The cadmium dialkyls (dimethyl, diethyl, dipropyl, dibutyl, etc.) are procurable in good yields from anhydrous cadmium bro mide and the appropriate magnesium alkyl bromide. Cadmium dimethyl, Cd(CH3)2 is a colourless liquid boiling at io5° C (E. Krause, 1917). Mercury possesses a remarkable capacity for combination with the carbon of hydrocarbon groups and of or ganic radicals in general. Sodium amalgam acts directly on ethyl iodide and bromobenzene, giving respectively mercury diethyl, (b.p. 159° C), and mercury diphenyl, Hg(C6115)2 (m.p. 12o° C). With certain reactive substances such as aro matic bases or phenols, mercury derivatives are obtained merely by boiling with mercuric acetate; aniline yields o- arid p-amino phenylmercuriacetates, whereas m-toluidine takes up two and even three mercuriacetate residues. Phenol gives rise to o- and p-hydroxyphenylmercuriacetates and hydroxypheny1-2 :4-dimercu riacetate. In addition to the foregoing processes, organo-mercury compounds are conveniently prepared through the agency of Grignard reagents. Mercury dimethyl, a colourless liquid boiling at 89-92° C, is obtained from magnesium methyl iodide and mercuric chloride, and the homologous mercury dialkyls are pre pared similarly.
Organic derivatives of indium and thallium are obtainable through the Grignard reagents. Thallic bromide, but not thallous bromide, yields both dialkyl and diaryl compounds. 'Malik di methyl bromide, forms silvery-white leaflets (R. J.
Meyer and A. Bertheim, 1904), whereas thallic diphenyl bromide, is obtained in colourless transparent microscopic needles (D. Goddard and A. E. Goddard, 1922).
ethyl is drained from the by-product, sodium chloride, and dis tilled in steam. It is thus obtained as a colourless liquid, stable in air and boiling at 200° C. For use as an antidetonant, lead tetraethyl (54.5%) is mixed with ethylene dibromide (36.4%) and Halowax oil (9.o%) containing a distinctive red aniline dye, and this "ethyl fluid" has a specific gravity of 1.79/20° C.
Lead tetramethyl, obtainable by similar processes to its tetra ethyl homologue, is a colourless liquid boiling at Io° C. These two lead tetralkyls and their homologues are obtainable through the appropriate Grignard reagents but this reaction goes smoothly only in the case of lead tetra methyl, for with the homologous alkyl compounds unsaturated lead trialkyls, are formed as by-products. The four alkyl groups attached to lead can be removed in stages by the action of halogens, and different alkyls can then be substituted for the halogen atom. In this way many mixed lead tetralkyls have been prepared (G. Griittner and E. Krause, 1917). When prepared from magnesium phenyl bromide, lead tetraphenyl, Pb(C6H5)4, is accompanied by lead triphenyl, Pb(C6H5)3, and lead tri-p-tolyl, and lead tri-p-xylyl, have also been de scribed (Krause and M. Schmitz, 1919).
Griittner and Krause have prepared a cyclic lead compound, diethylcycloplumbipentane, from diethyl lead dichloride and the dimagnesium compound of :5–dibromopentane. Stannous chloride and magnesium ethyl bromide give tin diethyl, as an oxidisable oil insoluble in water (P. Pfeiffer, 1911), whereas tin diphenyl, Sn(C6H5)2, a bright yellow powder melting at 13o° C to a dark red liquid, is obtained from stannous chloride and magnesium phenyl bro mide. When excess of Grignard reagent is used, this diary] compound loses half its tin and passes into hexaphenyldistan nane, 3Sn(C8H5)2=Sn+ obtained in col ourless plates melting at 237° C (E. Krause and R. Becker, 192o). Tin tetramethyl, Sn(CH3)4, and tin tetraethyl, boil ing at 78° C and '75° C respectively, are prepared in good yields from stannic chloride and the appropriate Grignard reagents; in the latter case triethylstannic chloride, is obtained as a-by-product.
Magnesium benzyl chloride and stannic chloride give tribenzyl stannic chloride, (m.p. C) and tin tetra benzyl (tetrabenzylstannane), (colourless needles, m.p. 42-43° C). The former compound when acted on by iodine furnishes dibenzylstannic chloride in colourless crystals melting at 163-4° C (Smith and Kipping, 1912).