Silicon-nitrogen bond cleavage

Activation Energy for Silicon-Nitrogen Bond Cleavage (eq. [103])... 

Cleavage reactions of the silicon- nitrogen bond of silylamines by TeF6 affords aminotellurium(VI) fluorides (73, 74, 76) as in Eq. (13), where n = 1, 2 ... 

Alkyl and Aryl Derivatives.—The cleavage of silicon-nitrogen bonds in A-silylphosphazenes by reactions with phosphorus and silicon halides has been studied in some detail. For example, with phosphorus trichloride a novel tri(phosphazenyl)phosphine is obtained ... 

The formation of Si-N-B bond linkages has mostly been accomplished one of following methods so-called cleavage reactions, in which a silicon-nitrogen bond is cleaved by a covalent halide leading to the formation of some halosilane as a side product and dehydrohalogenation, in which the elements of a hydrogen halide are eliminated [17]. 

Such reactions are known to occur at about 2S0°C for monoaminosilanes reacted with a second type of amine [IS]. Amines incorporated in a polysilazane network require higher temperatures for the transamination because of steric hindrance and the necessity to cleave-rebuild simultaneously two Si-N bonds. Transition metal catalysts can reduce the temperature requirements. In early studies [16] of the transition metal-catalyzed polymmzation of silazanes, we observed the catalytic cleavage of Si-N bonds at temperatures below 1S0°C and the ability to metathesize silicon nitrogen bonds. The transamination reactivity occurs at temperatures below that of the carbonization and carbidization of the organic groups. 

Finally, silicon-nitrogen bonds are also labile in the presence of electrophiles, and this concept has been used by Komatsu in development of a silylimine linker (Table 1.16, Entries 12-14). Multifunctional cleavage was achieved with a range of electrophiles. For example, treatment with TFA left a hydrogen residual at the point of attachment (Table 1.16, Entry 12), while benzoyl (Table 1.16, Entry 13) and allyl (Table 1.16, Entry 14) groups were introduced by cleavage with benzoyl chloride and allyl iodide, respectively. 

When a thin liquid film with a thickness of approximately 2 pm prepared by spin coating of a 15% benzene solution of polymer 1 was irradiated with a 500-W Xe-Hg lamp for 300 s in air, a transparent solid film was obtained. The UV spectrum of this solid film shows that an absorption at 235 nm due to phenyldisilanyl units vanishes after UV-irradiation (Figure 1). This clearly indicates that photolytic cleavage of silicon-silicon bonds leading to the cross-linking occurred. Similar photolysis of the thin liquid films under a nitrogen atmosphere again afforded transparent solid films whose UV spectra show no absorption at 235 nm due to phenyldisilanyl units. 

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