Chromium , acetylacetonate complexes

Chromium complexes acetylacetone complex formation, 386 exchange reactions, 380 amidines, 276 bridging ligands, 198 chelating ligands, 203 carbamic add, 450 paddlewheel structure, 451 carboxylic adds, 438 trinuclear, 441 oorroles, 874... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Treatment of chromium (III) acetylacetonate with acetic anhydride and boron trifluoride etherate yielded a complex mixture of acetylated chelates but very little starting material. Fractional crystallization and chromatographic purification of this mixture afforded the triacetylated chromium chelate (XVI), which was also prepared from pure triacetylmethane by a nonaqueous chelation reaction (8, 11). The enolic triacetylmethane was prepared by treating acetylacetone with ketene. The sharp contrast between the chemical properties of the coordinated and uncoordinated ligand is illustrated by the fact that chromium acetylacetonate does not react with ketene. 

An alternative procedure starts from a metal complex of o-phenylenedi-amine. For example, the bis(o-phenylenediamine) complex of nickel(II) chloride reacts with acetylacetone to give a mixture of a nickel complex of the diamine and diketone together with 2,4-dimethylbenzodiazepinium chloride (76CPB1934 91JPR327). Chromium complexes have been used in the same way [91JCS(D)2045]. 

Tris(3-bromoacetylacetonato)chromium(III) is a dark red-brown crystalline material, which dissolves in benzene to form a green solution. The infrared spectrum of this chelate exhibits a characteristic strong singlet at 1540 cm. i, whereas chromium(III) acetylacetonate exhibits two peaks in this region, at 1560 and 1520 cm. b The ultraviolet spectrum of the brominated chromium chelate in chloroform exhibits a Xmax at 358 m/i(e = 13,070). The brominated chelate is reported to form a stable clathrate complex with chloroform (m.p. 240 to 241°). ... 

An alcoholic solution of [Cr(0H8)8](N03)3 is treated with the stoichiometric quantity of acetylacetone and then gently refluxed. The chromium complex crystallizes out after the excess alcohol Is distilled off. 

The decomposition of cyclohexylhydroperoxide was also studied in the presence of molybdenum and chromium complexes [356]. The decomposition of cyclohexylhydroperoxide in benzene catalyzed by [Mo02(acac)2], has many characteristics of the [VO(acac)2]-catalyzed reaction [355]. The ketone/alcohol ratio in the product was 1 and the kinetic pattern of reaction is similar. When chromium(III) acetylacetonate is used, however, there is a substantial difference. The chromium complex selectively converts cyclohexyl hydroperoxide to cyclohexanone. It is suggested that in this case the extent of release of free radicals to the solution is small [356]. The ketone/alcohol ratio in this case is " 13.7. The predominant formation of cyclohexanone on decomposition of cyclohexyl hydroperoxide in the presence of [Cr(acac)3] is no doubt related to the much higher yield of ketone obtained in cyclohexane oxidation in the presence of chromium complexes than observed when Mo or V compounds are used as catalysts [356]. 

This is by far the most stable and best-known oxidation state for chromium and is characterized by thousands of compounds, most of them prepared from aqueous solutions. By contrast, unless stabilized by M-M bonding, molybdenum(III) compounds are sparse and hardly any are known for tungsten(III). Thus Mo, but not W, has an aquo ion [Mo(H20)g] +, which gives rise to complexes [MoXg] " (X = F, Cl, Br, NCS). Direct action of acetylacetone on the hexachloromolybdate(III) ion produces the sublimable (Mo(acac)3] which, however, unlike its chromium analogue, is oxidized by air to Mo products. A black cyanide,... 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

Under the same conditions, cobalt acetylacetonate afforded a mixture of four products the mono-, di-, and triacetylated chelates (XVII, XVIII, and XIX), along with the starting material. In contrast to the chromium chelates, the mixture of cobalt complexes was cleanly separated by chromatography. The identity of each of these products was established by an NMR spectrum. The presence of uncoordinated carbonyl groups was revealed by infrared absorption at 1675 cm.-1... 

Complexes of acetylacetone (acacH), benzoylacetone (bzacH) and dipivaloylmethane (dpmH) have been reported. The acetylacetonate [Cr(acac)2] has been prepared from chromium(II) acetate and acetylacetone.142,143 It can also be obtained by the addition of aqueous sodium acetylacetonate to an aqueous solution of chromium(II) chloride, but in any preparation the yellow solid must be filtered off and dried as rapidly as possible, otherwise the chromium(III) compound is obtained. Its magnetic moment is 4.99 BM at room temperature consistent with a high-spin d4 configuration. 142The powerful reducing ability of [Cr(acac)2] has been used to prepare iron(II) and chromium(II) complexes80 of porphyrins and related ligands. 

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