Research on carbon—carbon coupling reactions of haloaromatic compounds mediated by zerovalent nickel complexes. Preparation of cyclic oligomers of thiophene and benzene and stable anthrylnickel(II) complexes

Dehalogenative carbon—carbon coupling reactions of 3,4-dibromothiophene, 1,2-dihalobenzenes and 9-bromoanthracene using zerovalent nickel complexes as a dehalogenating reagent produced respectively cyclotetrathiophene, triphenylene and 9,′9-bianthracene in good yields. However, two extremely stable arylnickel(II) complexes, Ni(10-X-9-anthryl)X(PPh3)2 (X = Br,Cl), where the 10-CX bond in the anthryl groups was inert against excess Ni0 complexes, were obtained by oxidative addition of 9,10-di- haloanthracenes to the Ni0 complexes. Under similar reaction conditions9,10-dihaloanthracenes did not undergo carbon—carbon coupling reactions.