Preparation, Structural Determination, and Characterization of Electronic Properties of [5,6]‐ and [6,6]‐Carbosilylated Sc₃N@I_h‐C₈₀

Abstract

Photochemical carbosilylation of Sc N@I -C with silirane 1 afforded two corresponding [5,6]-adducts, 2 and 3, and a [6,6]-adduct, 4. The structural and electronic properties of these products were characterized by means of spectroscopic, electrochemical, and theoretical methods. The structure of 2 was disclosed by means of single-crystal X-ray crystallographic analysis. Thermal isomerization of 3 to 2 was observed, whereas that of 2 to 3 proceeded less efficiently at 100 °C. Upon heating under the same conditions, adduct 4 underwent facile decomposition to afford Sc N@I -C , or isomerized into small amounts of 2 and 3. The relative stabilities of 2, 3, and 4 were rationalized through the results of theoretical calculations. In contrast, adducts 2, 3, and 4 were stable under the photolytic conditions employed for carbosilylation. The photochemical functionalization of Sc N@I -C represents a convenient synthetic method to obtain thermally labile fullerene-based products.

Effects of Solvents on Reaction Products: Synthesis of Endohedral Metallofullerene Oxazoline and Epoxide

“…It shows a doublet at 7.76 (d, 2H) ppm and two triplets at 7.29 (t, 1H) and 7.20 (t, 2H) ppm. The UV–vis–NIR spectrum (Figure c), in which an absorption peak at 860 nm was observed, is similar to the characteristic absorptions of the reported [6,6]-closed Sc 3 N@ I h -C 80 monoadducts such as [6,6]- N -tritylpyrrolidino, [6,6]-benzyne Sc 3 N@ I h -C 80 , , and [6,6]-carbosilylated Sc 3 N@ I h -C 80 . Notably, heterocyclic adducts of EMFs are synthesized mainly via 1,3-dipolar reactions under high temperature or irradiation conditions.…”

“…The UV−vis−NIR spectrum (Figure 4c), in which an absorption peak at 860 nm was observed, is similar to the characteristic absorptions of the reported [6,6]-closed Sc 3 N@I h -C 80 monoadducts such as [6,6]-N-tritylpyrrolidino, 33 [6,6]-benzyne Sc 3 N@I h -C 80 , 34,35 and [6,6]-carbosilylated Sc 3 N@I h -C 80 . 36 Notably, heterocyclic adducts of EMFs are synthesized mainly via 1,3-dipolar reactions under high temperature or irradiation conditions. However, the heterocyclic Sc 3 N@I h -C 80 oxazoline adducts (1 and 2) were synthesized under mild conditions.…”

Photoreactions of Sc3N@C80 with Disilirane, Silirane, and Digermirane: A Photochemical Method to Separate Ih and D5h Isomers

“…As expected, 4 also worked well as a selective carbosilylating reagent for Sc3N@Ih-C80 without reaction with Sc3N@D5h-C80. Consequently, photoirradiation of a mixture of the Ih and D5h isomers and 4 in toluene for 60 h followed by HPLC separation gave pristine Sc3N@D5h-C80 and a mixture of 5a, 5b, and 6 [27], as shown in Figure 2. However, photochemical reactivity of 4 was somewhat lower than that of 1 considering the reaction time necessary to consume Sc3N@Ih-C80.…”

“…Such a separation method employing silirane 4 as an alternative derivatizing reagent was also examined based on our earlier reported result obtained from the photochemical addition of 4 to Sc3N@Ih-C80 (Scheme 2) [26,27]. In fact, it was confirmed that 4 did not undergo an addition reaction with Sc3N@D5h-C80 under the photolytic condition used for Such a separation method employing silirane 4 as an alternative derivatizing reagent was also examined based on our earlier reported result obtained from the photochemical addition of 4 to Sc 3 N@I h -C 80 (Scheme 2) [26,27]. In fact, it was confirmed that 4 did not undergo an addition reaction with Sc 3 N@D 5h -C 80 under the photolytic condition used for Sc 3 N@I h -C 80 (Figure S3).…”

“…These results led us to examine the reactivity of Sc 3 N@D 5h -C 80 for comparison with that of the corresponding I h isomer. This report describes differences in the photochemical reactivities of the I h and D 5h isomers of Sc 3 N@C 80 toward 1 as well as silirane 4 [26,27] and digermirane 7 [28,29]. Very interestingly, Sc 3 N@D 5h -C 80 was found to be photochemically inert toward 1-3, whereas Sc 3 N@I h -C 80 undergoes facile addition reactions under identical conditions.…”