Verfahren zur Herstellung von Dialkylzinndihalogeniden

Di- and tri-alkyl tin halides are prepared by reacting alkyl halides with tin at e.g. 130-170 DEG C. in the presence of metal halides and organic Lewis bases. The latter include alcohols, polyalkylene glycols, mercaptans, esters, organic phosphites, ketones, ethers, nitriles and thioethers. Preferably, compounds having two Lewis base groups, separated by two or three carbon atoms, i.e. chelating agents, are used, e.g. acetonyl acetone. The most preferred compounds have two such groups of different power, e.g. b -acetyl diethyl ether, b -ethoxy propionitrile, b -ethoxyethyl acetate and b -ethoxyethanol. Preferably at least sufficient compound is used to co-ordinate completely with the metal of the catalyst. Halides of metals of Groups 1, 2 and 3 of the Periodic Table are the preferred catalysts. These may be added as such or formed in situ by reaction between the alkyl halide and the appropriate metal, metal salt or alkoxide. When the Lewis base compound is a phosphite, e.g. tri-phenyl phosphite, sufficient tin halide is formed from the tin and alkyl halide in the reaction mixture to obviate the addition of further metal halide. The preferred alkyl halide is the alkyl bromide containing 2.5 to 5% alkyl iodide. When dialkyl tin halides are the desired product, it is desirable to carry out the reaction under anhydrous condition on an inert atmosphere. The alkyl tin halides may be hydrolysed to the corresponding oxides or hydroxides.