Oxalates complexes with

Hislop and Bolton (1999) elucidated the complex mechanism of this reduction process. Presumably, it includes a ligand to metal electron transfer in the iron-oxalate complex with formation of an oxalyl radical anion as shown in Eq. 5-13. 

Infrared and UV/vis data have been used by several authors to identify the C=C, C=0, and M—O stretches in the complexes synthesized 15, 18-21, 37, 38, 41, 44, 50, 54, 56, 58, 59, 64-66, 69, 74, 78, 80, 82, 103). Except in the initial research on first-row transition metal complexes of squaric acid, where these data were used in proposing structures, IR and UV/vis analysis have been used as supporting evidence for the particular coordination mode of the ligand 19,21,22, 45, 52, 59, 65). Infrared spectroscopy has also been utilized in the study of mixed oxalate/squarate complexes 118), although not to the same extent as in complexes of the oxalate ion. For example, Scott et al. studied the IR properties of Co(III) oxalate complexes with the hgand in a variety of chelating/bridging situations 119). 

The actinides have a high degree of specificity for neutral and anionic oxygen-containing organic molecules. The actinide complexes with O -donor ligands that are most widely studied include alkoxides, aryloxides amide, carboxylates, and oxalates. Complexes with alcohols, ethers, esters, ketones, aldehydes, ketoenolates, and carbamates have also been reported. 

The oxalate complex K3[ri(C204)3(H20)] was prepared by the addition of excess K2[C204] to a solution of [Ti ((112N)2CO)6]Cl 3. The crystal structure revealed a seven-coordinate pentagonal bipyramidal geometry about the Ti center.989 The kinetics of electron transfer reactions between Ti oxalate complexes with Ru and Co complexes have been studied in detail.969,990,991... 

Tait CD, Janecky DR, Clark DL, Bennett PC (1991) Oxalate complexation with aluminum(III) and iron(III) at moderately elevated temperatures. In Kharaka Y K, Maest A S (eds) Water-rock interaction. Balkema, Rotterdam, pp 349-353 Tan KH (1980) The release of silicon, aluminum, and potassium during decomposition of soil minerals by humic acid. Soil Sci 129 5-11 Tandura SN, Voronkov MG, Alekseev NV (1986) Molecular and electronic structure of penta- and hexacoordinate silicon compounds. Top Curr Chem 131 99-189 Thurman EM (1979) Organic geochemistry of natural waters. Nijhoff, Dordrecht, 497 pp Webley DM, Henderson MEF, Taylor EF (1963) The microbiology of rocks and weathered stones. J Soil Sci 14 102-112... 

The aim of the present chapter is to look at the structures of transition-metal-oxalate complexes with nucleobases as a valuable source of information on molecular recognition patterns controlling the formation of these systems. Therefore, we focus our attention not only on the metal-nucleobase binding modes but also on the intramolecular interligand interactions, which cooperate with the coordination bond in the stabilization of the resulting mixed-ligand complexes. 

Depending upon the uranyl-oxalate ratio (1 1, 1 1.5, 1 2 or 1 3) complexes of the type UO2C2O4, [(U02)(C204)2] , or [(U02)(C204)3]" are formed. The uranyl oxalate complexes with C204 mol ratios... 

Coordination Complexes. The abiUty of the various oxidation states of Pu to form complex ions with simple hard ligands, such as oxygen, is, in order of decreasing stabiUty, Pu + > PuO " > Pu + > PuO Thus, Pu(Ill) forms relatively weak complexes with fluoride, chloride, nitrate, and sulfate (105), and stronger complexes with oxygen ligands (Lewis-base donors) such as carbonate, oxalate, and polycarboxylates, eg, citrate, and ethylenediaminetetraacetic acid (106). The complexation behavior of Pu(Ill) is quite similar to that of the light lanthanide(Ill) ions, particularly to Nd(Ill)... 

Carboxylates, Oxalates, and Catecholates. Complexes of Th(IV) with mono-, di-, tri-, and polycarboxylates have been extensively studied. Monocarboxylates, RCOO , have been complexed with Th(IV), eg, Th(RCOO)4, where R = H, CH, CCl, or and M Th(HC02)4, ... 

Ethylenediamine tetraacetic acid (EDTA) [60-00-4] (Sequestrene), an anticoagulent at 1 mg of the disodium salt per mL blood, complexes with and removes calcium, Ca ", from the blood. Oxalate, citrate, and fluoride ions form insoluble salts with Ca " and chelate calcium from the blood. Salts containing these anticoagulants include lithium oxalate [553-91-3] 1 mg/mL blood sodium oxalate [62-76-0]2 mg/mL blood ... 

In addition to the oxide carboxylates, beryllium forms numerous chelating and bridged complexes with ligands such as the oxalate ion C204 , alkoxides, /9-diketonates and 1,3-diketonates. These almost invariably feature 4-coordinate Be... 

Ruthenium, iridium and osmium Baths based on the complex anion (NRu2Clg(H20)2) are best for ruthenium electrodeposition. Being strongly acid, however, they attack the Ni-Fe or Co-Fe-V alloys used in reed switches. Reacting the complex with oxalic acid gives a solution from which ruthenium can be deposited at neutral pH. To maintain stability, it is necessary to operate the bath with an ion-selective membrane between the electrodes . 

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. 

Fig. 13. Possible structures for (acyloxy)boranes formed from the reaction of 9-BBN with oxalic acid and solid state structure of the complex with 2,2-dimethylmalonic acid 30...

In aq soln HgjfNOjfj reacts with Na4P207 (Na4L) to form complex ions with the formulas [Hg2(OH)L] and [Hg2L2r. The tripolyphosphate [PjO,)] " and tetrapolyphosphate [P40 3] ions form similar complex ions. The stability of these complex phosphates decreases as the chain length increases. The dicarboxylic acids oxalic, dimethylmalonic and succinic, H2L, form complexes with Hg2 ions ... 

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 ... 

Aluminium toxicity is a major stress factor in many acidic soils. At soil pH levels below 5.0, intense solubilization of mononuclear A1 species strongly limits root growth by multiple cytotoxic effects mainly on root meristems (240,241). There is increasing evidence that A1 complexation with carboxylates released in apical root zones in response to elevated external Al concentration is a widespread mechanism for Al exclusion in many plant species (Fig. 10). Formation of stable Al complexes occurs with citrate, oxalate, tartarate, and—to a lesser extent— also with malate (86,242,243). The Al carboxylate complexes are less toxic than free ionic Al species (244) and are not taken up by plant roots (240). This explains the well-documented alleviatory effects on root growth in many plant species by carboxylate applications (citric, oxalic, and tartaric acids) to the culture media in presence of toxic Al concentrations (8,244,245) Citrate, malate and oxalate are the carboxylate anions reported so far to be released from Al-stressed plant roots (Fig. 10), and Al resistance of species and cultivars seems to be related to the amount of exuded carboxylates (246,247) but also to the ability to maintain the release of carboxylates over extended periods (248). In contrast to P deficiency-induced carboxylate exudation, which usually increases after several days or weeks of the stress treatment (72,113), exudation of carboxylates in response to Al toxicity is a fast reaction occurring within minutes to several hours... 

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... 

As to the choice of anticoagulant, citrate is preferred to oxalate, because factor V is more stable in citrate than in oxalate. In addition, citrate rapidly complexes with calcium, forming a soluble complex, in contrast to the slow formation of the insoluble complex of calcium with oxalate (100). 

The NH2 radical rapidly reacts with excess oxalic acid required to form the oxalate complexes of titanium. 

The reaction of platinum(IV) complexes with ascorbate results in very slow reduction and for [PtCl2(OH)2(A ,A -dmen)], in the formation of the oxalate complex [Pt(C204)Cl(0H)(A , A-dmen)].508... 

Silver(I) complexes with mixed donor S, 0-ligands have been described with 1-hydroxypyridine-2-thione (261),1437,1438 cyclo-L-methionylglycine,1439 acyclic polyethers (262),1440-1442 dithio- and trithio-oxalate,1443 or chlorosulfate.1444... 

The aromatic spacer group of the model receptors prevent the formation of intramolecular hydrogen bonds between the opposing carboxyls yet these functions are ideally positioned for intermolecular hydrogen bonds of the sort indicated in 32. The acridine derivatives do indeed form stoichiometric complexes with oxalic, malonic (and C-substituted malonic acids) as well as maleic and phthalic acids, Fumaric, succinic or glutaric acids did not form such complexes. Though protonation appears to be a necessary element in the recognition of these diacids, the receptor has more to... 

Despite the volume of work concerned with metal-catalyzed decomposition of diazo compounds and carbenoid reactions 28>, relatively little work has been reported on the metal-catalyzed decomposition of sulphonyl azides. Some metal-aryl nitrene complexes have recently been isolated 29 31>. Nitro compounds have also been reduced to nitrene metal complexes with transition metal oxalates 32K... 

Several Pd11 complexes with thiolate or thioether derivative ligands have been studied to be applied in the hydroxycarbonylation reaction.394 Aminothiolate complexes of palladium with PPh3 catalyze the conversion of styrene to 2-phenylpropionic acid in high yield and excellent regioselectivity.644 Under mild conditions and in the presence of a catalytic amount of an S, TV-chelated palladium or//zo-amino-arenethiolate complex, styrene reacts with CO and oxalic acid or water to selectively give 2-phenylpropanic aid in high yield.645... 

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