Polycyano compounds

The most important members of the cyanocarbon class are the alkenes tetracyanoethylene, hexacyanobutadiene, and tetracyanoquino dime than the alkanes tetracyanomethane and hexacyanoethane dicyano acetylene hexacyanobenzene tetracyanoquinone cyanocarbon acids oxacyanocarbons thiacyanocarbons and azacyanocarbons. Tetracyanoethylene is described first because its chemical versatility makes it a rich source of other polycyano compounds. Moreover, an understanding of its chemistry is helpful in understanding the chemistry of other cyanocarbons. 

For a review of complexes formed by tetracyanoethylene and other polycyano compounds, see Melby, L.R. in Rappoport The Chemistry of the Cyano Group, Wiley NY, 1970, p. 639. See also, Fatiadi, A.J. Synthesis, 1987, 959. 

Most organic acceptors used in the preparation of organic conducting materials belong to a class of polycyano compounds. The reasons are quite obvious if the unique properties of the cyano group are taken into account. It is a very strong acceptor and has a very small size with minimal steric strain. (Note the rod-shaped form of C N group.)... 

Polycyano Compounds in Chemistry of the Cyano Group (Z. Rappoport, ed.), pp. 423-638. Wiley (Interscience), New York, 1970. 70UP1 D. S. Donald, unpublished results (1970). 

Synthesis and Thermochemistry of Tricyanomethyl and Other Polycyano Compounds... 

A series of tricyanomethyl compounds were prepared in refluxing acetonitrile hy alkylating potassium tricyanometha-nide with alkyl iodides, allyl, propargyl, and benzyl bromides. Yields of 20-57% were obtained for mono- and difunctional halides with a reflux time of 72 hours. The heats of combustion of these tricyanomethyl compounds as well as of two polycyano compounds were measured using a Dickenson-type calorimeter, and heats of formation were calculated with a precision of approximately 1.0%. From Pitzers values for C—C and C—H bond energies, that of the tricyanomethyl moiety is calculated to be about 810 kcal./mole, and the tricyanomethyl group is less stable than expected from comparison with AH°f of propylcyanide. 

The isomeric 1,3,2,4-dithiadiazolium cation (40) is prepared by the (4 + 2)7t cycloaddition of the NS2+ cation to the C N triple bond of organic nitriles (see Figure 2). The NS2+ cation also reacts with polycyano compounds, for example, dicyano- and tricyanobenzenes, to give the corresponding bisand tris(dithiadiazolium) cations. 

In their review on cyanocarbon and polycyano compounds Ciganek et al. [11 a] wrote in 1970 Although their [i.e., the cyanoacetylenes] physical properties have received considerable attention, reports on the chemistry of these compounds are not as abundant as might be expected in view of their high reactivity . For nearly a quarter of a century this situation has not changed very much in fact, it was one of the reasons why we began our own work in this area. 

Cyanocarbon chemistry therefore covers a wide field of materials the properties of which depend largely on the presence of one ( nitriles ) or more ( polycyano compounds ) nitrile groups. The possible role of HCN and polycyano compounds in prebiotic synthesis is one of the most fascinating chapters in the processes that preceded the appearance of life on earth. ... 

The aim of this chapter is to present some recent and significant advances in the chemistry of polycyano compounds, especially from the last ten years. Only some patents will be mentioned. Dyes and other special compounds will not be discussed in detail. Literature on the subject that is already covered in reviews which have appeared since 1982 will only be referred to in connection with new results. A list of general reviews, which have been published on cyano compounds between 1981 and 1987, and short abstracts of their contents are given below as well as at the beginning of the sections dealing with malononitrile and with tetracyanoethylene ... 

Nitriles, Nitrilium Salts, C. Grundmann, 1985. This book section covers papers on preparations and reactions of mono- and dinitriles and polycyano compounds published from 1951 to approximately 1984 and contains 1518 references. 

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