Borate complexes in solution. Part-III. Mixed ligand complex formation of cobalt-, nickel- and zinc(II) with boric acid and some (N ,N) bidentate ligands

Department of Chemistry, University of Calcutta, University College of Science, 92 Acharya Prafulla Chandra Road Kolkata-700 009, India

E-mail : gurunath@cucc.ernet.in             Fax : 91-033-351-9755

Manuscript received 4 September 2000, revised 23 February 2001, accepted 12 May 2001

Equilibrium study on the mixed ligand complex formation of Co^II, Ni^II and Zn^II, hereafter M(II), with boric acid and some (N,N) bidentate ligands, viz. 2,2'-bipyridine 1,10-phenanthroline and ethylenediamine provides evidence of formation of binary M(N,N)²⁺, M(H2BO4)^- and ternary mononuclear M(N,N)(H2BO4)^- and binuclear M₂(N,N)₂(BO4)^- complexes in solution. Formation constants of the complexes at 25 ± 0.1^° have been determined in aqueous solution at a fixed ionic strength. I = 0.1 M (NaNO₃) and correlated with electronic structure, stereochemistry of metal ions and metal-ligand n-bonding. Complex formation equilibria have been elucidated with the aid of specification curves.