ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Protonation constants of methyliminobis(methylenephosphonic) acid and the stability-constants of its complexes

I. Lukeš and I. Dominák

Department of Inorganic Chemistry, Charles University, CS-128 40 Prague

Abstract: The protonation constants of methyliminobis(methylenephosphonic) acid (H₄mibmp) and the stability constants of its complexes with nine cat­ions have been determined at 25 °C and the ionic strength I(NaCl0₄) = 0.1 mol dm^-3 by Potentiometrie titrations (pK₁ < 2, pK₂ = 5.00, pK₃ = 6.22, pK₄ = 11.94). The data were treated using the MINIQUAD statistical pro­ gram. It has been verified that Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ form only the complexes of the type [Mmibmp]^2- (log{ß}=5.00 (Mg²⁺)-4.21 (Ba²⁺)). With the transition metal cations, Co²⁺, Ni²⁺, Zn²⁺, and Cd²⁺, the existence of the complexes of the types [Mmibmp]^2- , [Mmibmp₂]^6- and their protonated forms, [MHmibmp]^- and [M(Hmibmp)₂]^4- , has been confir­ med. The [Mmibmp₂]^6- complex has not been found in the systems contain­ ing copper. On the basis of the results, coordination through N-atoms is assumed only for the complexes with Cu²⁺ and Cd²⁺ . The other cations are probably coordinated only through the oxygen atoms.

Full paper in Portable Document Format: 423a311.pdf

Chemical Papers 42 (3) 311–317 (1988)