Allyloxysilanes, thermolysis

It is well known that thermal decomposition of allyl-substituted silanes proceeds by retro-ene reaction with formation of transient species having a Si=C bond, such as silaben-zene, silatoluene and dimethylsilaethylene4b e. The kinetic data on the gas-phase pyrolysis of a similar allyloxysilane derivative, (l,l-dimethylallyloxy)dimethylsilane (16), and the results on thermolysis of allyloxydimethylsilane (17) in a flow system both indicate the participation of an intermediate silanone, (CH3)2Si=0 (10), as shown in Scheme 523. 

In 1989, Nefedov and coworkers have reinvestigated the thermolysis of the above-mentioned allyloxysilane derivatives 16-18 and of 2,2,6-trimethyl-2-silapyrane (21) using vacuum pyrolysis and matrix isolation techniques23. IR spectroscopic studies on the products isolated in the matrices enabled them to probe directly the intermediacy of 10 in these reactions and to discuss its thermal stability. Only in the case of allyloxydimethylsilane (17) did they find direct spectroscopic evidence for the formation of 10 by observation of its most intense band at 798 cm-1 in the matrix IR spectrum of the pyrolysis products. In all other cases silanone 10 was not detected and it was assumed that it is thermally unstable, undergoing fragmentation into SiO and CH3 radicals as shown in Schemes 7, 8 and 9 (the species actually observed in the matrix are indicated). In this paper, Nefedov and coworkers have reaffirmed the thermal and kinetic stability of dimethylsilanone 10 in the gas phase, which they had previously described19. 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

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