Nature of the Propagating Species in Ring-Opening Metathesis Polymerizations of Oxygen-Containing Monomers Using Well-Defined Ruthenium Initiators

Abstract

The propagating alkylidene species that arise during the ring-opening metathesis polymerization (ROMP) of a range of strained bicyclic monomers initiated by RuCl2(PCy3)2(dCHPh) [1] and RuCl2(PCy3)(dCH-o-O-i-PrC6H4) [2] have been identified using 1 H NMR spectroscopy. For polymerizations initiated by 1 in which the monomers do not contain oxygen, a single set of two NMR signals are observed for the resting state of the propagating species. These correspond to bisphosphine-ruthenium complexes with the proximal backbone double bond either cis or trans. When the monomers contain oxygen, an additional set of two NMR signals are observed for the resting state of the propagating species. These correspond to monophosphine species which also have oxygen from the polymer backbone complexed to the ruthenium, again with the proximal backbone double bond either cis or trans. Resonances attributed to bisphosphine and monophosphine species have been conclusively assigned by the addition of CuCl or PCy 3. Assignments were further confirmed by the study of comparable ROMP reactions initiated by 2. Bisphosphine propagating species are not normally observed during ROMP reactions initiated by 2. If the monomer contains oxygen, then, in addition to the monophosphine species with complexation of the -O-i Pr group to the ruthenium, additional monophosphine propagating species may be observable due to oxygen in the polymer backbone chelating to the Ru center. Bisphosphine propagating species and RuCl 2(PCy3)2(dCH-o-O-i-PrC6H4), 3, are observable using 1 H NMR spectroscopy if PCy3 is added to 2 prior to the ROMP of 5-exo,6-endo-dicarbomethoxynorbornene, 4. The amount of added PCy3 is found to affect the relative intensities of the propagating bisphosphine species and 3 as well as the rate of monomer consumption and the polydispersity of the resulting polymer.

Dye-functionalized polymers via ring opening metathesis polymerization: principal routes and applications

“…Depending on the environment where the polymer will be applied in, esters as anchor groups might be subject to hydrolysis and could be replaced by ethers, amides, imides or aliphatic chains. However, one should consider that anchor groups have an influence on the polymerization rate [13,14] and monomers which are sterically unhindered bear the inherent risk of backbiting via a cross-metathesis mechanism leading to ill-defined polymeric products. In addition to the nature of the anchoring groups, the polymerization rate constants also depend on the stereochemistry on the norbornene and thus on the configuration of the substituents in 2-and 3-position (exo or endo).…”

“…In addition, copolymerization can improve the film-forming properties of electroactive compounds which was demonstrated for diphenylanthracene. While pure diphenylanthracene cannot be used in electroluminescent devices, the polymers prepared by Schrock et al (13) were successfully applied in organic lightemitting diodes (OLEDs). Similarly, 3,6-bis-(9,9-dihexyl-9H-fluoren-3-yl)-9-alkyl-9H-carbazole (14) was used in ROMP polymers prepared with a [Ru] initiator leading to good film-forming properties, thermal stability and good device performance [36].…”

Ring Opening Metathesis Polymerization

“…Taking the values of activation parameters, it is assumed that there may exist active ruthenium in chelated form, which is proved in the following studies [28,36,45].…”

“…It is known from literature data that esters of 5-norbornene-2,3-dicarboxylic acid can chelate the active forms of ruthenium complex with carbonyl oxygen of ester group, thus, forming hexatomic intramolecular complex [36]. Therefore, two active forms of ruthenium complex can take part in the polymer chain-growth reaction ( Figure 13).…”

Synthesis, Characterization and Radical Scavenging Ability of 3,5-di-tert-Butyl-4-hydroxyphenoxy-Functionalized Polynorbornenes Synthesized Using Ring-Opening Metathesis Polymerization

“…The PCy 3 dissociation is a crucial step to provide a available coordination site for binding approaching monomer and formatting metallacyclobutane intermediate. However, this coordination site could be occupied by formation of an intramolecular complex between the ruthenium center and the oxygen atom in the adjacent carbonyl, which should prevent the propagation of the living chain [13,14]. Therefore, it was no doubt that the ROMP activity of norbornene monomers associated closely with the amount and the steric position of oxygen-containing substituent.…”