The Removal of Tin Residues

Trimethyltin halides are fairly soluble in water, and can often be washed out of a solution of the reaction mixture in an immiscible solvent. If the desired product is polar, it can be separated from tributyltin halides by partition between acetonitrile and hexanes, which are immiscible.52 53 

Curran has developed the chemistry of tris[2-(perfluorohexyl)ethyl]tin hydride (see Section 5.4), again with the aim of making it easy to separate the organotin byproduct.67 The polar polyethylene oxide groups of the hydrides 22-8 and 22-9 make it possible to carry out radical reactions in aqueous solution.68-69 

An alternative solution is to use organotin reagents supported on an insoluble, but porous, polymer at the end of the reaction, the polymer can be filtered off, and the catalyst can be regenerated.72 Most of the work in this field has involved polymer-bound tin hydrides (for hydrogenolysis of halides, thiocarbonyl compounds, or hydrostannation of ketones),73-76 but also tin chlorides (for use as Lewis acids),77 allylstannanes (for allyla- 

The organotin group is usually attached to the polymer (usually polystyrene) by using conventional organotin methodology, for example 82 

In a rather different approach, the oligomeric stannanes 22-10 and 22-11 have been prepared by treating the living polyethylene or polystyrene anions with the appropriate tin halide. These stannanes are soluble in boiling toluene, where they can be used for reducing alkyl or aryl halides, but on cooling the organotin compounds separate and can 

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