROMP reaction was carried out with monomer 13 using complex 3 under the conditions listed in Table 1. The reaction mixture was worked up using a procedure identical to that used in a ROMP of monomer 13 with complex 9. After solvent precipitation, the product homopolymer 17 obtained was highly colored as shown in Figure 2. ICP-MS analysis of this solid polymer showed that it contained 73% of the starting Ru (4764 ppm Ru) (Table 1, entry 5). This is in contrast to the white polymer product formed using complex 9, which contained 3.3% of the starting Ru (167 ppm Ru) (Fig. 2).