Ethylenediamine zinc complexes

Di-t-butyl phosphate complexes of zinc were synthesized as precursors for ceramic material formation. A tetrameric zinc complex was characterized from the treatment of zinc acetate with the phosphate resulting in a compound with a bridging oxo at the center, [Zn4(/i4-0)(di-t-butyl phosphate)6]. In the presence of auxiliary donor ligands such as imidazole or ethylenediamine, monomeric complexes are formed, [Zn(di-t-butyl phosphate)2(imidazole)4]. It is also possible to convert the tetramer into the monomer by treating with a large excess of imidazole.41... 

A series of complexes of the type ML(SCN) (C104)2-, (M - Zn, Cd, or Hg x = 1 or 2) has been prepared where L is en and its tetramethyl derivative, diethylenetriamine and its pentamethyl derivative, triethylenetetramine and its hexamethyl derivative, and bis(ethylenediamine). The complexes are either monomeric with four-, five- or six-coordinate metal, or polymeric containing bridging thiocyanate the perchlorate is always ionic. The thiocyanate is generally bonded through nitrogen to zinc and cadmium (and through sulfur to mercury).181... 

Complexes of zinc chloride and perchlorate with the carcinogenic N, A -/3-chloroethyl-ethylenediamine have been reported.1218 The solvolysis rates of the free ligand and of the zinc complex have been studied by NMR spectroscopy. 

Kanemura, Y., and Watters, J.I., Acidimetric studies of cadmium and zinc complexes with ethylenediamine, oxalate, and their mixtures using the glass electrode. J. Inorg. Nucl. Chem. 1701-1709 (1967). 

Carbamic acid, (2-aminoethyl)-. See Ethylenediamine carbamate Carbamic acid, (6-aminohexyl)-. See Hexamethylenediamine carbamate Carbamic acid, ammonium salt. See Ammonium carbamate Carbamic acid, 1H-benzimidazol-2-yl-. See Benzimidazole carbamate Carbamic acid, butyl-3-iodo-2-propynyl ester. See lodopropynyl butylcarbamate Carbamic acid, compd. with 1,2-ethanediamine Carbamic acid, compd. with ethylenediamine. See Ethylenediamine carbamate Carbamic acid, dibutyidithio-, zinc complex. 

An octahedral zinc complex without water molecules is found" in tris-(ethylenediamine)zinc thiosulphate, in which the Zn ion is bonded to three chelating ethylenediamine groups. The Zn-N bonding is unsymmetrical, with three at 2.209 A and three at 2.29 A. A similar cadmium species is described in which the anion is selenosulphate. The same asymmetry in metal-nitrogen bonds is found, with three Cd-N distances at 2.09 A and three at 2.S8 A. 

In 1965, Breslow and Chipman discovered that zinc or nickel ion complexes of (E)-2-pyridinecarbaldehyde oxime (5) are remarkably active catalyst for the hydrolysis of 8-acetoxyquinoline 5-sulfonate l2). Some years later, Sigman and Jorgensen showed that the zinc ion complex of N-(2-hydroxyethyl)ethylenediamine (3) is very active in the transesterification from p-nitrophenyl picolinate (7)13). In the latter case, noteworthy is a change of the reaction mode at the aminolysis in the absence of zinc ion to the alcoholysis in the presence of zinc ion. Thus, the zinc ion in the complex greatly enhances the nucleophilic activity of the hydroxy group of 3. In search for more powerful complexes for the release of p-nitrophenol from 7, we examined the activities of the metal ion complexes of ligand 2-72 14,15). 

Ferrocene-containing sulfur ligands have been used in complex formation with zinc. 3-Ferro-cenyl-3-mercaptopropenale and l,l -bis(3-mercaptopropenale)ferrocene (112) form stable complexes as do their Schiff base derivatives with aniline or 1,2-ethylenediamine. The Fen/Fein redox couple shows only minor metal dependence, this is attributed to tetrahedral distortion.884... 

Only 45 ml. of ethylenediamine is needed if the solution contains no zinc, f Formation of polynuclear coordination complexes by means of hydroxyl groups as bridging ligands. 

Chiu prepared monodisperse crystalline particles of metal sulfides, such as lead sulfide (PbS cubes 100 A) (I), cupric sulfide (CuS hexagonal bipyramids 200 A) (2), and zinc sulfide (ZnS multifaceted spheres 0.1-0.4 p,m) (3) by introducing hydrogen sulfide gas into dilute acidic solutions of the ethylenediamine tetraacetic acid (EDTA) complexes of the corresponding metal ions (10 4-10-1 mol dm-3) for several minutes at room temperature. 

As early as 1972, Sigman and Jorgensen used a ternary zinc(II) complex of iV-(2-hydroxyethyl)ethylenediamine 4 and 4-nitrophenyl pi-colinate 5 as a model for Znn-alkoxide-promoted transesterification (see Scheme 1) (16). Although the Znn-bound alkoxide (its pKa kinetically determined to be 8.4) was shown to be a possible reactive species to give 6, the subsequent hydrolysis for completion of the ester hydrolysis as well as the catalytic cycle failed. 

Sigman and Jorgenson490 have found that zinc(II) catalyzes the transesterification reaction between N- (/3-hydroxy ethyl) ethylenediamine and 4-nitrophenyl picolinate. This reaction involves a reactive mixed ligand complex (152) in which the zinc(II) ion perturbs the p/fa of the hydroxyethyl group of N-(/3-hydroxyethyl)ethylenediamine to provide a high effective concentration of the nucleophile. Intramolecular nudeophlic attack then occurs at the carbonyl group of p-nitrophenyl picolinate. This system provides a somewhat unique example of intramolecular... 

The difficulty in obtaining this monomer in the pure state arises from the fact that the known methods of preparation involve the simultaneous formation of considerable amounts of the isomers of spiropentane which are difficult to remove. The method adopted as giving the most satisfactory yields is that of Applequist, Fanta, and Henrickson (I, 2). The spiropentane is prepared by reaction of zinc dust with pentaerythrityl tetrabromide in alcohol in presence of the sodium salt of ethylenediamine-tetraacetic acid as complexing agent. The yield of hydrocarbon (spiropentane plus various ethylenic compounds) is of the order of 84%. The spiropentane is obtained in the pure state by treating the mixture with bromine in dibromomethane. The yield of pure spiropentane was found to be 62%. 

It has been found4 that a good yield may be obtained rapidly by allowing the commercially available green chromic chloride, CrCl8-6H20, in methanol to boil under reflux with ethylenedi-amine in the presence of metallic zinc. The product, hydrated tris(ethylenediamine)chromium(III) chloride, is obtained as a solid and is readily purified. An exactly similar procedure may be used for the complex of 1,2-propanediamine. 

A novel class of nucleic acid mimics has been described which possess two ethylenediamine moieties for intermolecular metal co-ordination (25). In the presence of Zn + ions and template DNA, the analogues (25) form relatively stable structures, stabilised by the co-ordination of adjacent chelating moieties with zinc ions. It was shown that with an oligothymidine template and the adenine derivative of (25) that a 2 1 complex was formed, which showed a biphasic melting transition. Short RNA duplexes (3-4 bp) are considerably stabilised if both termini of the duplexes are bridged by non-nucleotidic linkers. For example, the pairing of rGAA with rUUC in such a cyclic system exhibits a Tm of 36°C in IM salt solution. 

Salts of the three metals form ammines, principally tetrahedral complex ions of the form [M(NH3)4]2+, but in addition mercury salts form linear, diammine complexes, and zinc and cadmium octahedral hexa-ammines, [M(NH3)g]2+. Ethylenediamine produces 6-co-ordinate complexes, [M(en)3]2+, with all three cations. 

Charles (1954) has compared the entropy of ethylenediamine-tetraacetate (EDTA) complex formation for several elements, including zinc, and finds the entropy change to be a linear function of the partial molal entropy of the complexed metal. In Fig. 10, the entropy changes in the formation of ammonia (Williams, 1954), ethylenediamiue (En) (Davies et al., 1954), and EDTA (Charles, 1954) complexes of Zn, Cu, and Cd are plotted as a reciprocal of the ionic radius minus a term containing the molecular weight (Powell and Latimer, 1951), as a measure of the partial molal entropy of the cations. The AS° values plotted are for the reaction ... 

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