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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 16, Number 3
BKCSDE 16(3)
March 20, 1995 

Effect of Uncoordinated Tertiary Nitrogen Atoms in Hexaaza Macrocyclic Nickel(Ⅱ) Complexes on Axial Binding of Anions and Water in Acidic Solutions
Seong-Jin Kim, Jang-Sik Choi, Shin-Geol Kang*, Chang-Su Kim, Myunghyun Paik Suh
Axial coordination of anions or water to the square-planar nickel(Ⅱ) complexes of the hexaaza macrocyclic ligands 1, 2, and 3, which contain two extra uncoordinated tertiary nitrogens, have been investigated in aqueous solutions containing HX (X=Cl-, Br-, NO3-, or ClO4-) and/or NaX. The nickel(Ⅱ) complexes exist in the acidic solutions as equilibrium mixtures of the square-planar [Ni(L)]2+ (L=1, 2, and 3) and octahedral species [Ni(H2L)X2]2+ (H2L=diprotonated form of L). Some octahedral complexes have been isolated and characterized. The solution behaviors of the complexes indicate that the formation of the octahedral complexes are significantly promoted by the protonation of the uncoordinated tertiary amines. The proportion of the octahedral complexes depends on the type of acid, and increases in the order of HBr < HNO3 < HCl.
217 - 221
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