Chromium II acetate

The anhydrous hahdes, chromium (II) fluoride [10049-10-2], chromium (II) bromide [10049-25-9], CrBr2, chromium (II) chloride [10049-05-5], CrCl2, and chromium (II) iodide [13478-28-9], 03x1, are prepared by reaction of the hydrohaUde and pure Cr metal at high temperatures, or anhydrous chromium (II) acetate [15020-15-2], Cr2(CH2COO)4, atlower temperatures, or by hydrogen reduction of the Cr(III) hahde at about 500—800°C (2,12). 

Chromium(III) acetate, 6 533 Chromium(II) acetate dihydrate, physical properties, 6 528t... 

Bis(acrylonitrile)nickel(0), 2312 l,2-Bis(dichlorophosphino)ethane, 0797 Bis(trimethylsilyl) phosphonite, 2611 Bromodimethylborane, 0887 Calcium silicide, 3943 Cerium trisulfide, 3967 Chromium(II) acetate, 1493 Chromium(II) oxide, 4241 Cobalt(III) nitride, 4214 Cobalt(II) sulfide, 4218 Dicobalt boride, 0128 Dimethyl ethanephosphonite, 1732 Europium(II) sulfide, 4293 2-Furaldehyde, 1836 Indium(II) oxide, 4641... 

Preparation of Chromium(II) Acetate. Assemble an apparatus as shown in Fig. 126. Fill wash bottles 2 and 3 with an alkaline solution of pyrogallol, and columns 4, 5, and 6 with solid granulated sodium hydroxide. 

Transfer the dry chromium(II) acetate into a drawn out test tube and seal it (wear eye protection ). Weigh the ampoule with the substance and the remaining part of the tube, and calculate the yield in per cent. 

Dehalogenation. Barton et at. (1, 148) effected dehalogenation of steroidal /i-hydroxy halides with chromium(II) acetate and butancthiol as the proton donor in DMSO. The method is only useful with tertiary halides. A recent improvement that permits reduction of halides of all types uses the ethylenediamine complex of CrtCIOzh and the tetrahydropyranyl ethers of the /J-hydroxy halide. Catalytic amounts of the reducing agent can be used in "indirect electrolysis." The reaction is convenient for preparation of deoxynucleosides.1... 

Attempts to isolate pure cyanochromium(II) complexes from the deep red solutions containing [Cr(CN)6]4 ions formed when chromium(II) acetate is added to aqueous potassium cyanide in excess, and in other ways, have not been very successful. Now, through careful control of concentration and of pH, the known but poorly characterized green crystalline hexacyanochromates(II) M4[Cr(CN)6]-2H20 (where M = Na or K), the new dark green simple cyanide Cr(CN)2-2H20, and their anhydrous forms have been prepared pure (Scheme 1 and Table 2).10... 

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. 

Chromium(II) acetate monohydrate, discovered by Peligot in 1844, is the best known chromium(II) compound because it can be precipitated readily from aqueous Cr11 solutions by sodium acetate, is stable in air for short periods, and is used as a reducing agent and a source of other chromium(II) compounds (Table 9). Nonetheless, in its deep red colour, feeble paramagnetism and acetate-bridged, binuclear structure (24) (determined in 1953 and refined in 1971),154155 which are still not completely understood, it differs sharply from other chromium(II) salts (Section 35.3.5.1). 

The pentaacetatodiborate Cr[B20(0C0Me)5]2 has been prepared (p2 3K = 4.80 BM).209 Chromium(II) acetate is predominantly dimeric in water in which it is not very soluble. The equilibria are shown below. 

Trifluorochromates, ACrF3 (A = NH4, K or Rb), can be prepared in aqueous conditions from chromium(II) chloride and AF or chromium(II) acetate and AHF2.224,236 The potassium salt has also been prepared by fusing CrF2 with KF under argon.237... 

Cyclization of an allyl A-acyl-1 -phenylglycinate (398) with triphenylphosphine, hexa-chloroethane and triethylamine affords a 2-allyl-3-oxazolin-4-one (400) (81AG(E)395, 77AG(E)394). Reductive cleavage of the oxazolinone with chromium(II) acetate and aqueous hypophosphorous acid furnishes a j3,y-unsaturated ketone (Scheme 88). 

The slurry is filtered under an inert atmosphere, in an apparatus similar to that described for chromium (II) acetate (No, 35), washed three or four times with 50ml of absolute alcohol, and then with two similar portions of absolute ether. During the filtration and washings the same precautions are observed as for the chromium salt. The material is dried in a desciccator filled with an melt gas and stored in tightly stoppered bottles under an indifferent atmosphere. 

A one-liter Erlenmeyer flask is substituted in the apparatus for reduction described in Experiment No. 35. The flask is charged with 145g of chromium (III) chloride 6-hydrate dissolved in a mixture of 150ml of concentrated hydrochloric acid and an equal volume of water. Fifty-five grams of zinc (coarsely granulated or in the form of rods) is added and the reduction procedure is then followed exactly as for chromium (II) acetate. 

CrXi, which dissolve in water with the evolution of heal, although the fluoride is less soluble than the other halides. The ammoniacal solution of chromium(II) sulfate, CrS04, is particularly reactive with gases, not only with oxygen like the other Cr compounds, but also acetylene. Chromium(II) acetate is only slightly soluble in HiO... 

Cotton and Mott3 reported the reaction of chromium(II) acetate with Me2NCH2CH2ONa to form an unusual tetrameric product in which each V,lV-dimethylaminoethanolate group is N—O bidentate but bridges through O to other Cr atoms in the tetramer. A recent protonation and aquation study on Crni/ethanolamine complexes4 has shown a sequence of reactions involving initial... 

Chromic acid, 4223 Chromium, 4216 Chromium(II) acetate, 1489 Chromium(II) chloride, 4046 Chromium(III) chloride, 4121 Chromium(III) oxide, 4245... 

The mixture is suction filtered, the precipitate being collected on a tared, Pyrex-glass filtering crucible of medium porosity. The product is next washed several times with small portions of water until the washings are free of chloride ion, as tested with silver nitrate solution. Finally, it is washed with a little ethanol followed by a little ether. The crucible containing the product is placed in a vacuum desiccator over concentrated sulfuric acid and dried for 1 day with occasional addition of nitrogen to the desiccator, followed by reevacuation. The yield of chromium(II) acetate is 6.1 g. (95% of theory). 

The chromium(II) acetate thus obtained can be converted into other chromium(II) salts by observing the same conditions as those for the above synthesis. This general method finds wide application in the preparation and handling of compounds which are easily oxidized, reduced, or hydrolyzed. 

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