Dehalogenative or Deprotonative? The Preparation Pathway to the Organometallic Monomer for Transition-Metal-Catalyzed Catalyst-Transfer-Type Polymerization of Thiophene Derivatives

A Ni0(cod)(dq) (COD: 1,5-cycloctadiene; DQ: duroquinone) complex as a catalyst precursor for oligothiophene and polythiophene synthesis

Nickel-catalyzed syntheses of oligothiophene and polythiophene were carried out with Ni(cod)(dq) (COD: 1,5-cycloctadiene; DQ: duroquinone) as a catalyst precursor. Studies on the ligand exchange of Ni(cod)(dq) revealed that a high temperature was necessary to replace COD and DQ with PPh3 and N-heterocyclic carbene IPr. A coupling reaction of a metalated 3-hexylthiophene with 2-chloro-3-hexylthiophene employing Ni(cod)(dq) with IPr proceeded with a remarkably reduced amount of homocoupling byproduct. Polymerization of 2-chloro-3-hexylthiophene with Ni(cod)(dq)/DPPP also resulted in the reduction of the regioregularity defect.

Nickel-Catalyzed Direct Arylation Polymerization for the Synthesis of Thiophene-Based Cross-linked Polymers

An earth-abundant nickel(II) bipyridine catalyst, combined with lithium hexamethyldisilazide as base, demonstrates its wide applicability in the direct arylation polymerization of di- and tri-thiophene heteroaryls with poly(hetero)aryl halides. With a nickel catalyst loading of 2.5 mol%, a series of twenty highly cross-linked organic polymers is obtained in 34 to 99 % yields. Using mixed polytopic coupling partners allows obtaining alternating and optically active thiophene-based solids with intrinsic porosity.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.