The crystal structure of the title compound, C(6)H(8)N(+).C(8)HN(4)O(2)(-), is characterized by three independent ion pairs (A, B and C) in the asymmetric unit. Each ion pair consists of an anion and a cation, and the three ion pairs have similar geometric parameters. All the anions are arranged as dianion dimers via two N-H.O hydrogen bonds and the dimers form one-dimensional columns parallel to the b axis as a result of pi-pi interactions. The cations are also stacked, in two different ways: one type of stacking consists of alternating A and B cations, while the other type consists of C cations only. Each dianion dimer stack is surrounded by eight stacks of cations and is not connected directly to other dianion stacks.

In the title compound, C 8 H 12 N + ÁC 8 HN 4 O 2 À , the anion and cation lie on a crystallographic mirror plane and form planar ribbons via NÐHÁ Á ÁO [NÁ Á ÁO = 2.933 (4) A Ê , HÁ Á ÁO = 2.01 A Ê and NÐHÁ Á ÁO = 170 ] and NÐHÁ Á ÁN [NÁ Á ÁN = 3.016 (5) A Ê , HÁ Á ÁN = 2.15 A Ê and NÐHÁ Á ÁN = 169 ] hydrogen bonds. The ribbons are further linked via weak CÐHÁ Á ÁO and CÐHÁ Á ÁN hydrogen bonds. In adjacent planes, anions lie opposite cations; %±% interactions (separation a/2 = 3.520 A Ê ) exist between the anions and the cations, and stacks are formed, running along the a axis. The cations are disordered over two interpenetrating sites, with occupancies of 0.833 (5) and 0.167 (5). CommentWe have recently reported the synthesis and structure of the potassium salt of the title anion (Tafeenko et al., 2003). On the basis of the structural data and the calculated charge distribution on the atoms of the anion, the following types of anion± cation interaction can be postulated: (a)`isotropic' interactions, with each outer heteroatom of the anion taking part in the formation of a polyhedron enclosing the cation (Li, K, Na and Cs); (b) %±% stacking interactions, involving planar cations (e.g. pyridinium); (c) a transition metal±anion %system interaction (e.g. ferrocene); and (d ) interaction of the heteroatoms of the anion and the transition metal to form a coordination compound or chelate complex. An example of type a was described by Tafeenko et al. (2003). Interactions of type b were expected in the title compound, (I). Interactions of types c and d are the subject of further investigations.The synthesis of (I) was carried out as shown in the scheme above. The most remarkable features of this reaction are the main roles that are played by the two elementary particles (proton and electron) supplied by hydrogen iodide. The H atom interacts with the lone pair of the N atom of the N,Ndimethyl-N-phenylamine molecule to form a cation (see scheme), whereas the electron induces the rearrangement of the three-membered ring of 2,2,3,3-tetracyanocyclopropanecarboxylic acid to give an anion.In (I) (Fig. 1), all the atoms of the anion and the cation lie on a crystallographic mirror plane, with the exception of the methyl groups of the cation, which are located between planes and have an essential impact on the speci®c packing geometry. The bond lengths and angles in the anion are similar to those in the corresponding potassium salt (Tafeenko et al., 2003). The unique cation is disordered over two interpenetrating sites, with occupancies of 0.833 (5) and 0.167 (5) (see Experimental). The methyl groups enlarge the distances (half of the a axis) between the molecular planes and also prevent the formation of a more symmetrical anion±cation stacking. The shortest distance between an anion and a cation that form a stack and lie in adjacent mirror planes is 2.45 A Ê [H16BÁ Á ÁN4( 1 2 À x, 1 À y, z À 1 2 ); Fig. 2(a) and Table 1; atom H16B belongs to the C16 methyl group]. Although %±% interactions exist between anions and cations, these ...

The crystal structure of the title potassium salt, K(+).C(8)HN(4)O(2)(-), of the organic anion 3-cyano-4-(dicyanomethylene)-5-oxo-4,5-dihydro-1H-pyrrol-2-olate shows that the dicyanomethylene moiety is able to accept an electron in the same way as does tetracyanoethylene, to yield the novel product. The organic anion is nearly planar, with deviations caused by steric crowding among the exocyclic cyano groups. The K(+) cations lie within tricapped trigonal prisms that stack to form channels. The three-dimensional structure is completed by the formation of hydrogen-bonded chains by the anions.

A novel fast, convenient and inexpensive synthesis of 1',3'-dioxo-1',3'-dihydrospiro[cyclopropane-1,2'-indene]-2,2,3,3-tetracarbonitrile and dimethyl 2,3-dicyano-1',3'-dioxo-1',3'-dihydrospiro[cyclopropane-1,2'-indene]-2,3-dicarboxylate is reported. These compounds undergo double carbanion cleavage under the action of alcohols resulting in the formation of stable salts, containing new allylic-type anions with potential application in organic electronics and as ionic liquid components.