Vanadium-carboxylates

Difference in vulcanizate tensile strength of EPDMs prepared with various catalyst systems, especially the high strength of EPDM prepared with vanadium carboxylates (V g)>is examined against various structural parameters. Effect of L r l ... 

Ethylene-propylene-diene terpolymers (EPDM), with their inherent complexity in structural parameters, owe their tensile properties to specific structures dictated by polymerization conditions, among which the controlling factor is the catalyst used in preparing the polymers. However, no detailed studies on correlation between tensile properties and EPDM structures have been published (l,2). An unusual vulcanization behavior of EPDMs prepared with vanadium carboxylates (typified by Vr g, carboxylate of mixed acids of Ccj-Cq) has been recently reported Q). This EPDM attains target tensile properties in 18 and 12 minutes at vulcanization temperatures of 150 and l60°C respectively, while for EPDMs prepared with V0Cl -Et3Al2Cl or V(acac) -Et2AlCl, about 50 and 0 minutes are usually required at the respective vulcanization temperatures, all with dieyclopentadiene (DCPD) as the third monomer and with the same vulcanization recipe. This observation prompted us to inquire into the inherent structural factors... 

The tert-huty hydroperoxide is then mixed with a catalyst solution to react with propylene. Some TBHP decomposes to TBA during this process step. The catalyst is typically an organometaHic that is soluble in the reaction mixture. The metal can be tungsten, vanadium, or molybdenum. Molybdenum complexes with naphthenates or carboxylates provide the best combination of selectivity and reactivity. Catalyst concentrations of 200—500 ppm in a solution of 55% TBHP and 45% TBA are typically used when water content is less than 0.5 wt %. The homogeneous metal catalyst must be removed from solution for disposal or recycle (137,157). Although heterogeneous catalysts can be employed, elution of some of the metal, particularly molybdenum, from the support surface occurs (158). References 159 and 160 discuss possible mechanisms for the catalytic epoxidation of olefins by hydroperoxides. 

Many metals occur in crude oils. Some of the more abundant are sodium, calcium, magnesium, aluminium, iron, vanadium, and nickel. They are present either as inorganic salts, such as sodium and magnesium chlorides, or in the form of organometallic compounds, such as those of nickel and vanadium (as in porphyrins). Calcium and magnesium can form salts or soaps with carboxylic acids. These compounds act as emulsifiers, and their presence is undesirable. 

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... 

Oxidation of Aldonic Acids. Preferential oxidation of the secondary alcoholic group adjacent to the carboxyl group in sugar acids or aldonic acids such as L-gulonic acid (XXV) can be carried out with chromic acid12 or with chlorates in the presence of a vanadium catalyst.13... 

Another interesting asymmetric epoxidation technique using metal catalysis involves the vanadium complexes of A-hydroxy-[2.2]paracyclophane-4-carboxylic amides (e.g., 19), which serve as catalysts for the epoxidation of allylic alcohols with f-butyl hydroperoxide as... 

Unisulf [Unocal sulfur removal] A process for removing sulfur compounds from petroleum fractions, similar to the Stretford process, but including in the catalytic solution vanadium, a thiocyanate, a carboxylate (usually citrate), and an aromatic sulfonate complexing agent. Developed by the Union Oil Company of California in 1979, commercialized in 1985, and operated in three commercial plants in 1989. 

The thermally induced carboxylation of alkanes has been thoroughly investigated by the same group, who have developed a range catalysts, based on vanadium (VO(acac)2) or palladium analogs.22,22a,22b Photochemically induced carbonylation of linear alkanes, to afford aldehydes, is also known (Equation (15)).23,23a... 

The hydroquinone process was developed by BASF [12]. Hydroquinone-2,5-di-carboxylic acid is prepared by a modified Kolbe-Schmidt synthesis from hydroquinone and carbon dioxide. Subsequent reaction with arylamine in an aqueous-methanolic suspension in the presence of an aqueous sodium chlorate solution and a vanadium salt affords the product in good yield ... 

Shul pin and coworkers have demonstrated, in several papers, that other peroxo vanadium complexes closely related to 36, containing in the coordination sphere amino acids, nitrogen-containing bases or weak carboxylic acids, are effective oxidants of satnrated and aromatic hydrocarbons. An accnrate account containing this work, together with results related to the use of other transition metals, has appeared and aU the relevant literature can be found there. 

The reduction of carboxylatopentamminecobalt(III) complexes by vanadium(II) is predominantly inner-sphere.163 From [Co(en)(C204)2]- and [CofQO ]3-, (0204) and V3+ ions are primary products.164 tor N-bonded glycinato- and /3-alaninato-penta-amminecobalt(III), there is an intermediate with V11 attached to the unprotonated carboxylate group.165... 

In [V0(pmida)(H20)]-2H20 (pmida = /V-(2-pyridylmethyl)iminodiacetic acid), vanadium deviates by 0.39 A from the equatorial plane of two cts carboxylate oxygens, a water molecule and the pyridine nitrogen (see Figure 33b).811... 

Planar M30 units occur in the basic carboxylates of such metals as iron, ruthenium, manganese, vanadium and chromium the chromium compound has been known since 1919. The metal atoms are also linked by pairs of carboxylate ligands (often acetates), and have terminal ligands (generally pyridine or water). Mixed metal units, e.g. Fe2CrO,124 and mixed oxidation states, e.g. Ci CifO,1 ... 

A TS-1 that contains vanadium has been reported to be a highly active catalyst for the ozonization of 3,6-dichloropyridine-2-carboxylic acid. V-Silica-lite has lower activity, and V-Al-silicalite is inactive (Komatowski et al., 1993). 

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