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339:. Pseudorotation is similar in concept to the movement of a conformational diastereomer, though no full revolutions are completed. In the process of pseudorotation, two equatorial ligands (both of which have a shorter bond length than the third) "shift" toward the molecule's axis, while the axial ligands simultaneously "shift" toward the equator, creating a constant cyclical movement. Pseudorotation is particularly notable in simple molecules such as
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The VSEPR theory also predicts that substitution of a ligand at a central atom by a lone pair of valence electrons leaves the general form of the electron arrangement unchanged with the lone pair now occupying one position. For molecules with five pairs of valence electrons including both bonding
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of molecular geometry, an axial position is more crowded because an axial atom has three neighboring equatorial atoms (on the same central atom) at a 90° bond angle, whereas an equatorial atom has only two neighboring axial atoms at a 90° bond angle. For molecules with five identical ligands, the
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and also with pi-electron withdrawing ability, as in the sequence Cl < F < CN. Both factors decrease electron density in the bonding region near the central atom so that crowding in the axial position is less important.
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pairs and lone pairs, the electron pairs are still arranged in a trigonal bipyramid but one or more equatorial positions is not attached to a ligand atom so that the molecular geometry (for the nuclei only) is different.
263:) with a central sulfur atom surrounded by four fluorine atoms occupying two axial and two equatorial positions, as well as one equatorial lone pair, corresponding to an AX
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with terminal iodine atoms in the two axial positions only and the three equatorial positions occupied by lone pairs of electrons (AX
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axial bond lengths tend to be longer because the ligand atom cannot approach the central atom as closely. As examples, in PF
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molecule with fluorine atoms in two axial and one equatorial position, as well as two equatorial lone pairs. Finally, the
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The five atoms bonded to the central atom are not all equivalent, and two different types of position are defined. For
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as an example, the phosphorus atom shares a plane with three chlorine atoms at 120° angles to each other in
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Isomers with a trigonal bipyramidal geometry are able to interconvert through a process known as
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the chlorines occupy two of the equatorial positions, indicating that fluorine has a greater
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or tendency to occupy an axial position. In general ligand apicophilicity increases with
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Molecular structure with atoms at the center and vertices of a triangular bipyramid
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443:, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "
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positions, and two more chlorine atoms above and below the plane (
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with one atom at the center and 5 more atoms at the corners of a
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the axial and equatorial are 214 and 202 pm respectively.
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179:= equatorial ligand (in plane perpendicular to unique axis)
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319:); another example of this geometry is provided by
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473:Interactive molecular examples for point groups
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468:Indiana University Molecular Structure Center
215:and the equatorial is 152 pm, and in PCl
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414:(2nd ed.). Prentice Hall. p. 407.
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161:Axial (or apical) and equatorial positions
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410:Housecroft, C. E.; Sharpe, A. G. (2004).
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33:Trigonal bipyramidal molecular geometry
211:the axial P−F bond length is 158
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169:Trigonal bipyramidal molecular shape
440:Compendium of Chemical Terminology
243:Related geometries with lone pairs
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382:"Trigonal bipyramidal molecules"
483:Animated Trigonal Planar Visual
174:= axial ligand (on unique axis)
1:
728:Tricapped trigonal prismatic
733:Capped square antiprismatic
712:Bicapped trigonal prismatic
273:T-shaped molecular geometry
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686:Capped trigonal prismatic
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253:seesaw molecular geometry
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453:10.1351/goldbook.AT06990
341:phosphorus pentafluoride
185:phosphorus pentachloride
148:phosphorus pentachloride
137:phosphorus pentafluoride
676:Pentagonal bipyramidal
222:In the mixed halide PF
180:
721:Coordination number 9
695:Coordination number 8
669:Coordination number 7
643:Coordination number 6
617:Coordination number 5
591:Coordination number 4
565:Coordination number 3
544:Coordination number 2
168:
702:Square antiprismatic
660:Pentagonal pyramidal
624:Trigonal bipyramidal
337:Berry pseudorotation
331:Berry pseudorotation
277:chlorine trifluoride
257:sulfur tetrafluoride
157:) in the gas phase.
133:pentagonal bipyramid
129:triangular bipyramid
18:Trigonal bipyramidal
535:Coordination number
412:Inorganic Chemistry
87:Coordination number
777:Molecular geometry
655:Trigonal prismatic
577:Trigonal pyramidal
519:Molecular geometry
478:Molecular Modeling
386:Creative Chemistry
362:Molecular geometry
267:E molecule in the
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125:molecular geometry
121:trigonal bipyramid
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681:Capped octahedral
634:Pentagonal planar
421:978-0-13-039913-7
236:electronegativity
202:According to the
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16:(Redirected from
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707:Dodecahedral
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389:. Retrieved
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275:is found in
269:AXE notation
255:is found in
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204:VSEPR theory
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199:positions).
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105:μ (Polarity)
598:Tetrahedral
72:Point group
766:Categories
650:Octahedral
391:2023-02-07
368:References
357:AXE method
189:equatorial
293:triiodide
117:chemistry
99:90°, 120°
751:Category
582:T-shaped
351:See also
283:), an AX
47:Examples
146:), and
603:Seesaw
551:Linear
418:
309:linear
197:apical
61:Fe(CO)
435:IUPAC
323:, XeF
295:ion (
193:axial
556:Bent
416:ISBN
279:(ClF
271:. A
251:The
119:, a
449:doi
447:".
347:).
343:(PF
259:(SF
195:or
152:PCl
115:In
768::
437:,
400:^
384:.
327:.
226:Cl
213:pm
177:eq
172:ax
141:PF
79:3h
58:,
52:PF
511:e
504:t
497:v
451::
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345:5
325:2
317:3
315:E
313:2
302:3
297:I
289:2
287:E
285:3
281:3
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261:4
228:2
224:3
217:5
209:5
154:5
150:(
143:5
139:(
109:0
91:5
77:D
63:5
54:5
20:)
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