Application of “Transfer-Free” Suzuki Coupling Protocols toward the Synthesis of “Unambiguously Linear” Poly(p-phenylenes)

Abstract

Soluble derivatives of poly(p-phenylene) of high molecular weight were synthesized via Suzuki coupling reactions catalyzed by palladium(0) precursors in the presence of either triphenylphosphine (TPP) or tri(o-tolyl)phosphine (TOTP). Syntheses involving the former ligand resulted in the formation of polymers in which the incorporation of phosphine was clearly observable by 31 P NMR. However, polymers formed utilizing the latter ligand in a hydrophobic solvent such as CH2Cl2 exhibited no signals in the 31 P NMR spectrum, even after 20 000 scans. Analyses by tandem GPC-light scattering and tandem GPC-light scattering-viscometry showed that polymers synthesized by utilizing a large amount of TPP-based catalyst (2%) possessed a considerably lower molecular weight than did the other samples and exhibited markedly different dependencies of the radius of gyration and intrinsic viscosity on molecular weight. From these studies, it does appear that the aryl-aryl interchange reaction known to occur in ArPdL2I complexes significantly affects the architecture of these polymers.

Semiconducting Thienothiophene Copolymers: Design, Synthesis, Morphology, and Performance in Thin‐Film Organic Transistors

“…Optimization of the crosscoupling conditions demonstrated that the use of bulky phosphine ligands such as tri(o-tolyl)phosphine, resulted in higher molecular weights than for less bulky ligands like triphenylphosphine, most likely due to the suppression of ligand transfer reactions that can occur to the growing polymer chain from less bulky ligands. [89] The use of microwave heating and sealed reaction tubes facilitated the reaction, enabling superheating of the solvent (chlorobenzene) and reducing reaction times from days to minutes. [90] Similar findings have been reported for the use of microwave heating in other polymerizations.…”

Preparation of poly(fluorene)s using trans‐bis(dicyclohexylamine)palladium diacetate as a catalyst: Scope and limitations

“…A way of overcoming long reaction times is the use of microwave-assisted coupling reactions. [33][34][35] Besides, aryl-aryl interchange reactions between palladiumand phosphine-bound aryls [36][37][38][39][40][41] can lead to an unwanted incorporation of phosphines into the polymer chain. Last but not least, Pd(PPh 3 ) 4 is air-sensitive.…”

Improved Suzuki polycondensation: A diiodo versus a dibromo monomer

“…Regarding SPC with diiodo monomers there are two reports in the literature. Based on earlier work by Percec 4) , Weder oligomerized diiodo benzene and a saturated bifunctional boron compound 5) and Novak polymerized a 4,49-diiodobiphenyl with a 4,49-biphenyl diboronic acid ester to give the corresponding high molecular weight poly(para-phenylene) 6) . Novak also found using Pd 2 (dba) 3 with P(o-tolyl) 3 as co-ligand that in this reaction no ligand derived phosphorus incorporation into the backbone takes place.…”