Organylhalostannanes. The C—Sn Bond Cleavage

Among the first organotin compounds of special importance are the organylhalostannanes R4 SnX . We would like to review here their development and approach to their synthesis in the absence of metallic tin, other metals or organometallic compounds, which have not been considered in the previous sections. Their properties will be considered as well. 

In 1871, Ladenburg606 was the first to study the reaction of SnCl4 with a nonsymmetric tetraorganylstannane. As a result Et2SnCl2 and EtPhSnCl2 were obtained from Et3SnPh. 

In 1936 Kocheshkov, Nesmeyanov and Puzyreva820 found that HgCl2 cleaved the Sn—Sn bond in both RjSnSnRj and (R2Sn) with the formation of R3S11CI and R2SnCl2, respectively. 

In the first half of the 20th century it was shown that the C—Sn bond in organotin compounds, especially in tetraorganylstannanes, was easily cleaved by both heterolytic and homolytic mechanisms. This fact makes the C—Sn bond quite different (regarding its thermal and chemical stability) from the C—Si and C—Ge bonds and brought it close to the C—Pb bond. In 1945, Waring and Horton835 studied the kinetics of the thermal decomposition of tetramethylstannane at 440-493 °C, or at 185 °C at a low pressure 

In 1958, Prince and Trotman-Dickenson837 studied the thermal decomposition of Me2SnCl2 at 555-688 °C in the presence of toluene as the radical carrier. The process proceeded homolytically according to equation 9. 

Sixty publications in the period before 1960, reporting the use of the cleavage of R4Sn for organylbromo- and organyliodonstannane syntheses by halogens (mainly bromine and iodine), were reviewed . 

For the first time tetraiodostannane was used in the reaction with tetraalkylstannanes by Pope and Peachey in 1903. They demonstrated that heating Me4Sn with Snl4 at 100°C led to MesSnl and MeSnD. Pii4Sn did not react with SnD even at 240°C. 

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