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, β_n, 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.

Graphical Abstract

A spectrophotometric investigation into the complexation of palladium(II) with thiocyanate revealed the existence of five coordinated palladium(II) complexes. Molar absorbance spectra as well as formation constants were calculated for all five complexes.

Keywords:

• Palladium(II)
• Thiocyanate
• Complexation
• Formation constants
• Spectrophotometry

Acknowledgement

This investigation was made possible by the generous financial support of Anglo American Platinum Limited, which is greatly appreciated.