Tetramethyltin

Synthesis and structure

Tetramethyltin is synthesized by reaction of the Grignard reagent methylmagnesium iodide, with SnCl₄, which is synthesized by reacting tin metal with chlorine gas.

4 CH₃MgI + SnCl₄ → (CH₃)₄Sn + 4 MgICl

In tetramethyltin, the metal surrounded by four methyl groups in a tetrahedral structure is a heavy analogue of neopentane.

Precursor to methyltin compounds

Tetramethyltin is a precursor to trimethyltin chloride (and related methyltin halides), which are precursors to other organotin compounds. These methyltin chlorides are prepared via the so-called Kocheshkov redistribution reaction. Thus, SnMe₄ and SnCl₄ are allowed to react at temperatures between 100 °C and 200 °C to give Me₃SnCl as a product:

SnCl₄ + 3 SnMe₄ → 4 Me₃SnCl

A second route to trimethyltin chloride utilizing tetramethyltin involves the reaction of mercury (II) chloride to react with SnMe₄.

4 HgCl₂ + 4 SnMe₄ → 4 Me₃SnCl + 4 MeHgCl

A variety of methyltin compounds are used as precursors for stabilizers in PVC. Di- and trimercapto tin compounds are used to inhibit the dehydrochlorination, which is the pathway for photolytic and thermal degradation of PVC.

Surface functionalization

Tetramethyltin decomposes in the gas phase at about 277 °C (550 K) Me₄Sn vapor reacts with silica to give Me₃Sn-grafted solid.

Me₄Sn + ≡SiOH → ≡SiOSnMe₃ + MeH

This reaction is also possible with other alkyl substituents. In a similar process, tetramethyltin has been used to functionalize certain zeolites at temperatures as low as -90 °C.

Applications in organic synthesis

In organic synthesis, tetramethyltin undergoes palladium-catalyzed coupling reactions with acid chlorides to give methyl ketones:

SnMe₄ + RCOCl → RCOMe + Me₃SnCl