Endohedral cluster

Metal-carbide clusters are relevant to the fonnation of both endohedral fullerenes and carbon nanotubes [1351. There also exists a class of apparently stable metal-carbide cluster ions, = Ti, V, Cr, Zr and Hf), called... 

T. Fassler, S. D. Hoffmann, Endohedral Zintl ions intermetallic clusters. Angew. Chem. Int. Ed. 43 (2004) 6242. 

So far, three types of i-QCs appear in the literature Mackay [17], Bergman [18], and Tsai types [19], which have been differentiated on the basis of the polyhedral cluster sequences observed in the respective 1/1 AC structures. These are commonly represented as shown in Fig. 2. An i-QC is concluded to be Mackay-type if its 1/1 AC contains a 54-atom multiply endohedral cluster ordered, from the center out, as a small icosahedron (12 atoms), a larger icosahedron (12), and an icosidodecahe-dron (30). This motif occurs in ACs that consist of transition metals and main-group elements on the right side of the periodic table such as Al-(Pd,Mn)-Si [17,20]. In... 

Fig. 2 Schematics of the multiply endohedral clusters in Mackay-, Bergman-, and Tsai-type 1/1 ACs...

Two other well defined carboranes 55g and 76 (vide infra, Section 3.2.7) are present in the reaction mixture containing 64c (vide infra, Scheme 3.2-35). Although pure 55g could not be isolated, its solution-state structure follows from a complete set of NMR spectra [71b], This unusual carborane is a spiro derivative without precedence and belongs to the family of 2,3,5-tricarba-mdo-hexaboranes(7). Ab initio MO calculations and NMR data indicate that the boron atom linked to the C3B3-framework by an endohedral C-B bond takes part in the cluster bonding [71b] (similar to an endohedral C-H bond in the other carboranes 55). 

Diener MD, Bolskar RD, Alford JM (2002) Redox properties and purification of endohedral metallofullerenes. In Akasaka T, Nagase S (eds.) Endofullerenes a new family of carbon clusters. Kluwer, Dordrecht, pp. 133-151. 

Fullerene generation by vaporization of graphite or by combustion of hydrocarbons is very effective and certainly unbeatable what facile production in large quantities is concerned. However, total synthesis approaches are attractive because (a) specific fullerenes could be made selectively and exclusively, (b) new endohedral fullerenes could be formed, (c) heterofullerenes and (d) other cluster modified fullerenes could be generated using related synthesis protocols. 

Wang JQ, Stegmaier S, Wahl B et al (2010) Step-by-step synthesis of the endohedral stannas-pherene Ir Sni2 via the capped cluster anion Snglrlcod) I Chem A Eur J 16 1793-1798... 

The electrochemical properties of TNT-EMFs, M3N C2n n > 39) differ from those of the empty cage fullerenes (see Fig. 6) due to the interaction of the metal cluster with the carbon cage and because the structure of these carbon cages are generally different. As a consequence, the reductive processes are electrochemically irreversible but chemically reversible. The oxidative processes occur at lower potentials because the HOMO orbital is mainly localized on the trimetallic nitride clusters and the HOMO-LUMO gaps in solution are smaller [25,58]. The endohedral metallo-fullerenes M C2n show similar behavior but even smaller HOMO-LUMO gaps [59]. 

Chaur MN, Melin F, Ortiz AL et al (2009) Chemical, electrochemical, and structural properties of endohedral metallofullerenes. Angew Chem Int Ed 48 7514-7538 Stevenson S, Mackey MA, Stuart MA et al (2008) A distorted tetrahedral metal oxide cluster inside an icosahedral carbon cage, synthesis, isolation, and structural characterization of Sc4(p3-O)2 lh-Cgo. J Am Chem Soc 130 11844-11845... 

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