Caged structures cubanes

Adsorption of a condensed 1-hydroxy-adamantane layer at the Hg elec-trode/(Na2S04 or NaF) solution interface has been studied as a function of temperature by Stenina et al. [174]. Later, Stenina etal. [175] have determined adsorption parameters and their temperature dependence for a two-dimensional condensation of adamantanol-1 at a mercury electrode in Na2S04 solutions. They have also studied coadsorption of halide (F , Cl , Br ) anions and 1-adamantanol molecules on Hg electrode [176]. More recently, Stenina etal. [177] have described a new type of an adsorption layer comprising organic molecules of a cage structure condensed at the electrode/solution interface. This phenomenon was discovered for adsorption of cubane derivatives at mercury electrode. 

A relatively large number of tin-nitrogen cage structures have been characterized. The monomeric diazasilastannetidine, SnN(But)Si(Me2)MBu , is cleaved quantitatively by tert-butylamine to give either the closed [Sn2SiN3] cage (108) or the open cage (109). Thermolysis of the latter compound, however, results in conversion to the [Sn. N4] cubane... 

This molecule now has three-, four-, and five-membered rings fused together in a tricyclic cage structure. This is nowhere near the limit for cage molecules. You saw tetra-t-butyl tetrahedrane in Chapter 15, and you will see in Chapter 37 how even molecules such as cubane can be made. 

The dimers have a four-membered A12N2 ring (6-XV) which may have isomers if the groups are different. The aluminum imides [RA1(NR )] usually have cubane or larger cage structures (6-XVI) trimers (e.g., the alumazene 6-XVII) and heptamers have also been found, depending on the size of R and R and the reaction conditions.29... 

Fig.1 Four typical structures of POSS cages a trigonal prismatic (SigOg) cage, b cubane (SisOn) cage, c double five-ring (SiioOis) cage, and d double six-ring (SinOis) cages...

The cubane-like Ge compound [GeN-r-Bu]4 (3) has been obtained as a crystalline sublimable solid by the reaction shown in Scheme l.i The related cage structure of Ge3(N-r-Bu)2(HN-r-Bu)2 consists of a Ge-N cube with one corner vacant this open polycycle can be protonated by HCl to form [Ge3(N-r-Bu)(HN-r-Bu)3]Cl, in which Cl effectively occupies the vacant corner, interacting with the protons on three N atoms of the cube. 

At this point, it is interesting to compare the absence of reactivity of a-halocyclopentanones under Favorskii rearrangement conditions, with the ring contraction observed when such a-halocyclopentanones are included in cage structures used as precursors of cubane derivatives. We will show in what follows that this marked difference in reactivity can be explained by the equatorial stereochemistry of the halogen in the cage a-cyclentanone derivatives. 

In addition to analogs of known C-based structures, transition metals offer novel bonding possibilities having no known precedents in main-group chemistry. As a variation on the cubane-like cage motif of Fig. 4.26(c) built from tetravalent osmium, we can envision construction of the analogous naked metal cage compound Irg... 

The interconnection of two phosphanide substituents by sterically demanding RR Si groups allows the preparation of cage compounds [38], The two-fold lithia-tion of bis(phosphanyl)(alkyl)arylsilane and the dimerization of this bis(phos-phanido)silane leads to the formation of 19 with a strongly distorted Li4P4 hetero-cubane structure according to Eq. (5). 

Structure (5g), with X = SBu1 and MY = ZnMe, is adopted by (MeZnSBut)5,207 formed in the reaction Me2Zn + HSBu This cage can be regarded as an expanded cubane (4w) where the atoms marked Mc, Xc correspond to seven vertices of the cube, but in place of the last M triconnected to the (Xc)3 tripod there is an M—X—M unit connected to two pairs of Xc. 

The iron-selenium cubane-type cluster [Fe4Se4(NO)4] has been shown (52) to adopt a molecular structure of almost exact Td symmetry, whereas in the corresponding anion [Fe4Se4(N0)4] the symmetry is lowered to D2a, just as for the sulfur analogs (37). Upon one-electron reduction the size of the Fe4 cage increases in the neutral molecule the Fe-Fe and Fe-Se distances are 2.703 and 2.342 A, but in the anion the... 

Figure 7. Chem-X model for a (WC>3)4 cubane-cluster encapsulated in an a-cage of zeolite Y, projected down a 3-fold axis of the host structure, displaying tungsten-dioxo anchoring to extraffamework site II Na+ cation six-ring binding sites.

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