Silanimines complexes

Berry describes a variety of reactions of the silanimine complex 788 to give 818-821348-350. The phosphine ligand is quite labile and can be replaced by CO yielding the carbonyl complex 818 (equation 282). 

While r 2-coordination of silanimines has been realized in species such as Cp2Zr(r 2-SiMe2=Nt-Bu)(PMe3) [13], no -(silanimine) transition metal complexes are known so far [14 - 16]. Access to these Si=N systems is opened up by treatment of 19b,c with Me3P=CH2 at low temperature leading to elimination of hydrogen chloride and formation of the fert-butyl and mesityl-N-derivative 23a,b. These species are stable only for a short period in solution (two hours in toluene at -30°C), but can be... 

In a number of ways the reactions of stable silylenes resemble those of phosphines, R3P, to which they are isolobal analogs. Examples are provided by the reactions of 59 with covalent azides. Phosphines are known to react with azides to give phosphineimines, Ph3P=NR. In similar fashion, 59 reacted with triphenylmethyl azide in THF to give the silanimine 72 as its THF complex (equation 109)148. This reaction provides a new method for synthesizing compounds containing Si=N double bonds, which have previously been made by salt elimination reactions375. 

Reactions of 59 with less hindered azides can be more complex. With trimethylsilyl azide, the isolated product was the azidosilane 73. The formation of 73 can be rationalized, however, as proceeding through the initial formation of a silanimine, followed by addition of MesSi—N3 across the Si=N double bond, as shown in equation 110. When 59 was treated with 1-adamantyl azide, the product was the silatetrazoline 74. Once again this product may have resulted from initial formation of a silanimine, followed in this case by 2 + 3 cycloaddition of the azide to the Si=N double bond (equation 111)98 148. 

The pyrolysis of [dimethoxy(methyl)silyl]bis(trimethylsilyl)amine350 yields products which can be ascribed to an initial formation of N-(trimethylsilyl)-methoxy(methyl)silanimine (equation 165). The isolated dimers may be formed by the imine dimerization or possibly by an attack of the silanimine on the precursor instead. Additional evidence for the presence of some of the intermediates postulated to account for the results was obtained by a study of the copyrolysis of [dimethoxy-(methyl)silyl]bis(trimethylsilyl)amine and hexamethylcyclotrisiloxane, which yielded a fairly complex mixture of products351. The formation of product 88 most likely proceeds through the unsaturated eight-membered ring silanimine 89 and not by way of meth-ylsilanitrile, although the latter possibility was also considered by the authors (equation 166). 

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