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[4′-(Dimethylamino)biphenyl-4-yl]dimesitylborane (BNB) and 4-[4′-(Dimethylamino)pnenylazo]phenyldimesityl-borane (BNA) have been investigated by X-ray diffraction; crystallographic data were used to calculate dipole moments in the ground state and the hyperpolarizability coefficient βo was measured by the EFISH technique for each derivative. The results show that the trivalent boron group is an efficient electron acceptor compared to other known acceptors such as the nitro group. Organoboron derivatives are promising candidates for nonlinear optical materials.

[Fe(C 9 H 19 )(C 5 H 5 )](C 12 H 4 N 4 ) 2 cristallise dans P2 1 /m avec a = 7,914, b = 30,983 et c = 6,629 A, β = 102,38 °, Z = 2; affinement jusqu'a R = 0,042. La structure consiste en couches de TCNQ separees par le ferrocene. Les effets steriques des groupes methyl ne se manifestent pas seulement sur le metallocene, mais egalement sur l'empilement du TCNQ.

The crystal structure of the title compound, tris[3,4,3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalene] tetrabromocuprate(2−), (C 10 H 8 S 8 ) 3 [CuBr 4 ], is classified as the α phase and contains two independent BEDT-TTF [BEDT-TTF = 3,4,3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalene] molecules (A and B) stacked as ABBABB along the c axis. The dihedral angle between the A and B molecules is 5.3 (1)° and between the stacks is 67.1 (2)°. The shortest intermolecular distances observed between molecules in adjacent columns are S...S 3.485 (2) and S...C 3.428 (4) A, and between anions and cations Br...S 3.777 (1) A

The structure of the title compound, tris[3,4,3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalene] dibromodichlorocuprate(2 − ), (C 10 H 8 S 8 ) 3 [CuBr 2 Cl 2 ], consists of alternate layers of BEDT-TTF molecules [BEDT-TTF = 3,4,3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalene] and pseudo-square-planar [CuBr 2 Cl 2 ] 2− anions. Two crystallographically independent BEDT-TTF molecules (A and B) are observed with approximate charges of 0 and +1, respectively. The BEDT-TTF molecules are stacked in an ABBABB fashion with a dihedral angle of 67° between the stacks, as in the α phase; short S...S contacts result in two-dimensional conducting layers

Cristallisation dans Pī avec a=7,8665, b=7,8575, c=13,4458 A, α=95,67, β=101,36, γ=111,08°, z=2; affinement jusqu'a R=0,0489. Les cations organiques DMCTTF + s'empilent le long de l'axe a, selon un mode de type zigzag. Ils forment des colonnes conductrices de dimeres faiblement lies. Les anions AsF 6 - sont localises dans les cavites, laissees par les molecules organiques. Les atomes As sont situes sur le centre d'inversion de leur octaedre

s Service): alors que bis(trim6thyl6ne)-3,4;3',4' tr Spencer, Cava & Garito, 1976) et l'influence de la perte de symr la temperature de transition est 81 K. Un signal RPE de grande largeur laisse pr6voir des interactions tridimensionnelles fortes, plus fortes que celles pr6sentes dans les cristaux de T T F T C N Q et H M T T F T C N Q (hexam&hyl+net6trathiafulval6ne-t&racyanoquinodim6thane). 2812 TRIMETHYLENETETRATHIAFULVALENE-TETRACYANOQUINODIMETHANE Partie exp6rimentale

Description de l'evolution de l'empilement cristallin sous contrainte. La temperature et la pression conduisent a une diminution des distances intra- et interstrates dans le rapport 1:1,5. Description de la mise en ordre de l'anion PF 6

C14H1684.CI2H4N4, triclinic, PL a = 13.730(4), b = 6.832(2), c = 7.081 (2) A, a = 105.00(5), ~? = 78.48(5), y = 74.87(5) °, V = 593.3 A 3, Z = 1, F(000) = 268, M, = 516, d c = 1.445 Mg m -3, g(Cu Ka) = 3.72 mm-k The structure was solved by the heavy-atom method and refined to an R of 0.056 for the 1856 independent diffractometer- observed reflexions. OMTTF and TCNQ are alter- nately stacked along the (001) direction; the average perpendicular separation between the molecular planes is 3.53A. Bond lengths in TCNQ show that the constituent molecules in this compound are essentially neutral. The electrical conductivity of this compound, measured on single crystals, is cl ___ 10 -5 f~-I cm-l. Davidson & Simpson (1965). Ceux des atomes de soufre ont 6t6 corrig6s pour la dispersion anomale. La structure a 6t6 r6solue par la m6thode de l'atome lourd, l'analyse de la fonction de Patterson ayant permis de placer les atomes de soufre. L'affinement de la structure a 6t6 conduit de la faqon suivante: affinement avec agitation thermique isotrope (R = 0,14) puis anisotrope (R = 0,07) des positions des atomes S, N, O, C (les atomes de carbone des groupes m6thyl6nes pr6sentent un d6sordre de position; seuls les Tableau 1. Coordonn~es atomiques et facteurs d'agitation thermique Introduction. Le complexe OMTTF-TCNQ a 6t6 form6 par r6action d'oxydo-r6duction entre l'oxydant TCNQ, synth6tis6 selon la mh seule la m6thode de diffusion 6vaporation a permis de cristalliser ce complexe. S(l) S(2)