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metal-organic compounds
The title compound, [Pd(C19H17NO4)I(C18H15P)], crystallizes with four independent molecules in the asymmetric unit. The main difference between the molecules is the disposition of the PPh3 ligand, for which in each molecule one ring is perpendicular to the ligand plane, but may be directed in either direction away from the plane; of the four molecules, two represent each possible direction. The independent molecules are arranged to form a chain parallel to [101] with an approximate translation of (a+c)/4 between successive molecules, excluding the PPh3 rings. This leads to a systematic weakness of the reflections with h + l ≠ 4n.
organic compounds
In 2′,5′-dimethyl-p-terphenyl, C20H18, which displays pseudosymmetry (the true space group is Pna21, but less satisfactory refinement can also be achieved in Pbcn), the molecules are linked into chains by two short C—H
π interactions to the centroid of the central ring. In 2′,5′-bis(bromomethyl)-p-terphenyl, C20H16Br2, the polar CH2Br groups cause molecules to aggregate via C—HBr and BrBr interactions, forming a layer structure, in which the phenyl rings project outwards from the central, more polar, region.
π interactions to the centroid of the central ring. In 2′,5′-bis(bromomethyl)-p-terphenyl, C20H16Br2, the polar CH2Br groups cause molecules to aggregate via C—HBr and BrBr interactions, forming a layer structure, in which the phenyl rings project outwards from the central, more polar, region.organic compounds
The monosubstituted derivative 4-ethynyl[2.2]paracyclophane, C18H16, (I), and the four disubstituted isomers, 4,12-, (II), 4,13-, (III), 4,15-, (IV), and 4,16-diethynyl[2.2]paracyclophane, (V), all C20H16, show the usual distortions of the [2.2]paracyclophane framework. The crystal packing is analyzed in terms of C—Hπ interactions, some with Hπ as short as 2.47 Å, in which the cyclophane rings and/or the triple-bond systems may act as acceptors. For compounds (I) and (IV), the known `7,11'-type cyclophane packing is observed, with a herring-bone pattern of molecules in a layer structure.
π interactions, some with Hπ as short as 2.47 Å, in which the cyclophane rings and/or the triple-bond systems may act as acceptors. For compounds (I) and (IV), the known `7,11'-type cyclophane packing is observed, with a herring-bone pattern of molecules in a layer structure.organic compounds
In the title compound, C18H16, the [2.2]paracyclophane geometry is restrained to a considerable extent despite the introduction of the extra C=C bridge; typical paracyclophane features, such as the elongated C-C bridges, are still observed. However, the bridgehead atoms of the C=C bridge are forced into unusually close proximity [2.657 (3) Å], which in turn causes the rings to be rotated to an interplanar angle of 13.7 (2)°. The packing involves hexagonally close-packed layers of molecules parallel to the xy plane, corresponding to the known `7,11' pattern of paracyclophanes, but without significant short intermolecular contacts.
organic compounds
![[triple bond]](/logos/entities/z-tbnd_rmgif.gif)
C hydrogen bonds in the structures of two poly(cyano)-substituted ring systemsIn benzene-1,2,3-tricarbonitrile, C9H3N3, the packing of the two independent molecules is three-dimensional and complex, involving inter alia bifurcated (C—H)2N systems from neighbouring CH groups. In [2.2]paracyclophane-4,5,12,13-tetracarbonitrile, C20H12N4, the [2.2]paracyclophane systems display the usual distortions, namely lengthened C—C bonds and widened sp3 angles in the bridges, narrow angles in the six-membered rings at the bridgehead atoms, and flattened boat conformations of the rings. The molecules are linked by a series of C—HN interactions to form layers parallel to the ab plane.
N systems from neighbouring CH groups. In [2.2]paracyclophane-4,5,12,13-tetracarbonitrile, C20H12N4, the [2.2]paracyclophane systems display the usual distortions, namely lengthened C—C bonds and widened sp3 angles in the bridges, narrow angles in the six-membered rings at the bridgehead atoms, and flattened boat conformations of the rings. The molecules are linked by a series of C—HN interactions to form layers parallel to the ab plane.
