Complexation of palladium(II) with thiocyanate – a spectrophotometric investigation

Abstract

Complex-formation of Pd(II) with thiocyanate has been investigated by spectrophotometry at 25 °C and an ionic strength of 1.0 M. The formation constants, βn, for the palladium(II) thiocyanate complexes [Pd(SCN)n(H2O)4–n]2–n (n = 0–4), have been determined and the values are: log β1 = 8.14, log β2 = 15.46, log β3 = 21.94, and log β4 = 27.42. These complexes are generally accepted to be square planar. However, a five-coordinate species, i.e. [Pd(SCN5]3–, with a formation constant of log β5 = 31.94 seems to exist and is proposed to be square pyramidal. Molar absorption spectra for all the complexes in question have been obtained.