Chromium dichloride

Chromium (II) salts reduce water into hydrogen. This gradual transformation at ambient temperature has been responsible for accidents of the same nature. A glass bottle, in which chromium dichloride was stored for several years, detonated spontaneously. A sealed tube, in which there was chromium (II) sulphate heptahydrate and water in excess, detonated after being stored in darkness for a year. In both cases the accidents were interpreted as the result of water reduction, forming hydrogen whose pressure eventually caused the explosion of the containers. 

Once made, the chromium dichloride/diethyl ether mixture combusts immediately. 

Chemical deoxygenation of sulfoxides to sulfides was carried out by refluxing in aqueous-alcoholic solutions with stannous chloride (yields 62-93%) [186 Procedure 36, p. 214), with titanium trichloride (yields 68-91%) [203], by treatment at room temperature with molybdenum trichloride (prepared by reduction of molybdenyl chloride M0OCI3 with zinc dust in tetrahydrofuran) (yields 78-91%) [216], by heating with vanadium dichloride in aqueous tetrahydrofuran at 100° (yields 74-88%) [216], and by refluxing in aqueous methanol with chromium dichloride (yield 24%) [190], A very impressive method is the conversion of dialkyl and diaryl sulfoxides to sulfides by treatment in acetone solutions for a few minutes with 2.4 equivalents of sodium iodide and 1.2-2.6 equivalents of trifluoroacetic anhydride (isolated yields 90-98%) [655]. 

Preparation of (2-methyl-3-phenyl-l-(8-quinolyl)cyclopentadienyl) chromium dichloride... 

Aldehydes, RCHO, have been reductively olefinated (to /ran -RCH=CHR) using chromium dichloride and trichlorosilane, apparently via a novel chromium Brook rearrangement.189 In one case, a trans- 1,2-diol (a putative intermediate in such a mechanism) was isolated. 

Emrich et al.42 have reported the preparation of a chromacyclopentane in high yield (70-90%), using two different methods. The chromacyclopentane 37 can be synthesised by the reaction of the appropriate chromium dichloride with (i) 1,4-dilithiobutane or (ii) active Mg in the presence of ethene [Eq. (16)] (Fig. 11). 

Diaryliodonium salts 98 react with aldehydes 99 in the presence of chromium dichloride and nickel dichloride with the formation of benzyl alcohols 100 (Scheme 44) [74]. The mechanism of this reaction involves the generation of organochromium(III) species via reaction of iodonium salts with chromium dichloride, followed by their nucleophilic addition to aldehydes to yield alcohols. 

There seems to be even less structural similarity for many other metal halides as the crystalline systems are compared with the molecules in the vapor phase. Aluminum trichloride, e.g., crystallizes in a hexagonal layer structure. Upon melting, and then, upon evaporation at relatively low temperatures, dimeric molecules are formed. At higher temperatures they dissociate into monomers (Figure 9-58) [107], The coordination number decreases from 6 to 4 and then to 3 in this process. However, at closer scrutiny, even the dimeric aluminum trichloride molecules can be derived from the crystal structure. Figure 9-59 shows another representation of crystalline aluminum trichloride which facilitates the identification of the dimeric units. A further example is chromium dichloride illustrated in Figure 9-60. The small oligomers in its vapor have structures [108] that are closely related to the solid structure [109], Correlation between the molecular composition of the vapor and their source crystal has been established for some metal halides [110],... 

Figure 9-60. Four-membered rings are present both in (a) The crystal and (b) The vapor-phase molecules of chromium dichloride [112],...

A variation of this reaction was developed in 1986 by Takai and Utimoto, in which geminal dihaloalkanes were added to aldehydes in a reaction mediated by chromium dichloride. This led to the stereoselective formation of the corresponding tran5-olefins 10 [12]. The major drawback of this method is the rather cumbersome access to the corresponding substituted dihalomethane compounds, which prevents a broad application of this reaction for synthesis. 

These are listed in Table 17-C-2. The anhydrous Cr11 halides are obtained by action of HF, HC1, HBr, or I2 on the metal at 600 to 700°C or by reduction of the trihalides with H2 at 500 to 600°C. Chromium dichloride is the most common and most important of these halides, dissolving in oxygen-free water to give a blue solution of Cr2+ ion. 

SYNS CHLORURE de CHROMYLE (FRENCH) CHROMIC OXYCHLORIDE CHROMIUM CHLORIDE OXIDE CHROMIUM DICHLORIDE DIOXIDE CHROMIUM DIOXIDE DICHLORIDE CHROMIUM(VI) DIOXYCHLORIDE CHROMIUM OXYCHLORIDE CHROMOXYCHLORID (GERMAN) CHROMYLCHLOR-ID (GERMAN) CHROOMOXYLCHLORIDE (DUTCH) CROMILE, CLORURO di (ITALIAN) CROMO, OSSICLO-RURO di (ITALIAN) DICHLORODIOXOCHROMIUM DIOXODICHLOROCHROMIUM OXYCHLORURE CHROMIQUE (FRENCH)... 

CHROMIUM DICHLORIDE (10049-05-5) Very hygroscopic. Stable in dry air but oxidizes rapidly when moist. Oxidized in water to trivalent chromium and chloride ions, with liberation of explosive hydrogen. Sealed containers have been reported to explode from pressure of hydrogen. The aqueous solution is an acid and incompatible with sulfuric acid, alkalis, ammonia, aliphatic amines, alkanolamines, alkylene oxides, amides, epichlorohydrin, organic anhydrides, isocyanates, nitromethane, vinyl acetate. 

CHROMIUM DICHLORIDE DIOXIDE (14977-61-8) A powerful oxidizer. Violent reaction with water, producing hydrochloric and chromic acids, and chlorine gas. Potentially violent and explosive reaction with reducing agents, acetone, alcohols, calcium sulfide, combustible materials, gaseous or liquid ammonia, ethers, nonmetal halides, fuels, nonmetal hydrides, fluorine, organic matter, organic solvents, phosphorus, phosphorus trichloride, sodium azide, elemental sulfur, sulfur monochloride, turpentine, urea. Decomposes slowly in light. 

CoCI3[g] COBALT TRICHLORIDE (GAS) 538 Cr02CI2[g] CHROMIUM DICHLORIDE DIOXIDE (GAS) 574... 

Synonyms/Trade Names Chlorochromic anhydride. Chromic oxychloride. Chromium chloride oxide. Chromium dichloride dioxide. Chromium dioxide dichloride. Chromium dioxychloride. Chromium oxychloride. Dichlorodioxochromium... 

CAS 10049-05-5 EINECS/ELINCS 233-163-3 Synonyms Chromium chloride Chromium (II) chloride Chromium (II) chloride (1 2) Chromium (II) chloride anhydrous Chromium dichloride Chromous chloride Empihcai Cl2Cr Formuia CrCl2... 

---