Ethylenediamine, formation constants with

The equilibrium formation constants for the 1 1 complexes of Hf with glycine and serine in solutions of pH 2 have been determined as 31 and 18, respectively, and the HfO -amygdalic acid complex, [HfO PhCH(0)- 02)2] , has been obtained in aqueous solutions of pH 7—10.5. The stability constants of the 1 1 complexes of ZrO with iVh/ -ethylenediamine-bis(succinic acid) and Nh/ -ethylenediaminebis(glutaric acid) have been determined. ... 

Formation constants for 1 1 and 2 1 Ag1 complexes with ethylenediamine Schiff bases of the type RCH=NCH2CH2N=CHR, have been reported (Table 53).392 Based on the higher stability of the pyridyl derivative, it was claimed that the pyridyl N participated in the coordination. 

The formation constant of the silver-ethylenediamine complex, Ag(NH2CH2CH2NH2), is 5.0 X 1(T. Calculate the concentration of Ag" in equilibrium with a 0.10 M solution of the complex. (Assume no higher order complexes.)... 

Silver ion forms a stepwise 1 2 complex with ethylenediamine (en) with formation constants of = 5.0 X 10 and Kf2= 1.4 X 10. Calculate the solubility of silver chloride in 0.100 M ethylenediamine. Also calculate the equilibrium concentrations of Aglen)" and Ag(en)2 . ... 

Calculate the solubility of AgCl in 0.100 M ethylenediamine. Compare with Problem 6. The formation constant is given in Problem 6. 

Other polydentate ligands are polyamines and related ligands. Stability constants of silver(I) complexes with polyamines in dimethyl sulfoxide,419 A-methyl-substituted 4-methyldiethylene-triamines,420 or ethylene- or N- or C-methylated ethylenediamine in aqueous solution have been reported.421 The structure of the silver 1,3-diaminopropane complex, [Ag NH2(CH2)3NH2 ]-C104,422 and complex formation with 1,4-diaminobutane and 1,5-diaminopentane have been reported.423 A dinuclear silver(I) compound with ethylenediamine [(enH)Ag(en)Ag(enH)2]4+ has... 

A measure of the Lewis acidity of a metal ion is determined by its affinity for a pair of electrons, and the greater this affinity, the more stable the complexes formed by the metal ion will be. However, removing electrons from a metal to produce an ion is also related to the attraction the metal atom has for electrons. Therefore, it seems reasonable to seek a correlation between the stability constants for complexes of several metals with a given ligand and the total energy necessary for ionization to produce the metal ions. The first-row transition metal ions react in solution with ethylenediamine, en, to form stable complexes. We will consider only the first two steps in complex formation, which can be shown as follows ... 

Eichhom and his co-workers have thoroughly studied the kinetics of the formation and hydrolysis of polydentate Schiff bases in the presence of various cations (9, 10, 25). The reactions are complicated by a factor not found in the absence of metal ions, i.e, the formation of metal chelate complexes stabilizes the Schiff bases thermodynamically but this factor is determined by, and varies with, the central metal ion involved. In the case of bis(2-thiophenyl)-ethylenediamine, both copper (II) and nickel(II) catalyze the hydrolytic decomposition via complex formation. The nickel (I I) is the more effective catalyst from the viewpoint of the actual rate constants. However, it requires an activation energy cf 12.5 kcal., while the corresponding reaction in the copper(II) case requires only 11.3 kcal. The values for the entropies of activation were found to be —30.0 e.u. for the nickel(II) system and — 34.7 e.u. for the copper(II) system. Studies of the rate of formation of the Schiff bases and their metal complexes (25) showed that prior coordination of one of the reactants slowed down the rate of formation of the Schiff base when the other reactant was added. Although copper (more than nickel) favored the production of the Schiff bases from the viewpoint of the thermodynamics of the overall reaction, the formation reactions were slower with copper than with nickel. The rate of hydrolysis of Schiff bases with or/Zw-aminophenols is so fast that the corresponding metal complexes cannot be isolated from solutions containing water (4). 

---