Hydroxamic acids metal complexes

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). 

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). 

The development of transition metal mediated asymmetric epoxidation started from the dioxomolybdcnum-/V-cthylcphcdrinc complex,4 progressed to a peroxomolybdenum complex,5 then vanadium complexes substituted with various hydroxamic acid ligands,6 and the most successful procedure may now prove to be the tetroisopropoxyltitanium-tartrate-mediated asymmetric epoxidation of allylic alcohols. 

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. ... 

Complexation of metal ions by hydroxamic acids is the starting point of a number of analytical determinations . All hydroxamic acids, in acid solutions, react with ferric chloride to give rust brown complex salts 89 (Scheme 47). These colored complexes form the basis for the sensitive qualitative and quantitative determination of carboxylic acids and their derivatives too. 

For hydroxamic acids, it is generally assumed that it is the Af-hydroxyamide/keto form, as opposed to the hydroximic/hydroxyoxime form, that predominates in acid medium, the environment usually required for most precipitates or colors to form . It is in general unknown what is the stoichiometry and structure of most metal hydroxamate complexes in solution. Nevertheless, the reaction of the majority of hydroxamic acids with metal ions can be written schematically as shown in equation 2. 

Our review on the use of oximes and hydroxamic acids in inorganic analytical chemistry showed that these reagents are/were most frequently used for gravimetric determinations, determinations based on complexation, spectrophotometric determinations and separations, while their use for column separations, as electrode sensors, as supporting electrolytes or compounds that enhance sensitivity of determination is less common. Additionally, it was noticed that the analytical chemistry of anions is less advanced than that of cations and for this reason this chapter was limited to analytical chemistry of metallic cations. 

Ortho-directed metallations also allowed the synthesis of ferrocene-based hydroxamic acids such as 17 and 18 [23] as well as the preparation of planar-chiral carbenes 19 and 21 (which were trapped as chromium and rhodium complexes, 20 and 22, respectively) [24], In this context it is noteworthy that 19 was the first carbene with planar chirality ever reported. 

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. 

A large volume of work64 has been published on the determination of stability constants for complexes of hydroxamic acids, e.g. acetohydroxamic acid.65 The stability of 3d transition metal ions (Mn2+ to Zn2+) with salicylhydroxamic and 5-methyl-, 5-chloro-, 5-bromo-, 5-nitro-, 4-chloro-, 4-bromo- and 3-chloro-salicylhydroxamic acids,66 as well as with methyltolylbenzohydroxamic acid,67 has been studied potentiometrically. Stability constants of iron(III) with a number of hydroxamic acids have been determined by redox potential studies.68... 

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... 

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... 

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