The synthesis and crystal and molecular structure are described of (C 2 B 10 H 11 )C 6 H 4 (C 2 B 10 H 10 )C 6 H 4 (C 2 B 10 H 11 ) (4), an acyclic assembly of three ortho-carborane units connected through their carbon atoms by two para-phenylene units. For this compound, and published structures of other arylortho-carboranes, correlations are noted between the orientations of aryl substituents and cage carbon-carbon distances (C1-C2). Ab initio RHF/6-31G * and MP2/6-31G * studies on 1-phenylortho-carborane, PhC 2 B 10 H 11 , and other model systems have been used to explore the variations in their energies, C1-C2 bond lengths, and C2-C1-C aryl bond angles with the orientation of their aryl groups, variations believed to reflect weak interactions between the aryl substituents' π systems and the carborane cages. The synthesis of a pentafluorophenyl derivative of 4,

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Reaction of allyltribromogermane (2), readily available from dibromo(1,4-dioxane)germanium(II) (1) and allylbromide, with tris(2-tributylstannoxyethyl)-amine (4) gives 1-allylgermatrane (3) in almost quantitative yield. 3 crystallizes from n-pentane as a colourless crystalline solid which was characterized by 1H and 13C NMR spectroscopy and by an X-ray crystal structure study. The “atrane” skeleton shows a strong conformational disorder; the Ge-N distance of 2.208(3) Å suggests the presence of a coordinative Ge-N bond. Treatment of 1-allylgermatrane (3) with CH2N2 in the presence of catalytic amounts of Pd(OAc)2 affords 1-cyclopropylmethylgermatrane (5) in high yield

C-44931 level, and the MEP calculation, corresponding to the location of each non-bonded atomic contact, at the 6-311 **leveL The MEP was stored incrementally on a grid with its origin at the centroid of the solvent molecule. Computer programs were then used to analyze geometrical preferences and the correlation of the MEP with the directionality of the intermolecular interactions. The impact of crystal packing and specific intem1o!ecular interactions on molecular structure has been illustrated by the example of five anthraquinone de1ivatives. Compounds 1 and 2 show analogous behaviour in solutions: in non-polar solvents the fom1 A is a predominant one, whereas polar solvents displace the equilib1ium towards ketoenannne fonn B. HO *ru;moThe crystal structure of 1 is built up from centrosymmetlic dimers (interplanar distance 3.43 A), where two molecules are Hbonded in addition. As a result only form B takes place in crystaL No signs of H-bonding or other specific interactions are observed in the crystal stll.JCture of 2, hence the crystal smTounding displaces here the equilibrium towards fonn A like low-polar solvent.Visible spectra of anthraquinone dyes are also related to the motif of crystal packing. The crystal structures of 1,4-bis(mesitylamino)anthraquinone(3),1,4-bis(phenylamino )anthraquinone ( 4) and 1-hydroxy-4-(p-tolylanlino)anthraquinone (5) are built up from separated molecules, dimers and stacks with interplanar distance 3.35 and 3.50 A respectively. As a result the maximum in reflection spectmm of 3 is blue shifted by 1000 em-I relative to the absorption spectll.lm in solutions, whereas 4 shows red shift by 700 em-I accompanied by the direct manifestation of vibrational stll.lcture. Am·active intramolecular edge-to-face type interactions between aromatic moieties have been identified by X-Ray studies and NMR in a range of simple nitrones, oxaziridines and in,1ines. IJ;n=ol~ular hydrogen t? nnd-aromatic 1ing distances of 2.60A, 2.66A, 2.70A, 2.73A and 2.78A are observed. The Hw1ter-Sanders mles (C.A. HW1ter and J.K. Sanders, J. Am. Clzem. Soc., 1990, 112, 5525) are applied to the interactions and are found to be in agreement with the observations. Analysis of the crystal lattices have shown sinlllar intennolecular interactions affecting the c1ystal packing, in some cases quite sigrlificantly. One case showed evidence in the NMR for an intramolecular edge-to-face type interaction winch was not observed in the solid state where several intermolecular aromatic-aromatic interactions seemed to be controlling the geomeuy. The cr polmization of the atoms in the 1ings is proposed as being of importance in determining the type of interaction observed and hence the geometry. PS11.07.15 ATTRACTIVE EDGE-TO-FACEPS11.07.16 ORIENTATIONAL DISORDER OF SOME ORGANIC MOLECULAR CRYSTALS STUDIED BY ATOM-ATOM POTENTIALS.