ScienceAsia 8 (1982): 147-166 |doi: 10.2306/scienceasia1513-1874.1982.08.147

STABILITY CONSTANTS OF POLYNUCLEAR COMPLEX IONS OF SOME FIRST-ROW TRANSITION ELEMENTS

SOONTAREE BENJARVONGKULCHAI^a and RODERICK D. CANNON^b

ABSTRACT: Cis-[Co(III)(en₂)(OH₂)⁺ and cis-[Cr(III)(en₂)(OH₂)⁺ can be regarded as ligands capable of being co-ordinated to metal ions through oxygen atoms forming a series of polynuclear complexes with the general formula: {cis-[M(III)(en₂)(OH₂)⁺}_nM' (where M(III) = Co(III) or Cr(III) and M' = metal ions). The stability constants of the polynuclear complexes: {cis-[Co(III)(en₂)(OH₂)⁺}M' and {cis-[Cr(III)(en₂)(OH₂)⁺}M' in which M' was Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cr(II)(Cr(III) complex ligand only) and Fe(II)(Cr(III) complex ligand only) were determined using a pH titration method. Both sets of stability constants follow the Irving- Williams sequence of stability constants. Comparison of the two sets of stability constants shows that the polynuclear complexes belonging to cis-[Co(III)(en₂)(OH₂)⁺ are more stable than those belonging to cis-[Cr(III)(en₂)(OH₂)⁺, which is in agreement with the fact that the acid. dissociation constants of cis-[Co(III)(en₂)(OH₂)⁺ are smaller than those of cis-[Cr(III)(en₂)(OH₂)⁺.

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a Department of Chemistry, Faculty of Science, Silpakorn University, Nakorn Pathom Thailand
b School of Chemical Sciences, University of East Anglia, Norwich, England.

Received 26 May 1982