Alkali-Metal-Cadmium Compounds

T.3.2.3. Preparative Methods 7.3.2.3.2. of Alkali-Metal-Cadmium Compounds. 

The elements that form only one cation are the alkali metals (group IA), the alkaline earth metals (group IIA), zinc, cadmium, aluminum, and most often silver. The charge on the ions that these elements form in their compounds is always equal to their periodic table group number (or group number minus 10 in the newest labeling system in the periodic table). 

Cadmium sulfide also may be obtained by treatment of sodium or other alkali metal sulfide solution with that of a soluble cadmium salt. The compound also may be prepared by heating a mixture of cadmium or its oxide with sulfur at 800°C or by the reaction of H2S with cadmium vapor at 800°C. 

Rubidium metal alloys with the other alkali metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double halide salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and zinc. These complexes are generally water insoluble and not hygroscopic. The soluble rubidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide,... 

Amorphous products were obtained in the reaction between alkali metal borates and cadmium chloride, analyzed as the 2 3 7 compound (337). More recently, a patent claiming the formation of 6CdO 7B203 (3-3.8)H20 has appeared (264). 

Another example of the lack of correlation with the periodic table is provided by compounds of the alkali metals with cadmium. In the Li-Cd system there are the compounds LiCd (549 °C), LiCd3 (370 °C), and Li3Cd (272 °C). Two compounds, NaCd2 (384 °C) and Na Cdn (364 °C), occur in the Na-Cd system, and in the other three systems only one compound, KCd]3, RbCd]3, and CsCdi3, is found [2]. Compounds formed by the alkali metals are rather similar. 

The alkali metals, the alkaline earth metals, the group IIIB metals, aluminum, zinc, cadmium, and silver have ions with charges equal to their classical group numbers, but only in their compounds When the elements are uncombined, they do not form ions, and the charge on each atom is zero. 

Naming the constant type of cation involves naming the element and adding the word ion, unless a compound is being named. For example, is the potassium ion, and Ca is the calcium ion KCl is potassium chloride. The alkali metals, the alkaline earth metals, zinc, cadmium, aluminum, and silver are the most important metals that form ions of the constant type (Figure 6.2). Each of these metals forms the same ion in any of its compounds, and the charge on the ion is equal to the classical periodic group number. 

A number of stannyl-zinc and -cadmium compounds have been prepared by reaction of a tin-alkali metal compound with a zinc or cadmium halide, or a tin hydride with an alkyl-zinc or -cadmium compound. The coordination of a ligand such as a triphenyl-phosphine, TMEDA, or bipyridyl, or a solvating solvent such as DME, both enhances the nucleophilicity of the alkyl group in the alkylmetallic compounds and stabilises the stannylmetallic product. Thus triphenyltin hydride reacts with diethylzinc or diethylcad-mium in pentane or benzene with separation of metallic zinc or cadmium, but with a preformed complex, or in a coordinating solvent, the distannylmetallic compound is formed (e.g. equation 19-32). 

Compounds R3S11M, where M is an alkali metal, magnesium, zinc, or cadmium, (Sections 19.1, 19.2 and 19.7) often behave as though they are in equilibrium with RM and R2Sn , as shown in Scheme 21-2.13 14... 

Ceric fluoride, CeF4 H2O, is probably the only ceric halogen compound known in the solid form. It is a brown powder insoluble in water, prepared by adding hydrogen fluoride to ceric hydroxide. It readily forms double fluorides with the alkali metals and copper, cadmium, cobalt, nickel, and manganese. 

In conclusion, it may be stated that the succession of a-, / -and y-phases does not apply to all binary systems, for size-factor may, in some cases, determine the composition of the compounds formed. This effect is well demonstrated in the compounds CdoLi, 0d6Na and CdjjK, where the number of cadmium atoms in ihe compound increases with the size of the alkali metal atom. 

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