Hexameric cage structures

The most frequent structures of organo-alumoxanes are hexameric cage structures (41-45) [67] (Figure 3.5-11) (Table 3.5-3). The Al O core can be described as a drum-like hexagonal prism with alternating A1 and O atoms. The AI3O3 hexago-... 

Recent studies have shown that the bowl-shaped C-alkyl substituted pyrogal-lol[4]arene macrocycles readily self-assemble to form a gobular hexameric cage, which is structurally robust and remains stable even in aqueous media (Fig. 20.4.38). Slow evaporation of a solution of C-heptylpyrogallol[4]arene in ethyl acetate gives crystalline [(C-heptylpyrogallol[4]arene)6(EtOAc)6... 

A different neutral hexameric coordination cage structure was assembled from six either C-propyl- or C-pentyl-pyrogallol[4]arene units and 12 Ga(III) ions [51]. In both cases the centroids of the macrocyclic ligand components reside on the vertices of a squeezed octahedron enclosing a space of approximately 1150 A3. Only a total of 20... 

Figure 20. Hexameric lithium arenethiolates. (n) Planar Li Sh 12-membered ring structure, (b) Li,S cage structure.

Some methylzinc thiolates with bulky groups on the sulfur form self-assembled aggregates with cage structures and four-coordinate zinc. Thus, the /crt-butyl derivative is a pentamer, [MeZnSBu js, 16, (in benzene solution) [33] and the isopropyl derivative is an octamer, [MeZnSPr jg, 17 [34]. According to cryoscopic measurements [4] the latter is hexameric in benzene solution, indicating facile interconversion between variously aggregated (supramolecular) forms. 

By using the ammonium ions with four alkyl groups larger than the methyl group, the other types of silicate anions with cage-like structures are formed. For example, in tetraethylammonium (N+(C2H3) ) silicate aqueous solutions, the prismatic hexameric silicate anion (SigO g, prismatic hexamer) is formed (13,14,17,18). 

Simple examples of cyclic oligomers formed through ionic interactions are the trimer of lithium bis(trimethylsilyl)amide, [LiN(SiMe3)2]3 (Scheme 13), " and hexameric [LilSCeHs (CH2NMe2)2-2,6 ]6 More intricate cage, ladder, and other polycyclic structures are formed in various other compounds. " ... 

ABSTRACT. The title hexaphenol (1), a direct analogue of the 3 hydro-quinone hexameric unit, has been prepared by six-fold demethylation of hexakis( -methoxyphenyloxy)benzene (2) with BBrs. Host forms a trigonal adduct, space group R3, = 22.088(3), = 12.232(3) A, containing 6 molecules of pyridine per host molecule a detailed X-ray study of this inclusion compound reveals a true clathrate structure, the closed cages of which accommodate a small, non-stoichiometric amoupt of water.. ... ... 

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