Hydroxamates metal complexes

Hydrosulfido complexes, 517 bonding, 519 reactivity, 519 structures, 519 synthesis, 518 types, 518 Hydroxamates metal complexes, 505-508 Hydroxamic acid, N-methyl-metal complexes, 507 Hydroxamic acid, phenyl-metal complexes stability, 506 Hydroxamic acids... 

Metal complexes of hydroxamic acid analogues. S. Mizukami and K. Nagato, Coord. Chem. Rev.,... 

Hydroxamic acids and their metal complexes. Y. K. Agrawal, Russ. Chem. Rev. (Engl. Transl.), 1979, 48, 948-963 (123). 

Dyrssen, D., Studies on the extraction of metal complexes. XXXII. N-phenylbenzo-hydroxamic acid, Acta Chem. Scand. 10, 353-359 (1957). 

Hydroxamic acids of general structure R—CO—NH—OH, having R as an organic residue, have been known since 1869 with the discovery of oxalohydroxamic acid by Lossen . Despite this, researches on these compounds were lacking until the 1980s, after which an enormous amount of information has accumulated with respect to their biomedical applications, synthesis, and the determination of the structures of their metal complexes. ... 

VII. Simple Metal, Simple Ligand Ga(III) Hydroxamates VIII. Simple Metal, Complex Ligand Mn(II) Carboxylates... 

The complexing capacity of hydroxamic acids was predicted by Werner in 1908, who also indicated the metals most likely to form stable complexes.288 Since then, the formation of poorly soluble and intensely coloured hydroxamates has been used for analytical determinations for a number of metal ions, such as Fe3+, Mos+, Vs+ etc. A recent general review of transition metal complexes of hydroxamic adds included the few known examples of silver(I) complexes.289... 

The preference of hydroxamic acids to form metal complexes through the hydroxamide functional group (1) and not through the hydroxyoxime structure (2) is confirmed by IR,27,28 UV,29 ESR30 and NMR28 spectral studies. Hydroxamic adds bind metal ions to form complexes with structure (3) rather than structure (4), for which evidence has been claimed31 in one case only. 

Hydroxylamine, O-acetyl-N-benzoyl-N-phenyl-hydroxamic acids from, 506 Hydroxylamine ligands, 101 Hydrozirconation, 342 Hypoxanthines metal complexes, 93... 

Raman spectroscopy metal in water complexes, 309 Rare earth complexes acetylacetone synthesis, 377 guanidinium, 282 hydroxamic acids, 506 Redox properties bipyridyl metal complexes, 90 Reductive coupling nitrile metal complexes, 265 Resorcinol, 2,4-dinitro-metal complexes, 273 Rhenium complexes acetylacetone, 376 synthesis, 375, 378... 

Valinomycin metal complexes, 969 Vanadium complexes acetylacetone exchange reactions, 380 1,4-diaza-l,3-butadiene, 209 dioxygen mononuclear, 321 hydrazido(2-), 148 hydroxamic adds, 506 phthalocyanines, 865 polypyrazolylborates, 248 porphyrins, 824 dioxygen adducts, 325... 

Gutsche et al. observed that a lipophilic dioxime (the ligand in 4) accelerates by a factor of 60 to 140 the hydrolysis of acetyl phosphate in the presence of an equimolar amount of metal (M = Cu, Zn, Ni) under comicellar conditions with cetyl trimethylammonium bromide (CTAB) at pH 11.5 [22], The hydrolysis reaction was followed by pseudo-first-order kinetics at [ligand] = [M] = 2.5 mM and [CTAB] = 250 mM. Although a possible complex 4 was proposed to exist in the hydroxamate form, there were no experimental data for the stability and structure of metal complexes at pH 11.5 (e.g., it is not known whether the... 

No substances containing only a single hydroxamic acid bond have thus far been isolated from natural materials as the metal complex. They are included here, however, in view of the known affinity of even monohydroxamic acids for iron (2) and also because some are related to higher hydroxamates for which a role in iron metabolism seems assured, l us-arinine, for instance, is both a constituent of ferrirhodin and is produced at high levels in iron deficiency. Although the structures are quite varied they are, for the most part -- like the di- and tri- hydroxamates — derived from the N-hydroxyamino acids. 

Dutta, R. L. Metal complexes of hydroxamic acids. Colored complexes of iron, vanadium and molybdenum with isonicotinohydroxamic acids and their analtyical uses. J. Ind. Chem. Soc. 36, 285 (1959). 

Chromic Ferrichrome Complexes. The spectra for the model chromic hydroxamate complexes are reproduced in Figure 6. Since the visible and CD spectra of the isomers are wholly dominated by the metal complex chromophore, these data can be used to characterize and to identify coordination isomers of complexes formed by the siderophores. The preparation and characterization of the chromic complexes of des-ferriferrichrome and desferriferrichrysin have been reported (3). Although an examination of molecular models for both complexes shows two coordination isomers are possible (A-cis and A-cis), both chromic complexes consist exclusively of the A-cis isomer. These results agree with x-ray crystallographic investigations which have shown that both ferri-chrysin and ferrichrome A crystallize as only the A-cis isomer (14, 15). Both chromic complexes have identical CD spectra which are the same as the A-cis Cr(men)3 spectrum (Figure 6). 

As with hydroxamate siderophores, simple tris(catecholato) metallate(lll) complexes have served as models for enterobactin. Unlike hydroxamate, catecholate is a symmetric, bidentate ligand. Consequently, there are no geometrical isomers of simple tris(catecholato) metal complexes, and only A and A optical isomers are possible. However all siderophore catecholates are substituted asymmetrically on the catechol ring, such that geometric isomers may in principle exist. However, in the case of enterobactin molecular models show only the more symmetric cis chelate is possible, as the A or A form. 

Formation constants of 3d metal ions with A-m-tolyl-p-substituted benzohydroxamic acids and of rare earths with thenoylhydroxamic acid have been determined. Formation constants of proton and metal complexes of iV-phenyl-2-thenoyl- and A-p-tolyl-2-thenoyl-hydroxamic acids have also been determined. In addition, study has been made of the mixed ligand complexes involving nicotine- and isonicotino-hydroxamic acids. A method of extraction and spectrophotometric determination of vanadium with chlorophenylmethylbenzohydroxamic acid has also been published. It may be mentioned that hydroxamic acids (in particular, the A-phenylbenzohydroxamic acid) have been widely used as analytical reagents for metal ions. Solvent extraction of titanium by benzo- or salicyl-hydroxamic acid in the presence of trioctylamine in the form of coloured complexes has been reported. A-w-Tolyl-p-methoxybenzohydroxamic acid has been used for extraction and spectrophotometric determination of Mo and W from hydrochloric acid media containing thiocyanate. 

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