Cadmium preparation

A donor such as hexamethylphosphoramide (HMPA) , dioxane or bipy , also can be added toward the end of the transmetallation to enable easier separation of the organometallic product from the metal halides present. This is particularly useful for organozinc and -cadmium preparations, because the reaction media cannot be treated with HjO to separate the metal halides, e.g., addition of HMPA to an EtjO solution containing an organocadmium product and Mg salts, MgXj, results in precipitation of MgX2 2 HMPA, thereby leaving R Cd in solution free of Mg halides, e.g. ... 

The reaction provides a valuable method of preparing anhydrous chlorides of metals. It has been used to prepare the anhydrous chlorides of copper(II), zinc, cadmium, chromium(III), iron(III). cobalt(Il) and nickel. 

Organocadmiura compounds may be prepared by the action of anhydrous cadmium chloride upon the corresponding Grignard reagents, for example ... 

Propiophenone. Prepare a solution of diphenyl-cadmium in 110 ml. of dry benzene using 4 9 g. of magnesium, 32 4 g. of bromobenzene and 19 5 g. of anhydrous cadmium chloride. Cool the solution to 10°, and add during 3 minutes a solution of 14 -8 g. of propionyl chloride (b.p. 78-79°) in 30 ml. of dry benzene use external coohng with an ice bath to prevent the temperature from rising above 40°. Stir the mixture for 2 hours at 25-35°. Work up the product as detailed above except that 6 per cent, sodium carbonate solution should replace the saturated sodium bicarbonate solution. The yield of propiophenone, b.p. 100-102°/16 mm., is 17 6 g. 

The superoxides are ionic soHds containing the superoxide, O - A comprehensive review of the superoxides was pubHshed ia 1963 (109) they are described ia Reference 1. Superoxides of all of the alkaU metals have been prepared. Alkaline-earth metals, cadmium, and 2iac all form superoxides, but these have been observed only ia mixtures with the corresponding peroxides (110). The tendency to form superoxides ia the alkaU metal series iacreases with increasing size of the metal ion. 

Organomineral peroxides of antimony arsenic, boron, magnesium, tin, cadmium, lead, silicon, and 2inc have been prepared by autoxidation and some are Hsted in Table 3 (33,44,60,93,115). For example, dimethyl cadmium reacts with oxygen to form methylperoxy methyl cadmium [69331-62-0] and bis(methylperoxy) cadmium. 

Cadmium Sulfide Photoconductor. CdS photoconductive films are prepared by both evaporation of bulk CdS and settHng of fine CdS powder from aqueous or organic suspension foUowed by sintering (60,61). The evaporated CdS is deposited to a thickness from 100 to 600 nm on ceramic substates. The evaporated films are polycrystaUine and are heated to 250°C in oxygen at low pressure to increase photosensitivity. Copper or silver may be diffused into the films to lower the resistivity and reduce contact rectification and noise. The copper acceptor energy level is within 0.1 eV of the valence band edge. Sulfide vacancies produce donor levels and cadmium vacancies produce deep acceptor levels. 

Other complex thiosulfates have been prepared to study crystal properties, eg, cadmium ammonium thiosulfates (90), NaAgS202 H2O [37954-66-8] (91), I C2Mg(S203)2 -6H20 [64153-76-0] (92), and (NH 2[Ag(S203)JCl2 [12040-89-0] (93). 

Titanium Dibromide. Titanium dibromide [13873-04-5] a black crystalline soHd, density 4310 kg/m, mp 1025°C, has a cadmium iodide-type stmcture and is readily oxidized to trivalent titanium by water. Spontaneously flammable in air (142), it can be prepared by direct synthesis from the elements, by reaction of the tetrabromide with titanium, or by thermal decomposition of titanium tribromide. This last reaction must be carried out either at or below 400°C, because at higher temperatures the dibromide itself disproportionates. 

The phosphides tricadrnium diphosphide [12014-28-7], Cd2P2, cadmium diphosphide [12133-44-7], CdP2, and cadmium tetraphosphide [12050-26-9], CdP, may all be prepared by indirect fusion of the elements, usually by passing phosphoms vapors, in a nitrogen or hydrogen carrier gas. 

Cadmium Bromide. The hydrated bromide is prepared by dissolution of cadmium carbonate, oxide, sulfide, or hydroxide in hydrobromic acid. The white crystalline material is cadmium bromide tetrahydrate [13464-92-1], CdBr2 4H2O, Ai/ 29s —1492.55 kJ/mol (—356.73 kcal/mol) (3)... 

Cadmium Hydroxide. Cd(OH)2 [21041-95-2] is best prepared by addition of cadmium nitrate solution to a boiling solution of sodium or potassium hydroxide. The crystals adopt the layered stmcture of Cdl2 there is contact between hydroxide ions of adjacent layers. Cd(OH)2 can be dehydrated to the oxide by gende heating to 200°C it absorbs CO2 from the air forming the basic carbonate. It is soluble ia dilute acids and solutions of ammonium ions, ferric chloride, alkah haUdes, cyanides, and thiocyanates forming complex ions. 

Cadmium Silicates. Cadmium orthosihcate [15857-59-2] Cd2SiO, (mp 1246°C d = 5.83 g/ inL) and cadmium metasihcate [13477-19-5] CdSiO, are both prepared by direct reaction of CdO and Si02 at 390°C under 30.4 MPa (300 atm) or at 900°C and atmospheric pressure ia steam. The materials are phosphors whea activated with Mn (IT) ioa and are both fluorescent and phosphorescent. 

Cadmium alkyl and aryl halides, RCdX, as weU as cadmium allyls have been prepared by Grignard reactions but, as yet, have not realized any commercially important uses despite reactivity toward a number of organic and inorganic materials. 

Cadmium acetate is a colorant for glass and textiles, a glaze for ceramics where it produces iridescent effects, a starting material for preparation of the cadmium haUdes, and is an alternative to the cyanide bath for cadmium electroplating. In 1991, cadmium acetate dihydrate sold for 59.50/kg in 2 kg lots of reagent-grade material. 

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