Thermochemical Studies on Metal Complexes. VI. The Formation of Some Cadmium(II) Complex Systems at Different Ionic Strengths.

Impact of Ligand Protonation on Higher-Order Metal Complexation Kinetics in Aqueous Systems

“…Cd(II)−PDCA solutions in the pH range 3.7−5.1 were buffered with 5 × 10 -3 mol dm -3 acetic acid (Prolabo, Rectapur)/sodium acetate (Janssen Chimica, pure), and buffering at pH 6.0 was effected with 0.01 mol dm -3 (2-( N -morpholino)-ethanesulfonic acid (MES, Fluka, MicroSelect, ≥99.5%). Acetate and MES have low affinity for Cd(II), and, in the presence of PDCA, there is negligible complexation by the buffer components: for acetate, the stability constants for Cd(II) complexation are log K 1 = 1.26, log K 2 = 0.74, and log K 3 = 0.70, and no binding of Cd(II) by MES was observed up to buffer concentrations of 0.1 mol dm -3 . Ni(II)−bicine solutions in the pH range 7.0−7.8 were buffered with Na 2 HPO 4 (Fluka, MicroSelect, >99.0%)/KH 2 PO 4 (Fluka, puriss p.a., >99.5%), and solutions at pH 8.3 were buffered with 2-amino-2-hydroxymethyl-1,3-propanediol (Tris buffer, Fluka, BioChemika, >99.0%).…”

Ultrasonic absorption study of the complex formation of zinc(II) chloroacetate and n-butyrate in aqueous solution

“…Considerable information on metal-complexation kinetics in aqueous solution has now been accumulated.1•2 However, comparatively less information is available on the substitution rate on zinc and cadmium ions. In earlier ultrasonic absorption studies, particular interest has been directed to those on zinc(II) sulfate, where Maass,4 Petrucci and his co-workers,5 and Fritsch et al 6 obtained the values in the range (1-7) X 107 s-1 (at [20][21][22][23][24][25] °C) for the rate constant of substitution on the metal; the result of Bechtler et al yields a much higher value of 6 X 10s s-1 (at 20 °C).7 For the complexation of zinc(II) acetate, Maass obtained the value 3 X 107 s-1 (at 20 °C). 4 A temperature-jump study by Miceli and Stuehr8 for zinc(II) glycinate gave 7 X 107 s-1 (at 25 °C) and that by Rorabacher9 for zinc(II) monoammine complex 2 X 107 s-1 (at 11 °C).…”

The structures of the mixed complexes cadmium(II)–1,4,10,13-tetraoxa-7,16-diazacyclooctadecane diiodide and mercury(II)–1,4,10,13-tetraoxa-7,16-diazacyclooctadecane diiodide

“…I-is a well known complexing agent which forms very stable complexes particularly with the soft Hg 2÷ (Gerding, 1968;Sill6n, 1949). A solution-chemical investigation of these complexes is in progress.…”