Murahashi Coupling Polymerization: Nickel(II)–N-Heterocyclic Carbene Complex-Catalyzed Polycondensation of Organolithium Species of (Hetero)arenes

Revisiting Murahashi coupling, we found that it effectively allows polymerization of lithiated (hetero)­arenes by nickel­(II)-catalyzed polycondensation. Deprotonative polymerization of 2-chloro-3-substituted thiophene with <i>n</i>-butyllithium gave head-to-tail-type poly­(3-substituted thiophene). Poly­(1,4-arylene)­s were obtained by the reaction of the corresponding dibromides through lithium–bromine exchange. A lithiated thiophene derivative obtained via deprotonative halogen dance also underwent polymerization to afford a bromo-substituted polythiophene

Synthesis of Poly(3-substituted thiophene)s of Remarkably High Solubility in Hydrocarbon via Nickel-Catalyzed Deprotonative Cross-Coupling Polycondensation

Polythiophenes bearing a siloxane moiety in a substituent at the 3-position are prepared by deprotonative polycondensation of 2-bromo-3-substituted-thiophene with a bulky magnesium amide chloromagnesium 2,2,6,6-tetramethyl­piperidine-1-yl lithium chloride salt (TMPMgCl·LiCl) catalyzed by a nickel complex. Deprotonation takes place at 60 °C for 1 h to form the corresponding thiophene magnesium species, which is subjected to the polymerization by addition of 0.1–5 mol % NiCl₂(PPh₃)­IPr (IPr: 1,3-bis­(2,6-diisopropyl­phenyl)­imidazole-2-yl). Polymerization proceeds in a highly regioregular manner, and the molecular weight of the thus-obtained polymer is controllable by the ratio of monomer feed/catalyst loading to indicate <i>M</i>_n of up to 280 000 with narrow molecular weight distribution. Chloro­thiophenes are also found to induce polymerization in a deprotonative manner with TMPMgCl·LiCl or <i>n</i>BuLi (the Murahashi coupling polymerization). The obtained polymers bearing a siloxane moiety in the substituent is revealed to be dissolved in a hydrocarbon allowing formation of thin film from hexane