G. N. Mukherjee

Mixed ligand complex formation of FeIII with boric acid and typical N-donor multidentate ligands

Equilibrium study of the mixed ligand complex formation of FeIII with boric acid in the absence and in the presence of 2,2′-bipyridine, 1,10-phenanthroline, diethylenetriamine and triethylenetetramine (L) in different molar ratios provides evidence of formation of Fe(OH)2+, Fe(OH)2+ , Fe(L)3+, Fe(H2BO4),Fe(OH)(H2BO4), Fe(OH)2(H2BO4)2-, Fe(L)(H2BO4) and Fe2(L)2(BO4)+ complexes. Fe(L)23+, Fe(L)2(H2BO4) and Fe2(L)4(BO4)+ complexes are also indicated with 2,2′-bipyridine and 1,10-phenanthroline. Complex formation equilibria and stability constants of the complexes at 25 ± 0.l°C in aqueous solution at a fixed ionic strength,I = 0.1 mol dm-3 (NaNO3) have been determined by potentiometric method.

Mixed-ligand complex formation equilibria of CuII with biguanide in presence of glycine as the auxiliary ligand

Equilibrium study on the mixed ligand complex formation of CuII with biguanide(Bg) and glycine (HG), indicated the formation of the complexes: Cu(Bg)2+, Cu(Bg)22+, Cu(Bg-H)(Bg)+, Cu(Bg-H)2, Cu(Bg)(OH)+, Cu(Bg-H)(OH); Cu(G)+, Cu(G)(OH), Cu(G)2; Cu(G)(Bg)+, Cu(G)(Bg-H); (G)Cu(Bg)Cu(G)2+, (G)Cu(Bg-H)Cu(G)+, and (G)Cu(Bg-2H)Cu(G). From the deprotonation constants of coordinated biguanide (Bg) in the complexes Cu(Bg)(OH)+, Cu(Bg-H)(Bg)+ and Cu(G)(Bg)+, the Lewis basicities of the coordinated ligand species (Bg-H)-, OH- and glycinate (G-) were found to be of the order: (Bg-H)-≫ OH- > G-. Bridging (N1-N4, N2-N5) tetradentate mode of coordination by biguanide species Bg, (Bg-H)- and (Bg2H)2- was indicated from the occurrence of biguanide-bridged dinuclear mixed ligand complexes (G)Cu(Bg)Cu(G)2+, (G)Cu(Bg-H)Cu(G)+, (G)Cu(Bg-2H)Cu(G) in the complexation equilibria.

Fac-mer equilibria of coordinated iminodiacetate (IDA2−) in ternary CuII(ida)(H−1B)− complex formation (B = imidazole, benzimidazole) in aqueous solution

AbstractpH potentiometric and spectrophotometric investigations on the complex formation equilibria of CuII with iminodiacetate (ida2−) and heterocyclic N-bases, viz. imidazole and benzimidazole (B), in aqueous solution in binary and ternary systems using different molar ratios of the reactants indicated the formation of complexes of the types, Cu(ida), Cu(ida)(OH)−, (ida)Cu(OH)Cu(ida)−, Cu(B)2+, Cu(H-1B)+, Cu(ida)(H−1B)−, (ida)Cu(B)Cu(ida) and (ida)Cu(H−1B)Cu(ida)−. Formation constants of the complexes at 25 ±1° at a fixed ionic strength,I = 0.1 mol dm−3 (NaNO3) in aqueous solution were evaluated and the complex formation equilibria were elucidated with the aid of speciation curves. Departure of the experimental values of the reproportionation constants(ΔlogKcu) of ternary Cu(ida)(H−1B)− complexes from the statistically expected values, despite their formation in appreciable amounts at equilibrium, were assigned tofac(f)-mer(m) equilibria of the ida2− ligand coordinated to CuII, as the N-heterocyclic donors, (H−1B)−, coordinatetrans- to the N-(ida2−) atom in the binary Cu(ida)f complex to form the ternary Cu(ida)m(H−1B)− complexes

Equilibrium study on the reactions of boric acid with somecis-diaqua CrIII-complexes

Substitution inertcis-diaqua CrIII complexes: cis-[(Lx−)CrIII(H2O)2](3−x)+ derived from N-donor ligands (Lx−) viz., bipyridine and 1,10-phenanthroline (x = 0) and N,O-donor ligands viz., nitrilotriacetate and anthranilate N,N-diacetate (x = 3) titrate as diprotic acids in aqueous solution and enhance the acidity of otherwise weakly acidic boric acid (H3BO3) producing mononuclear and binuclear mixed ligand CrIII-borate complexes: [(L)Cr(H2BO4)]x− and [(L)Cr(BO4)Cr(L)](1−2x)+ respectively through coordination of the H2O and/or OH− ligands, cis-coordinated in the CrIII-complexes on the electron deficient BIII-atom in H3BO3 with release of protons. Deprotonation of the parent CrIII-complexes and their reactions with H3BO3 have been investigated by potentiometric method in aqueous solution,I = 0.1 mol dm−3 (NaNO3) at 25 ±0.1°C. The equilibrium constants have been evaluated by computerized methods and the tentative stoichiometry of the reactions have been worked out on the basis of the speciation curves