Pentagonal bipyramidal geometry

The structure of [Re(Et2)dtC3(CO)] consists of monomeric Re with a distorted, pentagonal, bipyramidal geometry, having an axial CO group. This is the first, clear-cut example of monomeric 7-coordinate rhe-nium(III), as other examples usually involve Re-Re bonds 216). 

C09-0133. Among the halogens, only one known molecule has the formula X 7. It has pentagonal bipyramidal geometry, with five Y atoms in a pentagon around the central atom X. The other two Y atoms are in axial positions. Draw a ball-and-stick model of this compound. Based on electron-electron repulsion and atomic size, determine the identities of atoms X and Y. Explain your reasoning. (Astatine is not involved. This element is radioactive and highly unstable.)... 

Figure 9.24 The pentagonal bipyramidal geometry of some AX molecules.

Figure 9.27 The AX5E2 pentagonal bipyramidal geometry of the XeF5 ion.

A dithiocarbamate complex Bi(S2CNEt2)I2(bipy), prepared from [Bi(S2CNEt2)I2] with a fivefold excess of bipy (142), exists as an iodide bridged dimer reminiscent of 41. The central bismuth atom is seven-coordinate with a pseudo-pentagonal-bipyramidal geometry occupied by a terminal I atom and a bipy nitrogen atom [Bi-N 2.56(1) A] in... 

Pentagonal bipyramidal geometry, for metal coordination numbers, 7 574 Pentaheteroglycans, classification by structure, 4 723t Pentalene ligand, 24 772-773 Pentamethine dyes, 9 505 Pentamethylantimony, 3 77 Pentamethylcyclopentadiene, 25 116 Pentamethylcyclopentasiloxane,... 

It is clear from the data in Table II that protein Ca -binding sites do not have perfectly octahedral or pentagonal bipyramidal geometry (see also Color Plate 1). Figure 4 provides some clues as to which ligand types deviate most from ideal geometry, and the nature of the deviations. First, it can be seen that the observed deviations of ligands from their ideal positions are not due entirely to coordinate errors. The majority of the... 

A monohydrate60 of K4V(CN)7] and the preparation of the anhydrous material have also been reported.178 The geometry of the anions in all cases has been suggested to be the same.179 The IR spectrum of the dihydrate shows two bands (2100 and 2070 cm-1) similar to those in solution (2104 and 2027 cm-1). Therefore the anion in solution must be [V(CN)7]4- with a pentagonal bipyramidal geometry. Attempted studies179,180 of the ESR spectrum have been unsuccessful due to the disproportionation products [VO(CN)5]3- and [V(CN)6]4-. 

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