The composition and stability constants for the thiocyanato-N-hydroxyethylethylenediainine-N, N', N'-triacetato complexes of nickel(II), copper (II) and cobalt(II)

Abstract

The composition of the thiocyanato-N-hydroxyethylethylenediamine-N, N', N'-triacetato complexes of nickel (II), copper(II), and cobalt(II) was M(edtaOH)-(NCS)^2-. The stability constants of these complexes are 5.6, 2.1, and 1.6 for nickel(II), copper(II), and cobalt(II), respectively, at 25°C in 1.0 M NaClO₄. Thiocyanate ion may coordinate to metal through nitrogen atom. The molar extinction coefficients of Ni(edtaOH)-(NCS)^2- and Co(edtaOH)(NCS)^2- in the visible range are larger than those of Ni(edtaOH) (H₂O)^-and Co-(edtaOH) (H₂O)^-, respectively. However, the molar extinction coefficient of Cu(edtaOH)(NCS)^2- is smaller than that of Cu(edtaOH) (H₂O^)- at shorter wavelengths than 828 nm.