Cadmium alkyl

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. 

Organometallics, such as dialkyl zinc or cadmium-alkyl or aryl lithium Alkali acetylides Diels-Alder Arndt-Eistert... 

In contrast to the chemistry of the zinc complexes [TpRR]ZnR, the cadmium alkyl derivatives have not been used to prepare an extensive series of half-sandwich [TpRR]CdX complexes. However, several [Tp JCdX complexes supported by sterically demanding tris(pyrazolyl)hydroborato ligands, e.g., [TpBut]CdCl (98), [TpBut]CdI (91), [Tp lCdl (91), and [TpBut,Me]Cd(Tj2-02N0) (91), have been synthesized by metathesis between CdX2 and either K[TpRR ] or Tl[TpRR ] [Eq. (15)]. 

Metal alkyls can be prepared in a simple manner from the main group halides (X = Cl, Br, I) and the appropriate alkyl Grignard reagent (RMgl) or the alkyllithium salt (RLi), as shown for the cadmium alkyls (Equation (2)).13 The elimination of impurities from the precursor source is of great importance, as any remaining impurities are invariably carried over into the growing semiconductor layers. Incorporation of impurities, even at levels as low as 1015 free carriers per cubic centimeter (one part in ca. 107), can drastically affect the electronic properties of the... 

The reaction of dabco (l,4-diazobicyclo[2.2.2]octane) with Me2Cd yields a 1 1 adduct 197, which adopts a linear polymeric structure (Figure 34).255 The cadmium atom is coordinated by two dabco units and two methyl carbon atoms giving rise to a distorted tetrahedral environment. Finally, the organocadmium adduct 198 (Figure 35) has been isolated from the reaction of Me2Cd with Cd[(SeP-/-Pr2)2N]2.256 The solid-state structure consists of dimeric units where each methylcadmium unit is coordinated to three selenium atoms. The geometry about the cadmium center is tetrahedral with a Cd-C distance of 2.16 A, which is comparable to that observed in other cadmium alkyl complexes. 

The basic assumption is made in these calculations that the benzyl or phenyl radicals formed are removed in the hot zone only by recombination with methyl radicals. When dimethyl zinc is used, the apparent energy of activation for reaction (11) is negative indicating a loss of phenyl radicals in the hot zone by an additional process. The only species present which is absent when the mercury and cadmium alkyls are used is ZnCH3. The additional process by which phenyl radicals are lost is therefore probably... 

Zinc and cadmium alkyls have not been successful as stereospecific catalysts in the absence of co-catalysts, presumably because they do not complex strongly enough with the monomer and the metal-carbon bonds are too covalent. Cadmium alkyls were first reported by Furukawa and coworkers (260) to induce vinyl polymerization, but it was shown later (267, 262) that oxygen was a co-catalyst and the reactions were free radical in nature. Similar free radical results were obtained with zinc alkyls (261—263) and vinyl monomers. However, with more basic and more easily polarized monomers, such as olefin oxides and aldehydes, the zinc catalysts operate by a coordinated anionic mechanism (250). 

A Variety of ketones may be made using cadmium alkyls (50-70%). In the preparation of alkyl aryl ketones, reaction of the aliphatic rather than the aromatic anhydride is preferred. Keto acids result when phthalic anhydride or dimethylsuccinic anhydride (60-70%) is used. 

Addition of cadmium alkyls to acyl chlorides yields the corresponding ketones. The method has been reviewed, and the experimental condi-... 

The following cadmium alkyls may be prepared in a similar manner, the yields being shown in each case —... 

Cadmium alkyl, 28, 75, 79 Cadmium chloride, 28, 75 Calcium carbonate, 22, 54 Calcium chloride, 23, 103 M-Caproic acid, 21, 13 CAPROIC ACID, a-CYANO, ETHYL ESTER, 26, 31... 

Cadmium alkyls, obtainable from Grignard reagents and cadmium chloride,329 also lead to ketones when treated with acid chlorides ... 

Linear organomercurials provide a convenient basis for the investigation of the effect of susbstitution in the organic moiety on the metal chemical shift. Increase in the shielding of 150 ppm are observed for each substitution of Me for a H in Hg-CH3 derivatives, while smaller decreases in shielding ( 30 ppm) occur on substitution of )S-Hs. Cadmium alkyls show a similar behavior, but for silyl mercury compormds, replacements at both a and position results in deshielding. 

Thus it seems that > D2 in zinc and cadmium alkyls, although less strongly so than in mercury alkyls, and that inequalities also apply to the D values in BiMc3, SbMe3, and Me2SnCl2. Price and Trotman-Dickenson 133) have tentatively deduced that Z>3 < 19.2 kcal/mole in Me3Bi in this event, the thermochemistry requires Dj = 44, D2 39, < 19, i.e.,... 

Metallorganic chemical vapor deposition (MOCVD) is now widely used in the preparation of III-V and II-VI devices. In addition to the hydride gases used as source materials in other CVD systems (e g., arsine and phosphine), less toxic liquid alternatives (e.g., tertiary butyl arsine and tertiary butyl phosphine) are also used in MOCVD systems along with other toxics such as cadmium alkyls and mercuiy.[42][43]... 

Cadmium alkyls are useful reagents in organic chemistry for the conversion of acyl halides to ketones. They are prepared in situ by the direct addition of anhydrous CdCl2 to an ether solution of the Grignard reagent. 

Table 2 summarises results for species of reasonably certain composition in solution. Cadmium salts of alkyldithiophosphates or dialkyl dithiocarbamates are not included as they are rapidly exchanging even at 250 This is likely to be true of the complexes with xanthate and S2CC(CN) -, although the latter gives rise to a very deshielded " Cd environment, 813 ppm in DMSO solution. " A detailed listing of results for cadmium alkyls is given in Ref 1. 

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