The First X‐ray Crystal Structures of Halogenated [70]Fullerene: C₇₀Br₁₀ and C₇₀Br₁₀⋅3 Br₂

Abstract

C70Br10 ist das stabilste Produkt der Bromierung von C70, sowohl in reinem Brom als auch in o‐Dichlorbenzol. Die zehn Bromatome (orange) sind – in Übereinstimmung mit quantenchemischen Rechnungen – zu einem Ring im äquatorialen Bereich des C70‐Moleküls angeordnet (siehe Bild). Benachbarte Bromatome sind in neun Paaren in 1,4‐Position, in einem in 1,2‐Position zueinander orientiert.

Synthesis, Characterization, and Theoretical Study of Stable Isomers of C70(CF3)n (n = 2, 4, 6, 8, 10)

“…Therefore, instantaneous [14] Its addition pattern was determined by X-ray crystallography [15] and is shown in Figure 9. This high-temperature addition pattern is unprecedented for C 70 X 10 derivatives with X = H, [31] Cl, [23] Br, [32] Me, [33] Ph, [25] and tBuOO, [34] all of which were prepared at approximately 25 8C. For X = H, Cl, Br, Me, and Ph, the observed C 70 X 10 isomers all have the C sp 9 o-loop structure shown in Figure 5; for X = tBuOO, the isolated isomer has the C 2 -p 9 structure shown in Figure 5.…”

High‐Temperature Synthesis of the Surprisingly Stable C1‐C70(CF3)10 Isomer with a para7–meta–para Ribbon of Nine C6(CF3)2 Edge‐Sharing Hexagons

“…Distances and angles within the ordered CF 3 groups are normal. The estimated standard deviations (esds) for individual CÀC and CÀF distances in this structure are all 0.003 (except for the CÀF distances in the two disordered CF 3 groups), making this one of the most precisely determined C 70 -containing structures reported to date (the ranges of esds for CÀC bonds within the cage of known structures include 0.002-0.004 for two Diels-Alder monoadducts, [14] 0.004-0.006 and 0.006-0.007 for C 70 (CH 3 ) 8 [13] and C 70 F 38 , [15] respectively, and 0.02-0.03 for C 70 Br 10 , [6] C 70 (IrCl(PPh 3 ) 2 ), [16] and C 70 (Ru 3 (CO) 9 ) [17] ). In addition to further supporting [12] our earlier conclusion [18] that fullerene(CF 3 ) n compounds in general have their CF 3 groups arranged on m-and p-C 6 (CF 3 ) 2 hexagons (most of which form a continuous ribbon through edge sharing) and are not arranged on adjacent (i.e., ortho) cage C atoms as suggested by others, [19][20][21] the structure of C 1 -C 70 (CF 3 ) 10 has revealed several interesting and unanticipated aspects of C 70 X n stereochemistry.…”

“…With one exception, isolable C 70 X 10 derivatives, which include C 70 H 10 , [1] C 70 Me 10 , [2] C 70 Ph 10 , [3] C 70 Ph 9 (OH), [4] C 70 Ph 8 (OH) 2 , [4] C 70 Cl 10 , [5] and C 70 Br 10 , [6] have the "equatorial-belt" C s structure shown in Figure 1, with the ten substituents [7] positioned on a closed loop of ten edge-sharing hexagons, nine of which are para-C 6 X 2 fragments and one of which is an ortho-C 6 X 2 fragment (p 9 o(loop)). [8][9][10] The exception is the recently described compound C 70 (tBuOO) 10 , which has the C 2 structure also shown in Figure 1 with an all-para ribbon of nine edge-sharing C 6 (tBuOO) 2 hexagons (p 9 ), presumably because the tBuOO groups are too large to be on adjacent cage C atoms.…”

“…Except for X = tBu, the C s -p 9 o(loop) isomer was found to be more stable than the C 2 -p 9 isomer for these substituents (Table 1; Schlegel diagrams for the five isomers are shown in Figure 1). However, all isolable C s -p 9 o(loop)-C 70 X 10 compounds [1,[3][4][5][6] and the one isolable C 2 -p 9 -C 70 X 10 compound, C 70 (tBuOO) 10 , [11] were prepared at 25 8C and may, at least in some cases, be a kinetically stable isomer and not the isomer with the lowest DH 0 f value. On the other hand, C 1 -C 70 (CF 3 ) 10 was prepared at 470 8C, [12] a temperature that may be high enough for facile CF 3 migration to occur on the fullerene surface, a process that could conceivably result in the transformation of a less stable isomer to a more stable 10 looking down the former C 5 axis of the empty C 70 cage (50 % probability ellipsoids; only one of the two disordered CF 3 conformers is shown for each of the C73 and C74 CF 3 groups).…”

A [70]Fullerene Chloride, C70Cl16, Obtained by the Attempted Bromination of C70 in TiCl4

“…[8] The molecular structure of C 70 Cl 16 shows a remarkable combination of a chlorine belt around the equator and a skew pyramidal chlorine cap at one of the poles (Figures 1 and 2). The same belt of ten halogen atoms (Cl5-Cl9 in 1) with nine 1,4 and one 1,2 X···X contacts is also present in C 70 Cl 10 [6] and C 70 Br 10 , [9] whereas a X 10 belt without a 1,2 contact was reported recently for the C 70 (OOtBu) 10 derivative. [10] The combination of a skew pyramidal cap of six halogen atoms (Cl1-Cl4) with a cyclopentadiene fragment in the pentagon is characteristic of C 60 X 6 structures with X being Cl [1] or Br.…”