Methyl group exchange

Wells and coworkers53 have prepared a series of deuterated tetramethyltin compounds, which they used to study the long-range deuterium isotope effects on the proton chemical shifts of tetramethyltin. The various deuterated tetramethyltin compounds, with one to four trideuteromethyl groups on the tin atom, were prepared by a series of methyl group exchanges beginning with tri-trideuteromethyltin chloride and undeuterated tetramethyltin (Scheme 12). 

Finally, hydride for methyl group exchange may have been involved (2/6) in a reaction with/ran.s-[PtIH(PMe3)2] [Eq. (67)]. The hydridogold(I) species, if that was indeed the product obtained, underwent further reaction to yield a probable gold cluster compound. 

It has also been found that 7Li and the methyl group exchange between methyllithium and the complexes at comparable rates. While a distinction between the two above mechanisms cannot be made directly, Seitz and Brown indicate that the second mechanism is the predominant path for exchange. The data for these systems are collected in Table II. 

It is of interest to examine the reason for the absence of polymerization in the isobutylene-Al2Me6-n-pentane system. According to our NMR results, methyl group exchange is decidedly faster in the presence of isobutylene than in pure cyclopentane, and consequently if the isobutylene monomer itself is able to interact with Al2Me6, by analogy with... 

It was also reported that using methyJJithium instead of the methyl Grignard could give some racemization of methyl p-tolyl sulfoxide as a result of methyl group exchange via a methylene sulfine intermediate. ... 

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