A convenient preparation of 2,2′:6′,2″:6″,2‴-quaterpyridine; the crystal and molecular structures of 2,2′:6′,2″:6″,2‴-quaterpyridine and bis(acetonitrile)-(2,2′:6′,2″:6″,2‴-quaterpyridine)nickel(II) hexafluorophosphate–acetonitrile(1/1)

Abstract

2,2′:6′,2″:6″,2‴-Quaterpyridine has been prepared in 40–45% yield by the nickel(0) coupling of a 6-halogeno-2,2′-bipyridine. The reaction initially yields a nickel(II) complex of 2,2′:6′, 2′:6″,2‴-quaterpyridine which may be demetallated by treatment with NaCN. The crystal and molecular structures of 2,2′:6′,2″:6″,2‴-quaterpyridine [monoclinic, a= 6.348(1), b= 8.179(2), c= 14.894(3)Å, β= 100.15(1)°, space group P2₁/n, Z= 2] and bis(acetonitrile)-(2,2′:6′,2″:6″,2‴-quaterpyridine)nickel(II) hexafluorophosphate-acetonitrile (1/1)[monoclinic, a= 22.348(9), b= 11.504(5), c= 15.636(6)Å, β= 128.41 (2)°, space group C2/c, Z= 4] have been determined. The free ligand is essentially planar with transoid arrangements of the pyridyl rings as observed in 2,2′-bipyridine. The nickel complex is approximately octahedral with the 2,2′:6′,2″:6″,2‴-quaterpyridine occupying the equatorial sites; the Ni–N distances to the terminal pyridine rings are longer than those to the inner rings.