H-cage

The discovery (116) of the base-promoted degradation of the isomeric f/ojo-CjB H cages provided one of the most important carborane anion systems, the isomeric [m/<9-C2B9H12] anions,... 

Table 10 Calculated characteristics of the C2H2 and BNH2 molecules in the isolated state and encapsulated into the C70 (D h) cage [33]... 

TABLE 23. Calculated bond distances (pm) in M H cage compounds"... 

As in the case of monocyclic 3- and 4-MRs (see Section V.E.l.a.ii), electropositive substituents stabilize also M H cage systems which include such rings, e.g. tetrahedranes, prismanes and cubanes (Table 24)191,192,195. The only isolated tetrasilatetrahedrane indeed carries the electropositive Si(Bu-t)3 groups as substituents238. Nevertheless, the steric protection afforded by the bulky silyl ligands is probably the most important factor allowing the isolation of the tetrasilatetrahedrane179 195. 

With the existence of THF, H2 can be enclathrated in the hydrate cages depending on the composition of gas mixtures. In the H2 + CO2 + THF mixed hydrate, it is likely that THF occupies all of the H-cage while H2 and CO2 can occupy the D-cage of s-ll hydrate competitively. 

Situation (9.84a) involves external P atoms linked directly to the B/H cage, while (9.84b) represents replacement of some B atoms in the original cage by P atoms. In both cases B-P linkages are present. 

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