H. Irving, P. Gee
Jul 1, 1971
Citations
0
Influential Citations
5
Citations
Journal
Analytica Chimica Acta
Abstract
Abstract 2-Chloro-1,10-phenanthroline (L) readily accepts one proton on the 10-nitrogen atom and in strongly acidic media a second proton on the 1-nitrogen atom. Stoicheiometric acid dissociation constants p K 1 H =4.27 and p K 2 H =0.22 for the species HL + and H 2 L 2+ were obtained from spectrophotometric measurements in aqueous buffers at 25° and I =0.1 M(KCl). Partition coefficients were determined for the uncharged base between water and n -hexane, carbon tetrachloride, and chloroform, and the stepwise formation constants of metal complexes were obtained from similar measurements with salt solutions. Stabilities increased in the order Fe Zn and, when due account is given to differences in ligand basicities, steric hindrance to complex-formation is about the same as that due to a 2-methyl substituent. In the iron(II) complex, K 3 #62; K 1 , K 2 , an anomaly previously found only with 2,2'-bi-pyridine and 1,10-phenanthroline.