Inclusion carborane

Figure 4.35 Chloride inclusion within the carborane-based mercura[12]crown-4.

The a- and P-phases of CTV both contain guests but the guests do not reside in the saucer-shaped cavity. More recent reports of a y-phase and exotic inclusion compounds with C60 and carboranes as well as network structure show that they CTV cavity does include guests, however. 

Whilst it is very encouraging that our recent work with metallacarborane isomerization has provided experimental support for the conclusions of previous theoretical studies on carborane isomerization, the inclusion of metal vertices can clearly have a moderating effect. This is dramatically demonstrated by examples of metal-dependency. Thus, reaction of 3 with Pt(PR3)2 " instantaneously produces a 1,2 1,7 Ccage isomerization, whereas reaction with Ni(PR3)2 " results in one... 

An interesting example of the interplay between solid-state clathrands and solution-phase cavitands is provided by cyclotriveratrylene (CTV, 8). In the solid state, the saucer-shaped CTV molecules stack one on top of another in the two most common phases (x and and hence, while the molecules possess shallow molecular cavities, they do not include guests such as solvent molecules, which instead are located in voids between host stacks. However, larger guests such as buckminsterfuller-ene C6o, organometallic sandwich compounds,or carboranes form intracavity inclusion compounds, and the association persists in the solid state, with potential applications, for example, in the selective purification of fullerenes. Thus, CTV is both a cavitand and a clathrand. The cavitand behavior of CTV is highlighted by the chemistry of the double-CTV cryptophanes that form very stable solution complexes with a variety of halocarbon guests. 

Figure 2 X-Ray structures of inclusion motifs in crystalline CTVs. (a) A misaligned stack of a-phase CTV (b) intracavity complexation of 1,1,1-trichloroethane (c) baU-and-socket structure from the complex (o-carborane)(CTV)2 hydrogen bonds between the acidic carborane C-H and CTV are indicated as dashed lines (d) hand-shake motif in 6. (e) Solvent-filled channel in clathrate complex of 7, where self-inclusion and tt-tt stacking interactions result in an open structure.

Among the solid state structures of the larger calix[ ]arenes, Raston [96] and coworkers reported the first inclusion complex of p-tert-butylcalix[9]arene C[9] with o-carborane (Fig. 7.30). In this structure, the calix[9]arene macrocycle adopts a conformation composed by three 3/4-cone clefts and a pleated-loop portion. Perrin et al. [97] showed that p-tert-butylcalix[10]arene C[10] adopts in the solid state a pinched cone conformation stabilized by a circular H-bond between OH groups and very similar to that found for calix[6]arene macrocycle [98]. 

The t-butyl-calix[9]arene co-crystaUizes with o-carborane, cyclohexane and water. It does not form inclusion complexes with either of these compounds. The conformation of the calixarene is basically similar to the rosette one but it is highly folded (Fig. 38.30a). In case of the t-butyl-calix[10]arene inclusion of one acetone and one toluene molecule inside the macrocyclic ring occurs and two other toluene molecules take part in additive complex formation (Fig. 38.30b). In this... 

Most of the carboranes known belong to a series of general formula B C2H 2 5 examples with values of n from 3 to 10 inclusive are known. Several monocarba-derivatives have also been prepared, generally as anions B CH i both series are isoelectronic with borane anions B H , and have closed cage structures with no bridging hydrogens. 

A rod-shaped moleeular motor consisting of a p-terphenyl shaft attached to p-carborane (162), whose antipodal position carries a dipolar 2,3-dichlorophenyl rotator, forms an inclusion compound with hexagonal tris-o-phenylenediojgrcyclotriphosphazene (TPP) (163). Based on solid-state NMR, X-ray powder diffraction, dielectric loss spectroscopy and DFT, it is concluded that the whole molecule inserts into TPP channels. However, the sample does not exhibit collective behaviour even at 7 K presumably due to the large harrier to rotation. ... 

The major advantage of our approach is that the desirable features of inorganics and organics such as high thermal and oxidative stability and processability are incorporated into the same polymeric chain. The siloxane units provide thermal and chain flexibility to polymeric materials. Siloxane-acetylenic polymers have also been made but lack the thermal and oxidative stability that the carborane units possess. The chemistry involved in synthesizing poly(siloxane) and poly(carborane-siloxane) has been modified to accommodate the inclusion of an acetylenic unit in the backbone. The novel linear... 

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