Cadmium derivatives

Metal selenolates of the type M(SeAr)2 (M = Zn, Cd, Hg) are usually insoluble, polymeric compounds. Intramolecular Se N coordination has been employed to stabilize monomeric mercury selenolates, e.g., 15.27, but this approach was not successful for the zinc and cadmium derivatives. ... 

Docosanedioic acid has been prepared by Wolff-Kishner reduction of 6,17-diketodocosanedioic acid, formed by reaction of the half-ester acid chloride of adipic acid with the a,co-cadmium derivative of decane (%26 overall yield).3 Reduction of Wolff-Kishner method, followed by simultaneous reduction and desulfurization with Raney nickel of the 2,5-bis(co-carboxyoctyl)thiophene pro-... 

The coordination modes of the nitrate ligand in the complexes [TpBut]M(N03) (M = Cu, Ni, Co, Zn) are summarized in Fig. 46. (171, 184). Evidently, the coordination mode varies from unidentate for Zn to symmetric bidentate for Ni and Cu, with the cobalt derivative exhibiting an anisobidentate coordination mode. Moreover, the related cadmium derivative [TpBut,Me]Cd(N03) also exhibits bidentate coordination of the nitrate ligand, with Cd-0 bond lengths of2.272(6) A and 2.295(7) A (91). Such symmetric bidentate coordination contrasts with the significantly different Zn-0 interactions [1.978(3) A and 2.581(3) A] in unidentate [TpBut]Zn(N03). The coordination modes for a variety of [TpRR ]M(N03) complexes are summarized in Table VIII. 

Complexation and determination of formation constants has been studied with the tetramethyl-cyclam (l,4,8,ll-tetramethyl-l,4,8,ll-tetraazacyclotetradecane) ligand.686 A series of zinc N4 donor macrocyclic complexes with different ring sizes were synthesized and characterized for comparison with cadmium derivatives.687... 

Aromatic electrophilic substitution has also been used in the synthesis of arylcadmium species. In a recent example, aniline was shown to undergo electrophilic metallation upon treatment with Cd(OCOCF3)2, yielding the /wra-substituted cadmium derivative 183 (Equation (61)).246... 

The metathesis reaction of fluorinated alkyl iodides with reagents such as CdMe2 is a well-established procedure for the synthesis of fluoroalkyl cadmium derivatives. A recent application of this method has allowed for the synthesis of compound 186, as shown in Scheme 22.248 This reaction is accompanied by formation of 187, which results from the insertion of the difluorocarbene in the methyl-cadmium bond. Presumably, the difluorocarbene is generated by a radicalar process involving HCF2I and CdMe2. 

It should be noted that the use of certain inorganic pigments, especially those derived from cadmium derivatives and lead chromates, pose considerable toxicological risks and their use is now subject to legislation in most countries. 

The metatheis of acetates with the alkali alkoxides (method 5) can be used for the preparation of the methoxides and ethoxides of all three elements and is the only reaction leading to Hg(OR)2 [1623]. The trans-esterification of Zn(OMe)2 (method 6), according to [1121], can be carried out only in the presence of LiOR (forming soluble bimetallic complexes). The direct electrochemical synthesis on the anodic oxidation of metals in alcohols has been described for Zn(OEt)2 and a series of cadmium derivatives (Cd(OR)2 — obtained in the presence of such donor ligands as Dipy, Phen, and Dmso [98]) (method 2). 

Of the bis(trifluoromethyl)cadmium derivatives obtained to date, the glyme adduct, (CF3)2Cd glyme, is the best compromise between chemical reactivity and thermal stability this compound appears to be almost a classic example of a lightly stabilized species, one which is stabilized enough to be isolatable but which is still quite reactive (107). That this material is a much more effective reagent than, for example, (CF3)2Cd 2 pyridine, can be most easily seen from the results of the reactions of these compounds with a second class of substrates, the halides of germanium and tin. Within 15 min at ambient temperature... 

The above stereospecific tiirane polymerisations have generally been run in heterogeneous systems. Such conditions essentially make it impossible to determine the detailed structure of active species involved in these polymerisations. Thus, enantiosymmetric and enantioasymmetric polymerisations of propylene sulphide have also been studied in a homogeneous phase by using chiral cadmium thiolates of cysteine esters and chiral cadmium carboxylates of cysteine and methionine [157,160-164]. The most studied is living polymerisation using the cadmium derivative of the isopropyl ester of (.S)-cysteine [160] ... 

DiaUcyl- and diarylcadmium derivatives are colorless compounds that are either liquids or low-melting solids. The compounds are noticeably more stable to air than the corresponding zinc derivatives. For example, whereas Me2Zn is pyrophoric, Me2Cd only fumes in air. However, although the cadmium derivatives are more air stable, they are substantially... 

Dangerous levels of human exposure from diet have occurred, most notably in Fuchu, in northern Japan where rice was eaten that was contaminated with cadmium derived from an old zinc mine and present in soil and water. Low calcium intake and vitamin D deficiency may also have been factors. The victims suffered from brittle bones, and it became known as itai-itai disease from the Japanese for ouch-ouch (see box). The village of Shipham in Somerset was, similarly, found to have very high levels of cadmium in the soil, which also derived from an old zinc mine. 

While the zinc and mercury derivatives are stable in benzene-dj solution for at least 3 days, the cadmium derivative is much less stable. The Si NMR shifts for these compounds move to lower field on descending the... 

This procedure consists of refluxing an acetone solution of the /3-keto imine with a freshly prepared metal hydroxide. The product precipitates from solution upon cooling or is obtained by dilution of the acetone solution with water. The method has been used to prepare the copper(II), nickel(II), and cobalt(II) derivatives of a variety of /3-keto imines, - but attempts to prepare zinc and cadmium derivatives were not successful. The advantages of this procedure have been described previously. On occasion, the chelate compound may precipitate during the reaction... 

The procedure described failed completely when a secondary bromide, 2-bromopentane, was used however, when the cadmium derivative was prepared at —5° to —7° and allowed to react in ether at this temperature with /3-carbomethox ropionyl chloride, methyl 4-keto-5-methyloctanoate was obtained in a yield of 19.3%, b.p. 130.5-130.7721 mm. 

Methyl 4-keto-7-methyloctanoate has been prepared only by the procedure given, which is based on the method of Cason and Prout. The use of cadmium derivatives for the preparation of simple ketones was introduced by Gilman and Nelson. ... 

Furthermore, structural features (Table V) of Cd9(OC2H4OMe)18-(HOC2H4OMe)2 (Fig. 55) reveal it to be related to that of the calcium analogue (Fig. 54). although a lower coordination number is observed for cadmium(II), which is smaller than calcium(II). The molecular structure of the cadmium derivative consists of a centrosymmetric nearly planar arrangement of nine cadmium atoms with the overall structural formula being [Cd9(/i3,... 

The reaction of the cadmium derivative of diethyl 1-bromo-1,1-difluoromethylphosphonate with aryl iodides proceeds smoothly in DMF at room temperature in the presence of CuCl to give diethyl oc,oc-difluorobenzylphosphonates in excellent yields (70-88%, Scheme 3.72). A variety of functional groups, such as nitro, ether, ester, halide, azo, urethane, as well as free carboxylic acid are tolerated by the read ion. " ... 

Metal-Nucleoside, -Nucleotide, and-Nucleic Acid Interactions.—The crystal structure of a cadmium derivative of cytidine 5 -monophosphate [Cd(5 -CMP)(H20)]H20 has been reported, in which cadmium is bonded to the N(3) position oh the base, to a phosphate oxygen from each of three other 5 -CMP groups and to a water molecule. In the crystal of bis-(8-azahypoxanthinato)tetra-aquocadmium(ii), the metal is six co-ordinate, two purines being co-ordinated to cadmium through N(7). ... 

A wide range of acetals may be prepared by allowing dialkyl-cadmium derivatives to react with the intermediate 1,2-acetoxonium ion.56 The bulky, dialkylcadmium presumably approaches from the least-hindered side (exo), leading to the formation of only one isomer. 

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