Fullerene hydrogenation

In textbooks of fullerene chemistry, hydrogenation is the simplest reaction and fullerene hydrides are the simplest derivatives of fullerenes. Hydrogenation can be conducted under pressure and elevated temperatures. Heating at 400°C and 80 atm H yields red solid, [40]. Up to 48 H atoms can be added to under more forcing conditions. Catalytic hydrogenation at 280°C and 160 atm with use of Ru/C catalyst produce hydrofulerenes up to [41]. Hydrogenation is quite... 

So far, direct evidence of C60 hydrogenation inside of nanotubes from HRTEM imaging is absent. It is required as a decisive demonstration of possibility for hydrogen to penetrate inside of peapods but could possibly be challenging experimentally. Chemical reaction within nanospace of carbon nanotubes is possibly only first example of interesting nanoscale chemistry and fullerene hydrogenation in other exotic environments will possibly be successfully demonstrated in future. It is quite likely that hydrogenation in confined space results in formation of fulleranes with different molecular structures. 

Table 6.1 [60]Fullerene hydrogenation reactions leading to C3v CM II 8 run in neat, boiling diethylenetriamine (DETA) under N, in the dark ...

Abstract NMR spectroscopy is so far the only analytical technique that has been used to get a detailed structural characterization of hydrogenated fullerenes. A substantial amount of information derived from different NMR experiments can thus be found in the literature for a number of fullerenes hydrogenated to various degrees. These studies have benefitted from the fact that chemical shifts of II and 13C and in some cases also 3He can be used to obtain structural information of these compounds. Such results, together with discussions about different NMR experiments and general considerations regarding sample preparations, are summarized in this chapter. The unique information, both structural and physicochemical, that can be derived from different NMR experiments ensures that this technique will continue to be of central importance in characterization of hydrogenated fullerenes. 

It might be well to point out also that at sufficiently low temperatures the curves of (t) dependences are more steep, but their slope decreases with increase in temperature and c (t) curves become comparatively flat. By this is meant that at rather high temperatures, when the c", (t) dependence is more low, the fullerenated hydrogen may appear, i.e., a set of hydrofiillerenes with different hydrogen content is formed, as revealed also experimentally [39],... 

Figure 2-100. CORINA-generated 3D molecular model of a fullerene dendrlmer with 1278 atoms (762 non-hydrogen atoms).

The H C ratio in hydrocarbons is indicative of the hydrogen deficiency of the system. As mentioned, the highest theoretical H C ratio possible for hydrocarbon is 4 (in CH4), although in electron-deficient carbocationic compounds such as CH5 and even CH/, the ratio is further increased (to 5 and 6, respectively, see Chapter 10). On the other end of the scale in extreme cases, such as the dihydro- or methylene derivatives of recently discovered Cgo and C70 fullerenes, the H C ratio can be as low as 0.03. 

It is also important to point out that pure cobalt oxide, alone or finely dispersed in Si02 (i.e. Co-Si02, Co-Si02-l and Co-Si02-2 in Table 1), zeolite HY, fullerene (i.e. C q/C-,0 80/20) is at least as effective as the reduced oxides for the production of nanotubules in our experimental conditions. In fact, the catalysts studied in this work are also active if the hydrogenation step is not performed. This important point, is presently being investigated in our laboratory in order to elucidate the nature of the active catalyst (probably a metal carbide) for the production of nanotubules. 

The formation of fullerenes and CNTs has also been affected by their environmental atmosphere [22] and, in particular, a hydrogen atmosphere plays an important role in forming graphitic structures of multi-walled CNTs (MWCNTs) in the form of buckybundles [24]. Intercalation into MWCNTs has been difficult or impossible, because there is no space for intercalants to enter into a Russian-doll-type structure of the nanotubes. However, the buckybundles formed in the hydrogen arc discharge were found to be successfully intercalated with potassium and ferric chloride (FeCl3) without breaking the... 

This paper is concerned with the structures of the simplest possible adducts of the Ceo and C70 fullerenes, namely the monohydrides, CmH and C H. These open shell species or radicals may be considered as the product of the addition of one atom of hydrogen or one of its isotopes, among which we include specifically the light pseudoisotope of hydrogen known as muonium. Mu = pfe. Although Ceo//has been observed [1], the stimulus for these calculations arose from the experiments on muon implantation in solid [2,3] and C70 [4]. 

Ceo and higher fullerenes are distinguished from other allotropes of carbon, diamond and graphite, in that they exist as discrete molecules. The spherical or ellipsoidal nature of the monotropes opens up the possibility of intriguing new areas of chemistry. Here we are only interested in the hydrogen (or muonium) adducts, although this study has important implications to the very vigorous and extensive research in fullerene chemistry. 

Chen, J. and F. Wu, Review of hydrogen storage in inorganic fullerene-like nanotubes. Appl. Phys. A, 78, 989-994, 2004. 

T. Jarrosson, G.-W. Wang, M. D. Bartberger, G. Schick, M. Saunders, R. J. Cross, K. N. Hock, Y. Rubin, Insertion of Helium and Molecular Hydrogen Inside an Open Fullerene , manuscript in preparation. 

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