Evidence for Catalyst Association in the Catalyst Transfer Polymerization of Thieno[3,2-b]thiophene

Abstract

The performance of catalyst transfer polymerization (CTP) reactions which depend on catalyst association was studied on 3,6-dioctylthiothieno[3,2-b]thiophene (TT)-monomers. This monomer was selected because a strong association of the catalyst is expected, since the aromaticity of thienothiophene is largely maintained when the catalyst and thienothiophene associate. This study includes both reported and unreported Ni-and Pd-catalyst systems. It is found that no polymer formation can be observed using Ni-catalysts, whereas Pd-catalysts show a similar behavior as for other monomer systems. During the study of the Ni-catalyzed CTPs, the π-associated Ni 0 -complex has been isolated in situ and displayed a high stability in solution. It is shown that the associated complex interferes with the polymerization reaction and even prevents polymer formation. Furthermore, this complex prevented any Kumada-coupling reaction in the presence of the TT unit, as it serves as a "trapping site" for free Ni 0 -catalyst entities. Ni 0 -trapping does not occur during polymerization of 3-alkylthiophene, confirming the presence of the π-associated Ni 0 -complex in this polymerization. This introduces a new convenient method of probing Ni 0 -association during all Ni-catalyzed reactions. Furthermore, these results establish the presence of an upper limit to the catalyst association strengthabove which oxidative addition is prevented and the polymerization is inhibitedand they therefore add extra considerations for optimal catalyst design.

Nickel-Catalyzed Suzuki Polycondensation for Controlled Synthesis of Ester-Functionalized Conjugated Polymers

“…The stronger Ni binding interaction as compared to Pd may be important for achieving enhanced control in chain-growth polymerizations. 7 Ni-catalyzed Suzuki cross-coupling to form biaryl compounds has been reported with relatively mild reaction conditions and moderate catalyst loadings. 6c This led us to investigate the possibility of Suzuki CTP with π-accepting ester groups as the side chain substituent.…”

Investigation of Bimetallic Nickel Catalysts in Catalyst‐Transfer Polymerization of π‐Conjugated Polymers

“…This is due to the Ni(0) catalyst remaining adhered to the polymer chain, preventing “ring‐walking” from occurring. Very stable metal π‐aryl complexes have been observed with polymerizations of thiophene‐benzothiadiazole‐thiophene, thienothiophenes, and p ‐phenylene vinylene monomers . The ligand to metal donation of the benzene amino ligand may be weaker if the aniline moiety is not donating electron density toward the phosphine group.…”

Termination reaction of living poly(3-hexylthiophene) using thiophene Grignard reagents: Substituent effect on the functionalization

“…38 On the contrary, the TM of GT1 and the following RE can smoothly take place in the termination reaction of the KCTP because the divalent nickel complex is already present at the propagating end, which eventually lead to the carbon-carbon bond formation between hexylthiophene and methoxythiophene "without the intermolecular transfer" of the zero-valent nickel complex. We finally investigated the termination reaction of the KCTP using GT3·LiCl in the presence of the large amount of styrene (1000 equivalent relative to the nickel catalyst) following to the report by Pickel et al 40 to obtain P3'-dppe-St having the number-averaged molecular weight of 6000 and the molecular weight distribution of 1.14.…”