Cage molecules

Nagase S, Kobayashi K and Akasaka T 1996 Endohedral metallofullerenes new spherical cage molecules with interesting properties Bull. Chem. Soc. Japan 69 2131-42... 

Many highly strained cage molecules undergo rearrangement when treated with metallic ions such as Ag , Rh(I), or Pd(II). The bond rearrangements observed can be formally classified into two main types (1) [2 + 2] ring... 

There is an interesting tendency of the ring strains of the large cage molecules. Persiladodecahedrane Sij Hj (SE = 32.3 kcal mol ) is less strained than the carbon congener, dodecahedron (SE = 43.6 kcal mol ) [76, 77]. Low strain of silicon congener is more apparent for persilafulleran (SE =114 kcal... 

Molecules such as P4 and the polyanionic clusters such as Si4- or As2- that are discussed in Section 13.2 are representatives of electron precise closo clusters. Organic cage molecules like tetrahedrane (C4R4), prismane (C6H6), cubane (C8H8), and dodecahedrane (C20H20) also belong to this kind of cluster. 

The dispiro compound A reacts with 2 cage molecules B to form the complex molecule 77 displayed in Fig. 13. The intermediate in brackets cannot be isolated. In contrast to the reaction of the same stannylene with sulfur (Eq. (26)) the dispiro compound A cannot be isolated seperately. The mechanism of reaction (34) may of course be more complicated. The cage molecule B is discussed in more detail in Section 6.5. It should be noted that in 77 six tin atoms of two different oxidation states are combined. 

Reactions of selected metal complexes of multidentate amines with formaldehyde and a range of carbon acids (such as nitroethane) have led to ring-closure reactions to yield a series of three-dimensional cage molecules (see Chapter 3). Condensations of this type may also be used to produce two-dimensional macrocycles (Comba et al., 1986) - see [2.20], In such cases, it appears that imine intermediates are initially produced by condensation of the amines with formaldehyde as in the Curtis reaction. This is followed by attack of the conjugate base of the carbon acid on an imine carbon. The resulting bound (new) carbon acid then reacts with a second imine in a cis site to yield chelate ring formation. 

Fig. 6), which can be used as a bridgehead scaffold for the all-carbon cage molecule Q-C6o (42), an isomer of Ih-buckminsterfullerene that is 767 kcal-mol 1 higher in energy by the calculated heats of formation (RHF/3-21G).110,291 A similar macrocyde (45, C6oH6) of easier synthetic accessibility is based on the 1,3,5-triethynylbenzene moiety. 

Another, more recent, fluorine contribution to the development of new branches of chemical science is connected with fullerenes, the first members of this family of close-caged molecules being obtained only about a decade ago. Fullerenes, having the composition C , C70, C76, C84.. . , represent the new... 

All attempts to bond R3P7 as a ligand to metal(O) complexes have failed. In contrast, the preparation of complexes with the related cage-molecules Pi (Sime2)3 was successful (8 ). 

Some examples of nitrate ester incorporation into caged molecules have been reported 1,3,5,7-tetranitroxyadamantane (97) has been synthesized in three steps from 1,3,5,7-tetrabromoadamantane (96) and 1,4-dinitroxycubane (99) ° has been synthesized from the nitration of the corresponding diol (98). 

Marchand, A.P. 1988. Synthesis and chemistry of novel polynitropolycyclic cage molecules. Tetrahedron 44 2377-95. 

Fascinating macrocyclic receptor cages based on a triaza-18-crown-6 derivative (79) and on a rigid cyclotriveratiylene unit (188) can be synthesized (189) by cormecting the two residues via three bridges in a single step. Macropolycycles, such as ( )-193 have been reported (189), and since the cyclotrivera-trylene unit is chiral and has been resolved (188), the preparation of optically active macrocyclic receptor cage molecules should be feasible (see below). 

One key conclusion is that the entire molecule must be taken into account to understand the aromatic properties of icosahedral fullerenes. The 2(N -1-1) rule of spherical aromaticity also sufficiently describes the magnetic behavior of non-icosahedral fullerenes [128], homoaromatic cage molecules [129], and inorganic cage molecules [130],... 

Fig. 1 Examples of polyhedral cage molecules and metalloid clusters (first row) compared to related Zintl ions and intermetalloid clusters that are obtained from the reaction of Zintl ions (second row)...

In this chapter, the chemistry and the structures of Zintl ions and cage molecules are summarized and put in the context of intermetalloid clusters. The emphasis is put on the observation that irrespective of the starting material (Zintl ions or small low-valent organometallic compounds) the same types of intermetalloid clusters are formed. 

All other homoatomic Pn cluster anions are cage molecules with localized two-center-two-electron bonds. The cyclic [PnJ anion has been characterized by NMR spectroscopy for Pn = P [210], and structures are known for Pn = P, As, Sb, Bi (Table 2). A planar [Ps] anion has only been detected in solution by P NMR spectroscopy [210]. Envelop-shaped five- and six-membered rings are found for [Pns] and [Pe]", whereas [Asg]" deviates only slightly from planarity and has a chair conformation. The aromaticity of the planar anions [P4] and [Pe]" is distinct from that of regular 671-aromatic hydrocarbons and has been described... 

Furthermore, evident stmctural similarities between compounds obtained through reaction with Zintl ion clusters and ligand-stabilized cage molecules occur (Table 11). 

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