Adamantane-like unit

Figure 20.4.5 shows the crystal structure of [Cu l,4-C6H4(CN)2 2]BF4. The nodes are the four-connected Cu atoms, each being coordinated tetrahedrally by N=C-C6H4-C=N ligands as rods. The adamantane-like structure unit is shown in Fig. 20.4.5(a), and repetition of such units along a twofold axis leads to fivefold interpenetration. The remaining space is filled by the BF ions. 

Left) Two interpenetrating networks in the crystal structure of ice-VII. (Right) Two views of an adamantane-like structural unit. 

The ternary Cu4SnPio with an unusual Sn Cu3 unit is the only compound with the adamantane-like Pio cage. This is remarkable, because in that region of composition some... 

Other molecules that contain four key aromatic units arranged in a tetrahedral array, do not necessarily have Td symmetry. Distortion creates two groups of lower symmetric structures, D2d and Qv Two examples of what stem from D2d symmetry are the adamantane-like macrotricycle (119, R=C6H13), synthesized by Moore and Wu [160], and Tani et al. s cross-oriented biphenylophane (120) [134] obtained with its parallel polycyclic isomer (99). 

The molecular structures of 10 and 11 were deduced by X-ray diffraction (Fig. 5). Compound 10 contains an AlsNBSiNs and 11 an AlaNaSiOa structural unit, both exhibiting an adamantane-like structure. 

Figure 2. (a) An adamantane-like component of the diamond net showing one of the 2-fold axes, (b) View of adamantane unit looking slightly offset from the 2-fold axis. 

More recently, and based on the same concept, O Neill and coworkers have prepared a series of related systems (80a-c) based on Vennerstrom s adamantyl trioxolane unit". These derivatives, which are synthesized in only three steps from adamantan-2-one, have activity in the low nanomolar region (<3 nM versus K1 P. falciparum). Like the prototypes synthesized by the groups of Meunier" and Singh", these compounds can be formulated as water-soluble salts and it is anticipated that these agents may have the capacity to hit the parasite by two distinctive mechanisms. Indeed, any chemical or metabolic degradation of the endoperoxide bridge in these compounds will result in metabolites that may still have the ability to function as inhibitors of heme polymerization provided that they do not become covalently attached to proteins in the bioactivation process. 

Figure 4. (a) Two interpenetrating adamantane units in the structure of Zn(CN)2. Circles represent Zn and connections between Zn atoms are provided by linear bridging cyanides, (b) A single cyclohexane-like Zn6(CN)6 ring catenated by six distinguishable rings. 

Some carboranes have formulae compatible with both classically bonded and nonclassically bonded structures and exhibit valence isomerism. The tet-racarbaborane Me4C4B6Et6 is one such. As prepared by dimerization of the small closo carborane Me2C2B3Et3 [Eq. (3.2)], it has a classical adamantane-type structure, with its four CMe units linked through BEt units (1). However, when heated it isomerizes to the expected nido carborane structure (2) with a skeletal structure like that of decaborane. ... 

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