Poly 2,5-dibromo-3-alkylthiophene

Ni(dppp)Cl2 catalyst. Chen and Rieke [12] used an organozinc intermediate of 2,5-dibromo-3-alkylthio-phene which in the presence of catalytic amounts of Ni(dppp)Cl2 gave regioregular poly(3-alkylthiophene). The degree of regioregularity, determined on the basis of the aromatic H signal in H NMR, in both cases exceeded 97%. 

General Preparation of Regioregular HT Poly(3-Alkylthiophenes) from 2,5-Dibromo-3-Alkylthiophenes Preparation of Regioregular HT Poly(3-Hexylthiophene] (4b)... 

Regioregular poly(3-alkylthiophene) was prepared by the coupling of 2-bromo-5-(halogenozincio)-3-hexyl-thiophene witii a nickel catalyst [110]. Zn, active zinc, was prepared by adding zinc chloride in tetrahydrofuran to finely cut lithium and a catalytic amount of naphthalene under argon atmosphere. The reaction mixture was stirred until the lithium was consumed. The resulting black suspension of active zinc was used for the preparation of (45). 2,5-Dibromo-3-hexylthio-phene was added to the active zinc at — 78°C. The mixture was stirred for 1 hour at this temperature and allowed to warm to 0°C in 3 hours. Ni(dppe) (0.2 mol%) was added at room temperature and the mixture was stirred for 24 hours at room temperature. Poly(3-hexylthiophene) was obtained in a 98% yield. The and Mw were 4 x 10 and 1.5 x 10" by GPC, respectively. When the polymer was extracted in a Soxhlet apparatus with methanol and then hexane, the yield decreased to 70-80% but the molecular weights sharply increased to 2.6 x 10" and 3.8 x 10 ... 

Dibromo-3-Alkylthiophenes Preparation of Regiorandom Poly(3-Hexylthiophene) (5b)... 

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