Oxalate zinc complexes

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). 

Mixed oxalate-salicylate complexes of Cd of the stoicheiometry [Cd(oxXsal)] and [Cd(ox)(sal)2] have been detected stability constants for these, [Cd-(ox) ] " (n = 1—3), and [Cd(sal) ] "" (n = 1 or 2) have also been determined. ° In oxalate solution, Hg forms the mixed complexes [Hg(C204)X ]" ( = 1, X = SCN = 1 or 2 X = OAc, NO2, Br, or tartrate). The complexation of Cd by tartrate has also been investigated. Stability constants for mixed complex formation between piperidine and a variety of zinc and cadmium mono- and dicar boxylic acids have been reported. " ... 

It has been known for some time that tolerance towards high levels of both essential and toxic metals in a local soil environment is exhibited by species and clones of plants that colonize such sites. Tolerance is generally achieved by a combination of exclusion and poor uptake and translocation. Some species can accumulate large quantities of metals in their leaves and shoots at potentially toxic levels, but without any harmful effects. These metal-tolerant species have been used in attempts to reclaim and recolonize metal-contaminated wastelands. More recently such species have attracted the attention of inorganic chemists. There is abundant evidence that the high metal levels are associated with carboxylic acids, particularly with nickel-tolerant species such as Allysum bertolonii. The main carboxylic acids implicated are citric, mahc and malonic acids (see refs. 30 and 31 and literature cited therein). Complexation of zinc by malic and oxalic acids has been reported in the zinc-tolerant Agrostis tenuis and oxalic acid complexation of chromium in the chromium-accumulator species Leptospermum scoparium ... 

A fluorescent DAQZ 2Zn + complex, 13 was reported as a sensor in live cells for oxalic acid, presence of which resulted in quenching (Fig. 16). Additionally, a binuclear BODIPY-based fluorescent zinc complex was developed and investigated in cells by Hamachi et Histological studies demonstrated that the complex could distinguish neurofibrillary tangles of hyperphospohylated tau proteins and amyloid plaques in the hippocampus of a patient who had Alzheimer s disease. 

Calcium forms stable insoluble salt with oxalic acid (see Section 10.2.3.2). In plant cells with higher concentrations of oxalic add, caldum oxalate can be actually present in the form of crystals. Some plants have been shown to bind metals in mixed complexes. For example, chromium can be bound in an oxalate-malate complex, and nickel and zinc can form a dtrate malate complex. Citric add has been proven to be a low molecular weight zinc ligand in human milk, and in casein micelles it binds calcium. It is also used as a food additive (acidulant, synergist to antioxidants and sequestrant), so great attention has been paid to the formation of its complexes with metal ions. The addition to cereal products leads to increased solubihty of naturally present iron, due to its release from phytic acid salts (phytates). 

Sulphuric acid is not recommended, because sulphate ions have a certain tendency to form complexes with iron(III) ions. Silver, copper, nickel, cobalt, titanium, uranium, molybdenum, mercury (>lgL-1), zinc, cadmium, and bismuth interfere. Mercury(I) and tin(II) salts, if present, should be converted into the mercury(II) and tin(IV) salts, otherwise the colour is destroyed. Phosphates, arsenates, fluorides, oxalates, and tartrates interfere, since they form fairly stable complexes with iron(III) ions the influence of phosphates and arsenates is reduced by the presence of a comparatively high concentration of acid. 

C18-0033. Zinc oxalate, Zn(C2 O4), is sparingly soluble in water (Zjp = 1.4 X 10 ). The Zn ion forms a tetrahedral-shaped complex with ammonia. The formation constant for the complex is 4.1 X 10. How many moles of zinc oxalate will dissolve in 1.0Lof0.200M aqueous ammonia ... 

C18-0121. Zinc forms an octahedral complex ion with three bidentate oxalate ions ... 

A PRP -1 (Hamilton Reno, NV) reversed phase column was coated with cetylpyridinium and eluted with tetramethylammonium salicylate acetoni-trile water.89 The separation was comparable to that observed on conventional ion exchange. Coated phases were also used to separate oxalate complexes of manganese, cobalt, copper, and zinc.90 Reversed phase silica supports were coated with poly(N-ethyl-4-vinylpyridinium bromide), poly(dimethydiallylammonium chloride), poly(hexamethyleneguanidinium... 

An example of the above mentioned cascade complexation of carboxylates by macrocyclic receptors containing metal ionic centers is the inclusion of oxalate by the dien dicobalt complex 9 (Martell, Mitsokaitis) [12]. Similarly, the -cyclodextrin (jS-CD) 10, modified with a zinc cation bound by a triamine side chain, encapsulates anions like 1-adamantylcarboxylate in its cavity, fixing them by combined electrostatic and hydrophobic interactions [13], Zinc s group achieved the enantioselective transport of the potassium salts of N-protected amino acids and dipeptides by making use of the cation affinity of... 

When an electrolyte which is without action on vanadium at ordinary temperatures (for example, dilute solutions of mineral acids, of oxalic acid, or of potassium halides) is electrolysed with a vanadium anode, a complex tetravalent vanadium ion is produced. Similarly, electrolysis at 100° C. and in molten chlorides of sodium or zinc gives rise to complex tetravalent vanadium ions. The E.M.F. in each case is found to be independent of the nature of the electrolyte. When, however, solutions of caustic soda or of caustic potash are employed, the vanadium dissolves as a pentavalent ion, irrespective of variations... 

The properties of the complexes Zn[Cr04] and Zn[Cr04] 3.5Zn(OH)2 H20 have been investigated their reduction by CO (formed in situ from the decomposition of zinc oxalate) leads to the formation of species containing catalyticaliy active Crv and Cr111 centres.680,681... 

In our studies of the open-framework zinc oxalates, we have recently isolated monomeric, dimeric, ID linear chain, 2D layer, and 3D structures by the reaction of amine oxalates with Zn2+ ions,21 suggesting thereby that the presence of a hierarchy of structures is not unique to the phosphates alone. We believe that the evidence provided by our studies for the existence of an Aufbau principle of open-framework complex structures is of considerable significance. Many other complex inorganic structures are also likely to be formed by similar building-up processes, involving basic building units and self-assembly. 

Oxalic acid is capable of combining with minerals to form salt complexes. Calcium and zinc form the least soluble salts with oxalic acid (, ). Spinach contains more oxalic acid than most foods (approximately 700 mg/100 g), and its effect on calcium availability has been studied rather extensively. Other green leafy vegetables also contain considerable amounts of oxalic acid, and the oxalic acid is concentrated more in the leaves than in the stalks (7 ). Rhubarb, some nuts, tea, and cocoa have also been found to contain oxalic acid in amounts greater than 200 mg/100 g food (7-jJJ. 

Further investigation is needed on the combined effects of oxalic acid and fiber. In vitro studies could provide clues to the nature of the binding of minerals to oxalic acid and fiber whether oxalic acid and fiber each binds part of the zinc, or whether there is a fiber-zinc-oxalate complex formed. 

The metal ions are separated on an ion exchanger as oxalate or PDCA complexes (PDCA pyridine-2,6-dicarboxylic acid). They are then mixed with the PAR reagent and form chelate complexes which absorb in the wavelength range between 490 and 530 nm. A uniform response factor for the different metal ions is obtained by adding Zn-EDTA to the PAR reagent [21]. The metal ions in the column effluent dispel an equivalent zinc ion concentration from the Zn-EDTA complex, which then form the respective chelate... 

Gallium (Ga, at. mass 69.72) forms colourless Ga " ions. It occurs in solution exclusively in the III oxidation state. Gallium resembles aluminium and zinc in its properties. The hydroxide, Ga(OH)3, precipitates at pH 3, but dissolves in weakly alkaline media (pH 8-9). Gallium forms halide, oxalate, tartrate, acetate, and EDTA complexes. 

Gallium can be separated from Al and Zn on anion- or cation-exchange columns with the use of oxalate, tartrate, or EDTA complexes. In an ammonium carbonate medium, Ga exists as the anionic carbonate complex, whereas zinc exists as the cationic ammine complex. 

Niobium (Nb, at. mass 92.91) hydrolyses (in the absence of complexing anions) over the pH range 0-14. Polymerized forms of Nb(V) give pseudo-solutions or they separate as a white precipitate. When fused with NaOH, Nb20s forms the niobate, which is soluble in NaOH solutions. Niobium(V) forms stable fluoride, tartrate, oxalate, and peroxide complexes. The niobium complexes are more stable than the corresponding Ta complexes. A niobium chloride complex is formed in >5 M HCl solutions. Niobium(V) can be reduced to coloured species of Nb(III) and Nb(IV). In an acid medium, zinc metal reduces Nb(V), but not Ta(V). 

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