Photochemical addition disilane

Further investigations on the photochemical bissilylation of C6o with disilanes [275c] indicate that 3C o and Qo do not play an important role in these reactions due to the fact that no absorption band for the C6o radical anion is observed in the course of the reaction and the decay of 3C 6o is not accelerated by addition of the disilanes. Another hint for the involvement of the phenylsilyl radical is that no product is formed upon irradiation at >300 nm where the cleavage of the disilane does not take place. The radical reaction pathway is further confirmed by a lower yield obtained by addition of radical scavengers. 

Ando demonstrated that the photolysis of partially tert -butyl-substituted disilanes 45 in the presence of Cgo results in the formation of 1,16-adducts 46 in 54-62% yield (Scheme 8)37,38. Interestingly, unusual adducts similar to 49 were obtained as by-products with disilanes having trimethylsilyl substituents (Scheme 9). The authors explain these observations by a mechanism involving the intermediacy of silyl radicals which are generated photochemically by Si—Si bond homolysis. Initial free-radical addition of silyl... 

The photochemically induced addition of bulky disilanes to C6o has already been discussed in Section IV.A.l.h, as it affords the unusual inherently chiral 1,16-addition pattern (( )-72, Figure 1.20). In this reaction some phenyl-substituted disilanes give rearranged adducts of the type ( )-73 (Figure 1.20).197,404 Further [60]fullerene derivatives with stereogenic centers in the addends were obtained in photoinduced addition-rearrangement reactions with 3,4-bis(alkylidene)-l,2-disilacyclobutanes 405 and with octaaryl-substi-tuted cyclotetrasilanes and -germanes406... 

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