HARD AND SOFT ACIDS AND BASES (HSAB): EVIDENCE OF ADDUCT FORMATION IN A NON-AQUEOUS SOLVENT MEDIUM INVOLVING SOME DIVALENT CLASS B METAL IONS IN CHEMISTRY

Abstract

The Lewis acid / base behavior of three divalent metal ions, namely, copper (II), lead (II), and Mercury (II), and two Lewis bases, namely, 2-naphthol and caffeine, has been investigated in a non-aqueous solvent, ethanol, using the method of continuous variation. A Job's plot of the absorbance data shows no maximum for the Cu (lI) system, indicating non-cooperative interaction in this system. Similar plots indicate that each of the two ions, namely, Pb (II) and Hg(II), interacts cooperatively with both 2-naphthol and caffeine in ethanol solvent; a maximum was obtained in the Job's plot for each system, yielding stoichiometries of 1:1 for the resulting adduct formed in each case. These data suggest that the Eigen-Wilkins mechanism may be applied to adduct formation involving the two class B Lewis acids used in these studies in a non-aqueous medium and which may thus form part of their characteristic chemical behaviour.