Hexagonal bipyramidal molecules

The structure of the 2,6-dihydroxybenzoate, [U02 (HO)2C6H3C02 2(H2O)2]-8H2O consists of an irregular hexagonal bipyramidal arrangement with two bidentate carboxylate groups and two H20 molecules in trans positions in the equatorial plane.2780... 

The crystal structure of antimony pentachloride, SbCls, is hexagonal (D (, P63 jmmc, a0 = 7.49, and c0 = 8.01 A) with two molecules in the cell. The molecules are hep giving the simple notation 2P(h). In Figure 4.26, we see that the trigonal bipyramidal molecules have their C3 axes parallel to c0, the packing direction. The axial Sb—Cl distance is 2.34 A and that in the equatorial plane is 2.29 A. The closest Cl—Cl distances (3.33 A) are between axial Cl atoms between adjacent molecules. 

Fig. 7. The structure of K2[(U02)2(C204 ]-4H20. Hexagonal bipyramids bridge through bidentate oxalate linkages to form anionic sheets. Charges balancing K cations as well as interlayer H2O molecules have been omitted for clarity.

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