Related Experiment Video
Updated: Jun 12, 2026
13:56
Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
Published on: October 12, 2019
Recoupled pair bonding in PF(n) (n = 1-5).
1Department of Chemistry, University of Illinois at Urbana-Champaign, Box 92-6, CLSL, 600 S. Mathews, Urbana, Illinois 61801, USA. dewoon@illinois.edu
The Journal of Physical Chemistry. A
|June 17, 2010
Summary
This study explores hypervalency in phosphorus fluoride (PF(n)) species, revealing a new bonding mechanism called recoupled pair bonding. This mechanism allows for the formation of novel PF(n) structures previously not observed.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Inorganic Chemistry
Background:
- Previous studies investigated hypervalency in SF(n) and ClF(n) species.
- Hypervalent bonding involves energetically favorable uncoupling of electron pairs to form new bonds, termed recoupled pair bonding.
- Unlike sulfur and chlorine, ground state phosphorus (P((4)S)) lacks 3p(2) pairs for recoupling, but its 3s(2) pair is susceptible.
Purpose of the Study:
- To characterize the structures and energetics of phosphorus fluoride (PF(n)) species (n=1-5).
- To investigate the occurrence and implications of recoupled pair bonding in PF(n) formation.
- To explore bonding in both ground and excited states of phosphorus.
Main Methods:
- Utilized coupled cluster calculations with the RCCSD(T) method.
- Employed triple- and quadruple-zeta quality correlation consistent basis sets.
- Analyzed the energetics and structures of various PF(n) isomers and transition states.
Main Results:
- Identified PF(3)(a(3)B(1)) formed via recoupled pair bonding, lying significantly above the normal covalent PF(3)(X(1)A(1)) but still bound.
- Characterized two isomers of PF(4): one with two covalent and two hypervalent bonds, and another with three covalent and one hypervalent bond.
- Located the transition state between the two PF(4) isomers.
- Described low-lying excited state species formed from P((2)D) using recoupled pair bonding.
Conclusions:
- Recoupled pair bonding is a significant factor in the formation of hypervalent PF(n) species.
- The 3s(2) electron pair in phosphorus is crucial for enabling recoupled pair bonding when other pathways are exhausted.
- This study expands the understanding of bonding in hypervalent compounds and opens avenues for exploring novel chemical structures.
Related Concept Videos
01:27¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
01:17Spin–Spin Coupling: One-Bond Coupling
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
02:24Polar Covalent Bonds
Covalent bonds are formed between two atoms when both have similar tendencies to attract electrons to themselves (i.e., when both atoms have identical or fairly similar ionization energies and electron affinities). Nonmetal atoms frequently form covalent bonds with other nonmetal atoms. For example, the hydrogen molecule, H2, contains a covalent bond between its two hydrogen atoms. When two separate hydrogen atoms with a particular potential energy approach each other, their valence orbitals...
02:45Valence Bond Theory
Overview of Valence Bond Theory