Electrochemical dehalogenation polycondensation of 2,5‐dibromopyridine mediated by nickel and palladium complexes

Abstract
Dehalogenation polycondensation of 2,5‐dibromopyridine, 2,5‐Br2‐Py, to poly(pyridine‐2,5‐diyl), PPy, has been achieved under electrochemical reductive conditions mediated by various nickel(II) and palladium(II) complexes (nickel‐2,2′‐bipyridine (bpy) and ‐phosphine complexes and palladium‐bpy complexes). PPy is obtained as a thin smooth film on a platinum electrode in high yield, and among the nickel and palladium complexes [Ni(bpy)3]2Br2 serves as the best mediator for the electrochemical reductive polycondensation. Carrying out the electrochemical polycondensation in a two‐compartment cell and in a one‐compartment cell gives almost the same results. The PPy film prepared by using the nickel(II) complex gives the same IR and cyclic voltammogram as chemically prepared authentic PPy shows. When PdCl2(bpy) is used as the mediator, the formation of PPy is accompanied by metalation reaction of palladium to PPy.

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