Controlled two-step nucleophilic hydroalkylations, hydroarformed. In all cases the addition takes place at a double bond ylations as well as hydrostannylations of fullerene-60 (1) and separating two six-membered rings of the fullerene core. In fullerene-70 (2) lead to defined organodihydrofullerenes this way a variety of organodihydrofullerenes also carrying CWHR and C,,HR. NMR investigations show that only one functional groups have been synthesized. isomer of each organodihydrofullerene with C, symmetry isThe spherical all-carbon Ih molecule fullerene-60 (C,) consists of 12 isolated pentagons and 20 hexagons. Structural data"] and calculations [*] demonstrate that the bonds between two hexagons (6 -6 bonds) exhibit double-bond character. The bonds between the pentagons and hexagons (5 -6 bonds) with single-bond character are significantly longer, also showing a much lower electron density. Therefore, fullerene-60 can be considered a sphere built up of fused [Slradialene and cyclohexatriene units. This structural argument is supported by its chemical reactivity. One-step additions to c60, namely the addition of osmium tetroxide ['], transition-metal complexes[41 or 1,3-dipolesr5I, exclusively take place at the 6-6 bonds. The other important chemical property of Cs0 (1) is its high electrophilicityt6I and affinity towards radicals[71. Due to the polyfunctionality (thirty 6 -6 bonds), an uncontrolled reaction leads to a huge number of different addition products which are impossible to isolate. Only few examples for the preparation of isomerically pure single compounds are k n~w n [ ' -~, * -~'~ . R ecentlyP1, we have shown that it is possible to control even two-step nucleophilic additions to a 6 -6 bond and to isolate the isomerically pure organodihydrofullerenes 1-tert-butyl-and l-ethyl-l,9-dihydrofullerene-60"*l (5b and 5c). Thereby 1 was titrated with tert-butyllithium or ethylmagnesium bromide and subsequently protonated under HPLC control. This method opens up the access to a variety of functionalized organodihydrofullerenes which for example can serve as precursors for further reactions. Independently, 5b was In this paper we show that the titration method ['] can generally be used for the hydroalkylation and hydroarylation of fullerene-60. Also the addition of radicals can be controlled quantitatively by HPLC. In this way we prepared a variety of isomerically pure 1,9-adducts of 1 and determined their spectroscopic properties. For the first time we performed the additions of nucleophiles to fullerene-70 (2) by using our titration method and showed that also in this case single regioisomers with C, symmetry are formed. Results and Discussion Synthesis of Organodihydrofullerenes 5 -8Cs0 (1) and C70 (2) were treated with various nucleophiles in benzene because besides carbon disulfide mainly aromatic solvents guarantee a sufficient solubility. The nucleophile addition, carried out stepwise, leads to a dark brown precipitate of the fullerides 3, 4 and C70R-, which upon rapid stirring is suspended homogeneou...

For the structural variation of fullerenes three strategies can in principle be considered: 1) the synthesis of exohedral adducts, 2) the formation of heterofullerenes in which one or several C atoms of the fullerene core are replaced by, for example, N or B atoms, and 3) the generation of endohedral complexes. Whereas both exohedral and endohedral derivatives can be synthesized and isolaled by ;I variety of methods.['] it has not been possible s o far to produce macroscopic amounts of heterofullerenes.r'l Even the mass spectrometric detection of heterofullerenes was accomplished only for boron fullerenes C,,_,,B,+ (n = 1 -6), which were gcnerated in situ by laser vaporization of boron/ graphite composite rods.131 We now report for the first time on the formation of the nitrogen heterofullerenes C,,N+ and C,,N+, which are isoelectronic with C,, and C,,. These ions are formed by fragmentation (FAB-MS) of regioselectively synthesized iminofullerene derivatives. The specific arrangement of the nitrogen addends tacilitates the removal of a carbon atom from the fullerene core and the incorporation of a nitrogen atom.Bisarafullci.oid 3[4' served as a precursor for compounds leading to C,,,N'. and we synthesized for the first time the bisadducts 2. which directly fragment to form this heterofullerene ion (Scheme 1. Table 1). The C;-symmetric compounds 2, which are / R N la,b I 2a,b II Schemc I . a R = ('OOEt. b: R = COOrBu. Reaction conditions: a) N , R , 1chloronaphth;iI~ii~. 60 C: b) toluene, reflux.

No abstract

Amino acid and amido derivatives of Ce0 were synthesized by direct additions of the corresponding diazoamides to the fullerene core.

The electrochemical properties of four singly bridged (1-4) and one doubly bridged ( 5) N-substituted imino[60]fullerenes have been investigated with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The substituents on the imino nitrogen are methoxycarbonylmethyl (1, 2, 5), 4-(pentafluorophenoxycarbonyl)phenyl (3), and 4-(succinimidoxycarbonyl)phenyl (4). [6,6]-Bridged structures (2) with closed and [5,6]-bridged structures (1, 3, 5) with open transannular bonds were compared for the first time. Whereas C 60 and 1-4 exhibit four successive, reversible reduction peaks in terms of an EEEE mechanism, a chemical reaction followed the cathodic reduction of 5 to 5 Ϫ . This effect is particularly clear in the DPV, where all subsequent reduction peaks were doubled. This can be explained by an ECEEE mechanism, in which 5 after the first E reduction undergoes a chemical transformation into one or two new species, which are further reduced in EEE processes. In the anodic oxidation of 1-5 a two-electron transfer was confirmed. In sharp contrast to all other fullerene derivatives, a quasireversible oxidation of 4 could be observed. To our knowledge, this is the first report of a quasireversible electrochemical oxidation for C 60 mono adducts. The reduction potentials exhibit good linear relationships with the calculated LUMO energy levels. Significantly, compared to C 60 , the reductions of the [6,6]-bridged derivative 2 as well as of the doubly [5,6]-bridged compound 5 occur at more negative potentials, whereas those of the singly [5,6]-bridged compounds 1, 3, 4 are found at less negative potentials.