The Standard Electrode Potentials of the Gold Aqua Ions and the Stabilities of Gold(l) and Gold(III) Complexes in Aqueous Solution.

Chemistry Department, Royal Veterinary and Agricultural University, DK-1871 Copenhagen V, Denmark.

Chemistry Department I. Inorganic Chemistry, The H. C. Orsted Institute,

University of Copenhagen, DK-2100 Copenhagen \( \phi\) Denmark.

The standard electrode potentials of the hypothetical diaqua gold(l) and tetraqua-gold(lll) ions are approximated by means of Edwards' equation redefined using stability data for the chlorido and bromido complexes as basis. The following values are recommended: E^o (Au(H₂O)₂ ⁺, Au)=1.83 V and E^o (Au(H₂O)₄ ³⁺, Au)=1.52 V. The use of the coefficient α in Edwards' equation as a softness parameter is discussed, and it is shown that it correlates well with Klopman's theoretical softness parameter. The softness or class (b) character increases in the order : Au(I) \(<\)Hg(II) \(<\)Au(III).