Crystal cadmium compounds

The colorless zinc compound, Zn(CisH6)2, which sublimes at 160° under partial decomposition, is obtained in small yield from zinc chloride and cyclopentadienyl sodium in diethyl ether however, the less stable cadmium compound decomposes, with separation of cadmium, under these conditions (55). The mercury compound, Hg(CsH5)2, is produced in 20% yield by the action of the sodium derivative on mercuric chloride in tetrahydrofuran (215). The action of cyclopentadiene on the complex K2(HgI ) in aqueous alkaline solution results in the precipitation of a mixture of CsHsHgl and Hg(CsH6)2, from which the latter compound may be obtained in good yield by extraction with a mixture of tetrahydrofuran and petroleum ether (62). It forms pale yellow crystals which begin to decompose at about 60° and which melt at 83-85°. The compound is readily soluble in most solvents it decomposes slowly even when kept in the dark at room temperature it is insoluble in water and reacts with neither water nor bases. On the other hand, decomposition occurs in dilute hydrochloric acid. It converts ferric chloride to ferrocene quantitatively, and it yields an adduct with maleic anhydride (215). 

Stabilizers are almost invariably added to PVC to improve its heat and light stability. The species found effective in stabilizing PVC are those that are able to absorb or neutralize HCl, react with free radicals, react with double bonds, or neutralize other species that might accelerate degradation. Lead compounds, such as basic lead carbonate and tribasic lead sulfate, and metal soaps of barium, cadmium, lead, zinc, and calcium are used as stabilizers. Obviously, they can react with HCl. Epoxy plasticizers aid in stabilizing the resin. Another group of stabilizers are the organotin compounds, which find application because of their resistance to sulfur and because they can yield crystal-clear compounds. 

The size of Cd nanoparticles formed at the polymerization stage increases from 6.3 nm to 300 nm as the content of the initial cadmium compound in the monomeric mixture increases from 8 to 40 wt%, respectively. Compositions formed on heating contain larger nanoparticles that have the regular hexagonal structure characteristic of Cd crystals. 

Materials like the cadmium compounds of sulfur, selenium, and tellurium, which are, respectively, yellow, red, and black, exhibit color by a mechanism we have not examined previously. Since cadmium has a d ° electronic configuration, crystal field splitting cannot be the origin of the color, but the color can be explained with recourse to a look at semiconductor properties. 

In our laboratory we have obtained a number of inclusion compounds using cadmium(II) cyanide or isopolycyanocadmate(II) as the hosts and several organic molecules as the guests. The host structures so far determined by single crystal diffraction experiments have been classified into three groups in general, 3-cristobalite-like [1], clay-like, and zeolite-like [2]. 

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