Zinc carboxylates

For increased solubiHty to prevent bloom, shorter-chain carboxyHc acids or zinc carboxylates can be substituted. The use of chain-branched carboxyHc acids reduces the tendency for the formulations to lose sulfur cross-links or revert upon prolonged heating (7). Translucent articles such as crepe soles can use a zinc carboxylate or employ zinc carbonate as a transparent zinc oxide. 

Reaction between aldehydes or ketones and zinc carboxylates... 

Figure 4.1 Representation of the structure of MOF-5 (a) six carboxylic acid groups from terephthalic acid are connected to four Zn" cations to form a metal-organic elementary zinc carboxylate cluster (only...

Sanders (83) constructed a supramolecular assembly of heterometal-lic porphyrins held together by different types of metal-ligand interaction. The team exploited the different kinetic and thermodynamic properties of the pyridine-zinc, carboxylate-tin, and pyridine-... 

Dimeric zinc carboxylates do not have a large number of structurally characterized examples.362,363 Quite a number of monomeric carboxylate and particularly salicylate complexes have been structurally characterized.364"367... 

A polymeric chain structure is frequently observed for zinc carboxylates. Basic zinc carboxylates form a common tetrameric species, and altering conditions can result in an interconversion between the basic and regular carboxylates.369 Mass spectrometry studies have been carried out... 

The basic zinc carboxylate structure with a Zn40 core is now well characterized structurally with a number of examples.371 It can also form part of higher nuclearity structures and coordination networks.372,373... 

Trinuclear zinc carboxylate structures of the form MZn2(MeCH=CHC02)6(quinoline)2 have been structurally characterized with M = Mn, Co, Ni, Zn, Cd, Mg, Ca, Sr. Structural variation is observed for the group 2 metals. The remaining complexes all show linear trimers with the central metal atom octahedrally coordinated and linked to each zinc by two bidentate and one mono-dentate carboxylate.377 A basic benzoate octanuclear structure with four vanadium(III) and four zinc atoms has been characterized, [VZnO(benzoate)3(TF[F)]4-2TnF.378... 

Zinc carboxylate interactions have been exploited as part of a fluorescent molecular sensor for uronic acids. The sensors feature two interactions coordination of the carboxylate to the zinc and a boronic acid diol interaction.389 Photoluminescent coordination polymers from hydrothermal syntheses containing Zn40 or Zn4(OH)2 cores with isophthalate or fumarate and 4,4 -bipyridine form two- and three-dimensional structures. Single X-ray diffraction of both dicarboxylates identified the network structure.373... 

It has been proposed that the higher zinc carboxylates exhibit an enantiomeric polymorphism on the basis of the X-ray diffraction characteristics of the materials at elevated temperatures.778... 

Electrical conductivity studies on molten zinc carboxylates of even-numbered chain length from C6 to C18 are consistent with a small concentration of relatively mobile Zn2+ ions.779... 

A revitalization of interest in the copolymerization of epoxides and C02 can be traced to studies involving discrete zinc complexes. Several well-defined zinc monomeric and dimeric derivatives have been shown to be effective catalysts for the coupling of CHO and C02 to afford copolymers with high degrees of C02 incorporation. These include reports of sterically encumbering Ms-phenoxide derivatives of zinc [24], a highly fluorinated zinc carboxylate [25], and zinc [3-diiminate complexes [26] (see Figure 8.2). 

A suspension of zinc dust (1.0 g, 15.3 mmol) in 1-methylimidazole (lOmL, 126 mmol) was stirred for 48 hr under carbon dioxide atmosphere at 150°C in a 100-mL stainless steel autoclave a maximum value of 70 bar was noted for the pressure at 150°C. Over the course of the reaction, we obtained a clear, yellowish solution. The zinc reacted completely in this reaction. The 1-methylimidazole was distilled in vacuo (50°C at 0.1 bar) until a white precipitate formed. The white solid was vigorously stirred with diethyl ether. After filtration, the zinc carboxylate was dissolved in THF and layered with w-hexane. After a few days at room temperature, colorless prismatic crystals were collected. 

Concerning metal alkyl catalysts such as diethylzinc for the copolymerisation, it was established that they formed zinc carboxylate species owing to the reaction with maleic anhydride [192],... 

The tendency towards alternation in the oxirane/cyclic acid anhydride system with the zinc-based coordination catalyst is connected, according to literature data [193], with the stronger nucleophilic properties of the oxygen atom of the zinc alcoholate species and the weaker electrophilic properties of the zinc atom in such species compared with the respective properties of zinc carboxylate species. Studies of the copolymerisation of propylene oxide and maleic anhydride in the presence of catalysts such as diethylzinc-monoprotic compound (1 1) showed an increasing tendency towards alternation in systems with catalysts of decreasing electrophilicity of the zinc atom [186], which may corroborate the coordination mechanism proposed scheme (24). 

There are also basic zinc carboxylates having other types of structures, such as Zn5(0H)2(02CCHCHCH3)8, a chain polymer.14... 

Reformatsky-typc" reaction into zinc enolates (2) by treatment with zinc dust in a refluxing aromatic hydrocarbon solvent These undergo Oaisen rearrangement to zinc carboxylates (3) of y,d-unsaturated acids. Yields are depressed by a-alkyl substitution of (1) thus (3) is obtained in 100% yield when R = = CHj and R = R = H. 

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