Organozincs cadmium halides

Transfer from Organoalumlnum Compounds. Organoaluminums are used to prepare organozinc, -cadmium and -mercury compounds e.g., trimethylaluminum reacts with Zn(OAc)2 or Znij to give MejZn. Diethylzinc can be prepared from [Et A Na (92% yield) or Et2AlCl (10%) with zinc halides. Another example is ... 

A donor such as hexamethylphosphoramide (HMPA) , dioxane or bipy , also can be added toward the end of the transmetallation to enable easier separation of the organometallic product from the metal halides present. This is particularly useful for organozinc and -cadmium preparations, because the reaction media cannot be treated with HjO to separate the metal halides, e.g., addition of HMPA to an EtjO solution containing an organocadmium product and Mg salts, MgXj, results in precipitation of MgX2 2 HMPA, thereby leaving R Cd in solution free of Mg halides, e.g. ... 

On the other hand, the consumable anode process does not allow access to less-reactive organometallic compounds such as zinc species. Indeed, the metallic ion generated by the oxidation of the anode has to be reduced at more negative potential than the halide. The use of a zinc anode indeed produces 7.n ions, which are in most cases more easily reduced than organic halides. Consequently, organozinc species can only be obtained by this method from easily reduced halides. The same remarks apply to other metals such as cadmium or copper. For example, the preparation of cadmium, zinc [5], and copper compounds [6] can be performed from CF3Br, which is easily reduced. (Scheme 15.2). 

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