Hydride encapsulation

Hydride encapsulation in inverse crown molecules has also been observed. The reaction of NaBu, MgBu2 and three equivalents of HNPr 2 led to [Na2Mg2(NPr 2)4(p-H)2] " which... 

Silicon—Ca.rbon Thermoset. The Sycar resins of Hercules are sihcon—carbon thermosets cured through the hydrosilation of sihcon hydride and sihcon vinyl groups with a trace amount of platinum catalyst. The material is a fast-cure system (<15 min at 180°C) and shows low moisture absorption that outperforms conventional thermosets such as polyimides and epoxies. Furthermore, the Sycar material provides excellent mechanical and physical properties used in printed wiring board (PWB) laminates and encapsulants such as flow coatable or glob-top coating of chip-on-board type apphcations. 

Carbonyl hydrides and carbonylate anions are obtained by reducing neutral carbonyls, as mentioned above, and in addition to mononuclear metal anions, anionic species of very high nuclearity have been obtained, often by thermolysis. These are especially numerous for Rh and in certain Rh, Rh and Rhi5 anions have structures conveniently visualized either as polyhedra encapsulating further metal atoms, or alternatively as arrays of metal atoms forming portions of hexagonal close packed or body... 

Several triphenylgermanium hydrides have been prepared where the hydride atom is encapsulated by substituents on the phenyl ligands,95,108-111 as illustrated in Equations (84)-(86).110,111 The germanium atom of 42a-c are formally hexacoordinate and that of 43 is heptacoordinate. A tribenzobarellenegermane compound with a trihydro-germane moiety attached to the bridgehead carbon was prepared and characterized (Equation (87)), and this species was found to be exceptionally air stable.1... 

M. J. McCollum and G. E. Stillman, High Purity InP Grown by Hydride Vapor Phase Epitaxy T. Inada and T. Fukuda, Direct Synthesis and Growth of Indium Phosphide by the Liquid Phosphorous Encapsulated Czochralski Method O. Oda, K. Katagiri, K. Shinohara, S. Katsura, Y. Takahashi, K. Kainosho, K. Kohiro, and R. Hirano, InP Crystal Growth, Substrate Preparation and Evaluation... 

Thicker sections can be cross-linked by hydrosilylation addition. This is the same chemistry used to produce fluorosilicone monomers with the vinyl functionality present on silicon. The catalyst reaction occurs between a vinyl group and silicone hydride.66 The advantage of this system is that it does not produce volatile by-products. On the other hand, the disadvantage is that it is available only as a two-part system.67 Recently, however, one-part, platinum-catalyzed products have been developed.66 The reaction is very rapid and at room temperature it is completed in 10 to 30 minutes. It is accelerated with increasing temperature and at 150°C (302°F) it is completed within a few seconds. This makes the compounds ideal for fast automated injection molding operations.68 One-part systems use the chemical complexing of the catalyst, which is activated at elevated temperatures, or its encapsulation into an impermeable shell, which is solid at room temperature and melts at elevated temperatures68... 

Modification of zeolites, based on chemisorption of silane or diborane and subsequent hydrolysis of the chemisorbed hydride groups can also be applied for encapsulating gas molecules in zeolites. For example, krypton and xenon can be encapsulated in mordenite combining the modification process with a physical adsorption of the noble gases at moderate pressures and temperatures (e.g. 100 kPa, 300 K). The encapsulates are homogeneous and stable towards acids, mechanical grinding and y-irradiation. By controlling the pore size reduction however, the thermal stability can be controlled. 

To increase thermal conductivity of powder layer metal powders of copper, aluminium are added. Composites are compacted in pellets, which can be sintered in addition. Their main characteristics are coefficient of effective thermal conductivity and coefficient of gas-permeability. The weight fraction of powder in such compacts serves as the controlled parameter, and it has the optimum, when gas-permeability does not worsen sharply at acceptable thermal conductivity. Encapsulation of hydride powder by material with high thermal conductivity followed by compaction of pellets and their sintering is also used. 

Further studies on the supramolecular coordination chemistry of copper(II) focused on the synthesis of oligonuclear complexes by self-assembly with the pentadentate ligand (L3)2 with 2,6-pyridinyl-spacer [70]. To this end, H2L3 (4) was treated with calcium hydride and copper(II) acetate to give the metallocoronate [(Cac Cu2(L3)2 )(OAc)2] (5 Scheme 2). In the crystal, 5 is present as a dinuclear copper(II) coronate in which a calcium ion is encapsulated in the center two acetates act as counterions. 

When triethanolamine H3L13 (35) was reacted with sodium hydride and iron(III) chloride, the hexanuclear centrosymmetric ferric wheel [Nac Fe6(L13)6 )Cl (36) was isolated. Amidst a set of possibilities in the template-mediated self-assembly of a supramolecular system, the one combination of building blocks is realized that leads to the best receptor for the substrate [112]. Therefore, the six-membered cyclic structure 36 is exclusively selected from all the possible iron triethoxyamine oligomers, when sodium ions are present. The iron(III) complex 36 is present as an Sg-symmetric wheel, with an encapsulated sodium ion in the center and a chloride counterion. Consequently, the trianion (L13)3- acts as a tripodal, tetradentate, tetratopic ligand, which each links three iron(III) ions and one sodium ion. In the presence of cations with different ionic radii, different structures are expected. Therefore, when triethanolamine H3L13 (35) was reacted with cesium carbonate and iron(III) chloride, the octanuclear centrosymmetric ferric wheel [Csc Fe8(L13)8 ]Cl (37) was isolated (Scheme 13) [113]. 

Container design is most important. To completely avoid the expansion problem we have developed an encapsulation scheme shown schematically in Figure 5(11,12). The expansion is accommodated by the loosely packed individual capsules, preventing any stress on the main container walls. Each capsule is a thin-walled A1 tube containing the hydride and capped on one or both ends with a porous metal filter. Such a design also eliminates the long distance gas impedance problem of a packed bed. 

Figure 5. Encapsulation of hydride to prevent expansion and packing problems 1 = Al capsule 2 = flute 3 = porous filter 4 = hydride.

Particulate materials which have been studied in the encapsulation process include sodium chloride, sodium dichromate, lithium, sodium, lithium hydride, zinc, and lithium aluminum hydride. Typical experiments are described below. 

Example 1 Encapsulation of Lithium Aluminum Hydride with Poly(chloro-p-xylylene). In the distillation zone were placed 5.0 grams of dichloro-di-p-xylylene. In a 4-oz. polyethylene bottle were placed 10.0 grams (400 pellets) of lithium aluminum hydride (LAH). LAH was obtained from Metal Hydrides, Inc., as 1/8-inch diameter pellets. The bottle was positioned in the coating chamber, the system was... 

Attention was then turned to encapsulation of a more reactive species, lithium aluminum hydride (Example 1). Several batches were encapsulated readily with poly (chloro-p-xylylene) utilizing the standard tumbling process. Products with from 1-20 wt. % coating were prepared. 

In rhodium clusters, e.g., [Rh13(CO)14H5. ]" (n = 2 and 3), only one of the H atoms is encapsulated and 3H nmr spectra show that this atom interacts with all 13 Rh atoms (103Rh, spin V2) and is thus migrating within the cluster. Proton transfer reactions of interstitial hydrides have been studied72 and more complex hetero-nuclear species73 can be made by reactions such as... 

Inverse Sodium Hydride , a crystalline salt that contains the reverse H+ and Na formed by reversible encapsulation of H+ in 3 adamanzane (Adz), has been synthesized and characterized. Theoretical studies of the analogous MesN H+- Na suggest that the species is indeed metastable with respect to deprotonation in solvents having dielectric constants below 2. ... 

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