ChemInform Abstract: Stability of the Complex of Nickel(II) with Cyclam

The formation constant for the Ni(II) complex of cyclam (1,4,8,11-tetraazacyclododecane) was measured by an out-of-cell technique to be 20.1 ± 0.5 in 0.5 M NaCl at 25 °C. This is somewhat less than the value of 22.2 reported by D. Hinz and D. W. Margerum, Inorg. Chem., 13 (1974) 2941. The new log K 1 for Ni(II) with cyclam is more reasonable in relation to the log K 1 values observed for other tetraazamacrocycle complexes of Ni(II), and also other metal ions. Possible reasons for the difference between the value for log K 1 reported here and Margerum's value are discussed.