Organotins redistribution with

Alkyltin Intermedia.tes, For the most part, organotin stabilizers are produced commercially from the respective alkyl tin chloride intermediates. There are several processes used to manufacture these intermediates. The desired ratio of monoalkyl tin trichloride to dialkyltin dichloride is generally achieved by a redistribution reaction involving a second-step reaction with stannic chloride (tin(IV) chloride). By far, the most easily synthesized alkyltin chloride intermediates are the methyltin chlorides because methyl chloride reacts directiy with tin metal in the presence of a catalyst to form dimethyl tin dichloride cleanly in high yields (21). Coaddition of stannic chloride to the reactor leads directiy to almost any desired mixture of mono- and dimethyl tin chloride intermediates ... 

Excess alkylating reagent is required if the tetraorganotin is desired as the exclusive product. In commercial practice, the stoichiometry is kept at or below 4 1, since the cmde product is usually redistributed to lower organotin chlorides in a subsequent step and an ether is used as the solvent (86). The use of diethyl ether in the Grignard reaction has been generally replaced with tetrahydrofuran. 

Organotin halides are commonly prepared by the Kocheshkov redistribution reaction, where an organic group on tin (e.g., in SnR4) exchanges (reversibly) with a halide group on tin (e.g., in SnCLt).64 Two recent examples are shown in Equations (125) and (126). The first reaction exploits the high reactivity of the Sn-Me bonds, and the second... 

Scheme 1.1.1 Synthesis of organotin(fV) compounds based on alkylation of SnCU with an organometallic reagenf and the Kocheshkov redistribution reaction...

The manufacture of OTC involves a two-step reaction. The first step can be achieved in a number of different ways and involves reaction of tin tetrachloride (SnCU) with a suitable reagent to produce various tetraalkyltin compounds (ILjSn). In the second step, It Sn reacts with SnCU in a redistribution reaction to form less alkylated organotin chlorides such as R3SnCl, R2SnCl2, or RSnCls. From these products, various other tin derivatives can be produced. A direct reaction scheme is also possible whereby the organotin halides can be synthesized by a reaction between tin metal or alloy and alkyl halides. 

---