Malonic acid metal complexes

Maleonitrile, l,2-dicyanoethylene-l,2-dithio-metal complexes, 6, 147 Malic acid metal complexes geochemistry, 6, 867 naturally occurring, 2,962 Malonic add... 

Beryllium, calcium, boron, and aluminum act in a similar manner. Malonic acid is made from monochloroacetic acid by reaction with potassium cyanide followed by hydrolysis. The acid and the intermediate cyanoacetic acid are used for the synthesis of polymethine dyes, synthetic caffeine, and for the manufacture of diethyl malonate, which is used in the synthesis of barbiturates. Most metals dissolve in aqueous potassium cyanide solutions in the presence of oxygen to form complex cyanides (see Coordination compounds). 

Simple organic molecules such as small carboxylic acids (oxalate, acetate, malonate, citrate, etc.), amino acids and phenols are all ligands for metals. Such compounds may all occur as degradation products of organic matter in natural waters. The complexes formed are typically charged hydrophilic complexes. The stability of the metal complexes with these ligands is, however, moderate in most cases. Model calculations including such compounds at realistic concentrations indicate that their effects on speciation are relatively small [29],... 

Many formation constants involve polycarboxylates Table 28 summarizes the data. Nagyp l and Fabian s report on the oxalic and malonic systems seems the most complete as hydrolysis of both metal ion and complexes has been included.584 A concentration distribution of the complexes in the malonic system is shown in Figure 25. The order of basicities is succinic > citraconic > itaconic > maleic > malonic acid and log /3U0 should follow the same order. However, from Table 28, the order of stabilities is citraconic > malonic > maleic > itaconic > succinic acid.608... 

Numerous versions of the Belousov-Zhabotinsky system differ by chemical compounds used. The typical reaction involves oxidation of some organic compound by bromate ion (BrOj ) occurring in acid medium with metal catalyst (Ce3+, Mn2+, as well as complexes of Fe2+, Ru2+). As an example, a particular reaction [4] could be mentioned, where an organic reductor is malonic acid CH2(COOH)2 and Ce3+ ions serve as a catalyst. In this reaction a solution changes periodically its colour due to oscillations in Ce3+ concentration. Generally speaking, the reaction consists of two stages. At the first one metal is oxidized... 

Humic substances, humic and fulvic acids, are essentially a mixture of compounds of different molecular weights. The total number of base-titratable groups is in the range of 10-20 meq per gram of carbon. Chelation by neighboring carboxyl and phenolic groups is the major mode of metal complexation. Compounds such as malonic acid, phthalic acid, salicylic acid, and catechol serve as convenient monomeric model compounds for estimating the coordi-native properties of humic substances. 

Bronsted LFERs also apply to reactions of metal ions (Lewis acids). Dissociation rates of Ni(II) complexes are correlated with corresponding dissociation equilibrium constants. This suggests that the reactions occur by dissociative interchange, in which breakage of the Ni(II)-ligand bond predominates over formation of the Ni(II)-water bond in the rate-determining step (Hoffmann, 1981). In addition, rates of metal-catalyzed decarboxylation of malonic acid are correlated with the stability constants for the metal-malonate complexes (Prue, 1952). 

Few data are available on the concentration of dicarboxylic acid anions in subsurface waters. C2 through C q saturated acid anions have been reported in addition to maleic acid (cz5-butenedioic acid) (5. 15-16L Oxalic acid (ethanedioic) and malonic acid (propanedioic) appear to be the most abundant. Reported concentrations range widely from 0 to 2540 mg/1 but mostly are less than a few 100 mg/1. Concentrations of these species in formation waters are probably limited by several factors, including the very low solubility of calcium oxalate and calcium malonate (5), and the susceptibility of these dicarboxylic acid anions to thermal decomposition (16). This paper will focus on the monocarboxylic acids because they are much more abundant and widespread, and stability constants for their complexes with metals are better known. We do recognize that dicarboxylic acid anions may be locally important, especially for complexing metals. 

Gagn6 et al. developed polymer active sites that additionally contained a receptor (recognition sites) displayed in the outer sphere of the metal center (reactive site). The Suzuki reaction of /)-bromoanisole with phenyl boronic acid and the allylation of dimethyl malonate with allyl acetate were both chosen to assess the presence and/or effect of the crown-ether in crown-ether-molecular imprinting polymer-palladium complex. The results showed that molecular imprinting can be used to functionalize the second-coordination sphere of a transition metal complex and subsequently affect its catalytic behavior. 

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 ... 

Noyes for bromate-malonic acid reaction and involves formation of BrOg radicals which oxidize the reduced metal complex. Silver(i) inhibition in the gallic acid reaction is observed, presumably by reduction of the Br present... 

Two accounts have been presented of the mechanisms of chemical oscillators. The cerium(iv)-catalysed oxidation of malonic acid by bromate serves as a model for a conceptual approach and in the second article other examples involving both homogeneous and heterogeneous processes are described. Two reviews have been published of radiation chemistry of metal ions in aqueous solution. - In one article, details are presented of reactions of main-group and first-, second-, and third-row transition metals and lanthanides and actinides. Meyerstein covers somewhat similar ground but deals with complexes in low, intermediate, and high oxidation states. The pulse radiolysis technique has recently been used to provide... 

The complexes formed by oxalic and malonic acids have been carefully studied and the detailed structural features have been obtained from X-ray diffraction measurements (Hansson, I973e). The oxalate ions in these complexes serve as bridging ligands and the larger metal ions have coordination number nine whereas the smaller ions have coordination number eight. The malonate ions in the rare earth malonates are of two different types, those that are involved in six-membered chelate ring formation and those which are not. 

In 1995, Shibasaki s group disclosed the first example of multifunctional heterobimetallic complex-catalyzed Michael reaction of malonate to enone. The chiral catalyst, lanthanum-sodium-BINOL complex (/ )-LSB, was prepared from La(Of-Pr)3, (/ )-BINOL, and NaOt-Bu. Two different metals indeed play their unique roles to enhance the reactivity of both substrate partners by locating them in designated positions. The Lewis acidic metal (lanthanides or group 13 elements) has been found capable to activate the acceptor, whereas the second metal center (alkali metals bound to a Brpnsted base) assists the coordination of enolate. The proposed catalytic cycle is shown in Scheme 9.5. 

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