Organo-Metallic Compounds

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.

Third Series.

Aluminium trialkyls and triaryls have been re corded, and the production of these substances is facilitated by the use of Grignard reagents. Magnesium ethyl bromide and an hydrous aluminium chloride interact in dry ether to produce aluminium triethyl etherate, as a colour less mobile liquid boiling at 112° C/16 mm. It fumes in air, takes fire spontaneously and is decomposed explosively by cold water, (E. Krause and B. Wendt, 1923). Aluminium diethyl iodide (b.p. 118-12o° C/4 mm.) and aluminium ethyl diiodide (m.p. C; b.p. 158-16o° C/4 mm.) were obtained by V. Grignard and R. L. Jenkins (1925) from the liquid product of the interaction of aluminium and ethyl iodide.

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).

Fourth Series.

Organic derivatives are known of silicon (q.v.), germanium (q.v.), tin and lead. The commercially im portant lead tetraethyl, known under various names, as tetraethyl lead, lead ethide, etc. was formerly obtained by the interaction of Frankland's reagent, zinc diethyl, and lead chloride. It is now manufactured in the U.S.A. by the action of gaseous ethyl chlo ride under pressure on a powdered alloy of lead and sodium con tained in an autoclave with heat control. The liquid lead tetra

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).