Cages acetylenic

The symmetry analysis is consistent with the experimental results reported by Chapman et al. [19]. Photolysis of CBD in an argon matrix produces a pair of caged acetylene molecules that diffuse apart on warming to 35°K. If the matrix is thawed without being irradiated, CBD does not fall apart but dimerizes to syn-tricyclo[4.2.0.0] octa-3,7-diene, as described in Section 7.3.1. 

It is interesting to note that the C-C triple bond character for the acetylenediide inside the silver(l) cages is retained in most of the examples due to the close resemblance of their C=C bond lengths ( 1.09-1.28 A) with that observed in free acetylene (1.205 A).212 The Ag-C bond distances, on the other hand, span a fairly wide range ( 2.01-3.53 A) due to the presence of both a- and 7r-bonding interactions in these systems. The observation of short Ag-Ag contacts of 2.71-3.37A, compared to that in silver metal (2.89 A)213 and the sum of van der Waals radii for silver ( 3.4 A), 1 was suggestive of weak argentophilic interactions associated with these complexes. 

The o-C2Bio cage is readily prepared (Scheme 2.2-2) from acetylene by Lewis base-catalyzed reaction with mdo-decaborane(14) (Bi0Hi4), which is produced in-... 

CARBORANE. A cry stalline compound composed of boron, carbon, and hydrogen. It can be synthesized in various ways, chiefly by the reaction of a borane (penta-or deca-) with acetylene, either at high temperature in the gas phase or in the presence of a Lewis base. Alkylated derivatives have been prepared. Carborancs have different structural and chemical characteristics and should not be conTused with hydrocarbon derivatives or boron hydrides. The predominant structures arc the cage type, the nest type, and the web type, these terms being descriptive of the arrangement of atoms in the crystals. Active research on cargorane chemistry has been conducted under sponsorship of the U.S. Office of Naval Research, http //www.onr.navy.mil/... 

The specifications for the small help gas molecules that fill the small cages of sH hydrate are less rigorous and all guests that adequately fill the small cages in si and sll hydrate are thought to be suitable sH help gas molecules, for example, Ar, O2, Kr, CO, Xe, CH4, H2S, and then to a lesser extent SO2, CO2, CH3CI, and acetylene. CH4, Xe, H2S, H2 have been confirmed to be small sH help gas molecules by structural tools, such as NMR spectroscopy, x-ray, and neutron diffraction. 

Major steps towards the transformation of acetylenic cyclophanes into fullerenes have recently been made by Rubin et al. At the center of their promising approach [28-30] lies a preformed sixty carbon cyclophyne cage which is meant to be brought by appropriate acti-... 

Tobe s group also succeeded in applying the [2+2]cycloreversion process to the formation of smaller carbon cages, notably C36 [40]. Macroscopic quantities of C35 have been produced before [41, 42] and were shown to contain carbon cages that are covalently connected to form polymeric clusters of overall D6h-symmetry. In their efforts to obtain C36 from acetylenic precursors, Tobe et al. prepared cyclophynes 19 and 20 [40]. LD time-of-flight mass spectra of 19 depict a signal for the anion of cyclophyne C3(3H8, generated from 19 by four-fold... 

The NiY zeolite was also shown to be active for the cyclotrimerization of propyne with 1,2,4-trimethylbenzene being the main product. The activities of the above-mentioned transition metal ions for acetylene trimerization are not so surprising since simple salts and complexes of these metals have been known for some time to catalyze this reaction (161, 162). However, the tetramer, cyclooctatetraene, is the principal product in homogeneous catalysis, particularly when simple salts such as nickel formate and acetate are used as catalysts (161). The predominance of the trimer product, benzene, for the zeolite Y catalysts might be indicative of a stereoselective effect on product distribution, possibly due to the spatial restrictions imposed on the reaction transition-state complex inside the zeolite cages. 

In the 1950s two very effective pesticides were launched and their names were Dieldrin and Aldrin. As you may guess they were made by the Diels-Alder reaction. Aldrin is derived from two consecutive Diels-Alder reactions. In the first, cyclopentadiene reacts with acetylene to give a simple symmetrical cage molecule norbomadiene ... 

Manini, P Amrein, W. Gramlich, V. Diederich, F. Expanded cubane synthesis of a cage compound with a C56 core by acetylenic scaffolding and gas-phase transformations into fullerenes, Angew. Chem. Int. Ed. 2002,4339-4343. 

Early work regarding the polymerization of acetylene in zeolites was performed by Tsai et al. They reported that the extent of pol5nnerization on X-zeolites was related to the size of the alkali metal cations present in the cages, and that the cations activate the acetylene molecules. The photopolymerization of diacetylenes (3,5-octadiyne-l,8-diol) on various surfaces, including molecular sieves 5A and 13X, was examined. On polar surfaces, the first molecular layers are absorbed through hydrogen bonds, but due to their relative orientation these molecules do not polymerize. However, additional layers can be photopolymerized to form stable polymer films on the surface. 

The construction of C—B bonds in carboranes is effected by reaction of aikynes with polyboron hydrides. High-T and electric discharge-induced reactions between these reagents yield close cage systems, whereas milder conditions can lead to nido-carboranes. The preferred route to the parent closo-l,6-C2B4Hg and -2,4-C2B5H7 compounds involves the direct thermal reaction (500-600°C) of pentaborane(9) and acetylene in a continuous-flow system. Also formed is the smallest known closo-carborane, 1,5-0263115, in which the combined yields of products approach 70% and the product distribution of 0265117 0264115 0263115 is ca. 5 5 1 ... 

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