Supercage of Y zeolites

Xenon atom, with a diameter of 4.41, can only migrate into the supercages but not the sodalite or D6R cavities. Various investigations [4-6] shoved that Xe NMR is a sensitive probe for the geometric and electronic enviroments inside supercages of Y zeolites ... 

Figure 7 Scheme for intramolecular photocycloaddition of N-P -N within the supercage of Y-zeolite. 

Jiang Y X, Sun S G, Ding N, Novel phenomenon of enhancement of IR absorption of CO adsorbed on nanoparticles of Pd confined in supercages of Y-zeolite, Chem. Phys. Lett., 344 (2001) pp. 463-470. 

The zeolite cavities can be considered as peculiar reaction nanovessels where the chemical processes carried out inside them and their products are affected by the confines in which they are being performed. This main principle was proven in mid-70 s when the first synthesis of neutral phthalocyanine complexes encapsulated in Y zeolites via intracrystalline assembling was performed at Moscow State University [1,2]. Once formed within the bottle-shaped supercages of Y zeolite, the resulting electroneutral complexes cannon leave them because of spacial restrictions. Later, this new type of inclusion compounds was termed as "ship-in-a-bottle" systems [3]. 

Several studies using Xe to probe well-known materials in order to gain additional information have also been recently published. Fraissard and coworkers " have used xenon-131 NMR to characterize the electric field gradients inside the supercages of Y zeolites. Composite pulses were used in the nutation experiments to... 

Lunsford et al. [ 119,120] and Verdonck et al. [ 121 ] were the first to define the best treatment conditions to obtain small ruthenium clusters in the supercages of Y zeolites. Ion exchange was carried out in aqueous solutions of [RufNHjig] CI3. 

As mentioned in Section II, each supercage of Y-type zeolite can include five molecules of benzene, two molecules of naphthalene, or two molecules of pyrene [70-75]. Thus, one might expect that both aryl parts of a molecule with a, -diaryl groups separated by a flexible chain can be included in one supercage, and the in-... 

The photolyses of conformationally fixed 3,y-unsaturated ketones can also be performed in constrained media. This was described for the ODPM rearrangement of bicyclo[2.2.1]heptenone and bicyclo[2.2.2]octenone in MY zeolites [47]. It is remarkable that direct irradiation of the guest-incorporated thallium-Y (TIY) zeolites at 254 nm resulted in higher yields of ODPM products than the triplet-sensitized solution photolyses (Sch. 19). This indicates that the triplet carbonyl species are generated more efficiently in the supercages of the zeolites presumably because of the presence of heavy... 

The chemistry fo Ruthenium in Y zeolites has been extensively investigated (5), and seems to parallel in many respects its behavior in homogeneous media. More particularly, the chemistry of Ru(III)(NH3) in the supercages of Y-type zeolites has reciev-ed considerable attention (1,6-IQ), either in vacuum, inert atmosphere, or in presence of 02, CO and NO. 

In a variation on this theme, a bulky guanidine derivative, N,N,N"-tricyclohex-ylguanidine was encapsulated by assembly within the supercages of hydrophobic zeolite Y. The resulting ship-in-a-bottle catalyst was active in the aldol reaction of... 

NaY, KY, RbY, and CsY zeolites efficiently produced the corresponding trans isomers 21b-d. In sharp contrast to the very low des (0-5%) obtained upon irradiation of 20b-d in isotropic dichloromethane/hexane solutions, photolyses of the same substrates in zeolites gave much improved des of up to 55% for 21b in NaY. The de of 21b critically depends on the countercation of Y zeolite, affording 50% for LiY, 55% for NaY, 30% for KY, 22% for RbY, and 5% for CsY. In LiY 1-phenylethyl amide 20d afforded 21b in de as high as 80%. Ramamurthy emphasized the importance of the cation-substrate interaction within the supercage for controlling the diastereodifferentiating photoreaction [69,70]. 

A catalytic center can be created in a zeolite cage by the incorporation of a transition metal compoimd, e.g. ferrocene, [Fe(CsH5)2], which may be the catalyst or the precursor. To assess the strength of the interaction between the encapsulated ferrocene and the zeolite the INS spectrum of ferrocene in the supercage of potassium zeolite Y has been compared with the INS of solid ferrocene [122]. The spectra are shown in Fig. 7.29 and the assignments, according to the INS and computed spectrum of solid ferrocene [123] in Table 7.20. 

Various types of NMR experiments have previously been performed on the cations of Y zeolites. The work of Basler (9) on hydrated Y zeolites is particularly relevant. Performing static sodium-23 NMR measurements at 16 MHz, he observed a single NMR line which disappeared as he exchanged in increasing amounts of calcium. He concluded that sodium in the supercage was being preferentially removed, and that sodium in the Type I and I sites was unobservable at such a low frequency, due to quadrupolar interactions. In order to use the sodium-23 NMR spectra of Figures 2 and 4 to determine how... 

One of the most elegant synthetic approaches to using the internal cavities of zeolites as nanometre size reactors is that of the ship-in-a-bottle synthesis of metal complexes within zeolite cages, which are then too large to escape through the cage windows. The term was initially coined by Herron to describe metal complexes, such as those with salen-(bis(salicylidene)ethylendiamine-) " or phthalocyanine (Scheme 6.9) that were formed in the supercages of faujasitic zeolites. Zeolites X and Y are most commonly used, but the fully... 

Ozin, Ozkar, et ai. [226-229] reported a new approach to synthesizing transition metal oxide structures in molecular sieve hosts. [W(CO)6] located within the supercages of NaY zeolite was photochemically dissociated in the presence of O2. This method provides a mild and quantitative synthetic pathway to tungsten(VI) oxide moieties which are encapsulated within the supercages of the zeolite Y (Eq. 4.19). 

In 1970, Yishima and co-workers focused attention on the distribution of xylene isomers produced by alkylation of toluene with methanol over a variety qf cation-exchanged Y-zeolites. The relatively high amount of para isomers (45 — 50% selectivity) was obtained with certain catalysts. They attributed this to the preferential formation of para isomer and the suppression of the isomerization of the para isomer thus formed in the supercage of the zeolites. 

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