Pentagonal bipyramid coordination

Figure 31.6 The polymeric strucmre of AnFs (An = Pa, U, Np) and Pads, showing the distorted pentagonal bipyramidal coordination of the metal.

Figure 31.7 (a) The octahedral anion in Cs2[U02CU]. (b) Pentagonal bipyramidal coordination of U in dinuclear [U02(02CMe)2L]2 (L = OPPhs, OAsPhs). (c) Hexagonal bipyramidal coordination of U in uranyl nitrate, U02(N03)2-6H20. 

Most of the EF-hand motifs have one water (—X). On the other hand, in Rhizopus chinensis aspartic proteinase (Suguna et al., 1987) there is one main-chain carbonyl oxygen bound to calcium and six water molecules to complete the pentagonal bipyramidal coordination. Calcium coordination has been measured in several viruses, such as Southern bean mosaic virus (Silva and Rossmann, 1985), satellite tobacco necrosis virus (Jones and Liljas, 1984), and tomato bushy stunt virus IV (Olson et al., 1983). 

The basic structure of the hydrated oxalato complex, NaNpC CyiVSPkO, is made up of infinite chains of composition [Np02C2O4(H2O)]" connected by Na+ ions and H20 molecules in a three-dimensional network. The neptunium atom is at the centre of a pentagonal bipyramid, coordinated to four O atoms from two C204 groups and a fifth from the water molecule in the equatorial plane.17915... 

Five crystal modifications of anhydrous U02(MeC02)2 have been reported. The structure of the dihydrate consists of chains of pentagonal bipyramidal coordination polyhedra in which half of the MeC02 groups link adjacent bipyramids and the remainder are chelated to individual uranium atoms one water molecule is bonded to each uranium atom.2783... 

In the polymeric acetamide complex of the chromate, [U02Cr04(MeC0NH2)2]B> the structure consists of chains of (U02)0S pentagonal bipyramidal coordination polyhedra in which the equatorial plane is made up from three oxygen atoms from [Cr04]2- tetrahedra and two from the acetamide molecules.300 Similarly, in the dimeric DMA complex with the acetate, [U02(MeC02)2(DMA)]2, the structure consists of two pentagonal bipyramidal polyhedra... 

Figure 12-6 Structure of Fe(DTPA)2- found in the salt Na2[Fe(DTPA)] - 2H20. The seven-coordinate pentagonal bipyramidal coordination environment of the iron atom features three N and two O ligands in the equatorial plane (dashed lines) and two axial O ligands. The axial Fe-O bond lengths are 11 to 19 pm shorter than those of the more crowded equatorial Fe-O bonds. One carboxyl group of the ligand is uncoordinated. [D. C. Flnnen, A. A. Pinkerton, W. R. Dunham, R. H. Sands, and M. O. Funk. Jr..

Cyclic pentamines adopt folded coordination modes in octahedral coordination, with configurational isomerism possible if different chelate segments are present.26 Pentagonal bipyramidal coordination with planar macrocycles has been observed for tetradentate pyo macrocycles, e.g. (18) and (30).21 Reported hexaaza macrocycles fold to give octahedral coordination arrangements, again with the possibility of configurational isomerism.27... 

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