Tetracyano Ethylene

Tetraene 141 has been converted into various complex polycondensed adducts by reacting with a variety of dienophiles such as maleic anhydride, N-phenylmaleimide, N-phenyltriazolinedione,p-benzoquinone and tetracyano-ethylene carried out under thermal conditions. All cycloadditions occurred facial-diastereoselectively from an outside attack and provided monocycloadducts which had an exceptionally close relationship between diene and dieno-phile and then underwent intramolecular cycloaddition [125]. The reaction between 141 and p-benzoquinone is illustrated in Scheme 2.53. 

Several other complexes, M(CNBu )jL (L = an activated olefin), have also been reported recently (110). This group of complexes, with the ligands (L) including maleic anhydride, fumaronitrile, and tetracyano-ethylene, arises from isocyanide ligand substitution by the olefin. Less active olefins such as ethylene and diphenylacetylene, and azobenzene did not react. 

Crystal structure determinations have been carried out for the tetracyano-ethylene (139), azobenzene (52) and diphenylacetylene (52a) complexes, with molecular structures (XXXII) and (XXXIII). These complexes may... 

While 2-arylsubstituted methylenecyclopropanes reacted with tetracyano-ethylene (131, TCNE) to give [3 + 2] adducts, i.e. methylenecyclopentanes [37], via cleavage of the cyclopropyl CC bond, benzylidenecyclopropanes 156 and 157 behaved as dienes toward TCNE (Scheme 23). 

Tetracyano ethylene oxide, however, which represents a potential 1,3-dipole of the carbonyl ylide type, reacts with diphenyl cyclopropenone to give a cycloadduct of probable structure 415/417263, which may arise from insertion into the cyclopropenone C1(2)/C3 bond. 

In order to characterize electron acceptor (basic type) properties of the samples, tetracyano ethylene compound, known to be easily ionizable in TCNE radical anion, was introduced at room temperature in the samples outgassed at different temperatures up to 800°C. No ESR signal was observed. As steric hindrance could preclude the experiment, smaller molecules as SO and p-dinitro benzene were also introduced. Then too, no ESR spectrum could be detected although the ESR technique is extraordinarly sensitive. It may thus be concluded that the ZSM-5 and ZSM-11 materials did not exhibit electron donor (basic) properties as detectable by ESR. 

The crystal and molecular structure79 of a carbazole/tetracyano ethylene 1 2 complex reveals the presence of a hydrogen bond between the amino group of the carbazole and a nitrile nitrogen of tetracyano ethylene in the solid state, which resembles the stronger hydrogen bond observed between amines and the cyano group. 

Redox shuttles based on aromatic species were also tested. Halpert et al. reported the use of tetracyano-ethylene and tetramethylphenylenediamine as shuttle additives to prevent overcharge in TiS2-based lithium cells and stated that the concept of these built-in overcharge prevention mechanisms was feasible. Richardson and Ross investigated a series of substituted aromatic or heterocyclic compounds as redox shuttle additives (Table 11) for polymer electrolytes that operated on a Li2Mn40g cathode at elevated temperatures (85 The redox potentials of these... 

Nemykin et al. (2007) found a similar direct reaction between ferrocene (FcH) and tetracyano-ethylene (TCNE). The formation of a spectroscopically detected [FcH]+ [TCNE] was established. Cyanoferrocene and tricyanovinylferrocene as major and minor products were obtained, respectively. Although tricyanovinylferrocene was not the sole product of this reaction and its yield was approximately 30%, the direct method of its preparation was an important step toward materials for optically limiting devices. Untill now, the highly toxic chloromercurioferrocene was used for the preparation of tricyanovinylferrocene (Nemykin and Kobayashi 2001). 

Propose a reasonable mechanism that would account for the effect of tetracyano-ethylene. Does your mechanism suggest that tetracyanoethylene would be a particularly effective alkene for this purpose Explain. 

Scheme 6 represents coordinate polymers. A low-molecular-weight compound with multidentate groups on both ends of the molecule grows into a linear polymer with metal ions, and the polymer chain is composed of coordinate bonds. The parquetlike polymer complexes, poly(metal-phthalocyanine) and poly(metal-tetracyano-ethylene), are classified into Scheme 7. They are formed by inserting metal ions into planar-network polymers or by causing a low-molecular-weight ligand derivative to react with a metal salt and a condensation reagent.

Use an orbital interaction diagram to explain the observation that tetracyano-ethylene is very easily reduced to its radical anion. 

In another aspect of the mechanism, the effects of electron-donating and electron-with-drawing substituents (p. 843) indicate that the diene is behaving as a nucleophile and the dienophile as an electrophile. However, this can be reversed. Perchlorocyclopentadiene reacts better with cyclopentene than with maleic anhydride and not at all with tetracyano-ethylene, though the latter is normally the most reactive dienophile known. It is apparent, then, that this diene is the electrophile in its Diels-Alder reactions.893 Reactions of this type are said to proceed with inverse electron demand.m... 

The charge transfer complexes of linear polymers of polystyrene, poly(acenaphthalene) and poly(vi-nyl naphthalene) with tetracyano-ethylene and other electron acceptors have been studied (99). 

T etramethylammonium 1,1,2,3,3-pentacyanopropenide has been prepared by the base-catalyzed hydrolysis of tetracyano-ethylene,3 and by the present method, which is more economical of tetracyanoethylene. 

The method in Figure 17 often gives a product which contains traces of the corresponding (E,E)-diene. This isomer can be selectively removed from the (E., Z)-isomer, as described above, by formation of its Diels-Alder adduct with excess tetracyano-ethylene in tetrahydrofuran followed by chromatography on silica gel (cf. 17,18). Alternatively, the (E.,E)-isomer can be removed in many cases by the selective formation of its crystalline urea inclusion complex in methanol (cf. 13). 

Amines can act as reductants for excited states of other electron acceptors, too. Again, two possibilities exist (1) amine and acceptor form a CT (2) the complex formation takes place either with the excited state of the amine or with that of the electron acceptor (see discussions of ketone-amine combinations). Examples for the former principle are such combinations as DMA-nitrobenzene [105], triphenylamine-tetracyano ethylene, 4-nitrophenole, 4-aminochlorobenzene [106], tributylamine-tetrachloromethane [107], DMA-substituted chloroacetic adds [108, 109],... 

Further characterization of the ozone—mesitylphenylethylene complex produced at —150 °C was done by NMR and visible spectral studies. The low temperature NMR spectra of the starting olefin, the red complex (ozonized olefin at —150°C) and the dilute reaction mixture at —135°C containing the epoxide of 1-mesityl-1-phenylethylene are described in Table III. The —150 °C solutions of the olefin and the complex contain the same bands, the only difference being that the peaks were shifted slightly upfield in the formation of the complex. Such is typical of tt complexes with very little charge transfer, such as iodine and tetracyano-ethylene complexes of various aromatic molecules (5, 6). When the temperature of the ozonized reaction mixture was allowed to rise above about —145 °C, the NMR spectrum changed, giving rise to the characteristic peaks of the epoxide of 1-mesityl-l-phenylethylene. 

The reactions of 1-vinyl- (R = H) and Tprop-2-enyl- (R = Me) substituted tetrahydroindoles 690 with tetracyano-ethylene in equimolar amounts in DMSO afforded 3-tricyanovinyl-substituted derivatives 691 as the only products (Equation 166) <2001ARK37>. Hence, the iV-alkenyl substituent in the pyrroles does not react with tetracyanoethy-lene according to the [2-1-2] cycloaddition mechanism typical of other 1-vinyl-substituted heterocyclic compounds. 

Meier observed that the photoconductivity of )me dyes whidi are already known as efficient carrier generators can be enhanced by doping with electron acceptors (Table 2). He attenpted to apply this effect to the PVK/dye/acceptor system using Methylene Blue and pinacyanol as carrier generators and tetracyano-ethylene as an electron acceptor. Although no substantial increase in photocurrent was observed the spectral responce of the PVK/dye system was broadened to other wavelengths ... 

Rh(I), the complexes derived therefrom by displacement of C2H4 with the other ligands may involve a distorted octahedron about Rh(III) with two coordination sites occupied by the carbon atoms of C2F4 (463). A similar Rh(III) structure has been suggested (23) for the tetracyano-ethylene complexes [C2(CN)4]RhX(CO)[P(CeH5)3]2, (X = Cl, Br, or NCS), obtained by reaction of the olefin at room temperature with RhX(CO)[P(CeH5)3]2. 

Scheme 39. Cation radical probes quantitatively rule out an et mechanism for the addition of tetracyano-ethylene to electron rich alkenes.

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