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Bromine tetrafluoride ion (CAS 23707-28-0) belongs to the family of hypervalent and interhalogen species that lie outside the valence rules of ordinary organic structure representations, so its polarity is worked out here by VSEPR electron counting rather than by a molecular-orbital calculation. As set out in the BrF4 Lewis Structure Guide, the species is built around a bromine centre bearing 4 ligands.
The electron count is straightforward. The neutral atoms supply 35 valence electrons, and the -1 charge adds 1 more, giving 36 in total. Each of the 4 ligand atoms completes an octet, consuming 32 electrons, which leaves 4 electrons — 2 lone pairs — on the central atom. With 4 bonding domains that gives a steric number of 6 and an electron-domain geometry of octahedral.
The molecular shape that follows is square planar; for five or more electron domains the modern picture is delocalised 3-centre 4-electron bonding rather than an sp3d orbital set, so no hybridization label is given. All 4 ligands are fluorine, so the bond dipoles are equal in magnitude and point in directions that sum to zero: the molecule has no net dipole.
Species of this class are reactive by construction: a halogen centre in a high formal oxidation state, carrying 4 ligands, is a strong fluorinating/oxidising centre and is handled accordingly. That reactivity — not the polarity — is what governs materials of construction, drying and packaging.
Polarity still matters for the practical question of how the substance behaves in a condensed phase. A square planar arrangement with equivalent ligands leaves no net dipole, which affects boiling point, solubility in polar media and the tendency to form ordered solids.
Because this is an ionic and/or highly reactive species, no dilute-gas relative permittivity is quoted: the Debye equation assumes neutral, freely rotating molecules in the gas phase, which does not describe this substance. No measured liquid dielectric constant is asserted either, because none was retrieved from the public record used here.
No partition coefficient is reported. Crippen/logP fragment methods are parametrised on neutral organic molecules and are not meaningful for a charged, hypervalent inorganic species, so quoting a logP would give a number with no physical content.
No GHS classification is asserted here. For a substance in this class the classification follows from the oxidising and corrosive properties of the specific ion, and must be taken from the supplier’s safety data sheet and from the ECHA record for CAS 23707-28-0.
Specify Bromine tetrafluoride ion by counter-ion, assay basis, moisture and hydrolysis limits, packaging and transport class, and confirm the classification from the safety data sheet rather than assuming it from the family.
The compounds below are the nearest structural relatives in the same catalogue. Dipole moments are calculated values from the same protocol (GFN2-xTB//MMFF94, gas phase, single conformer) where a structure could be computed; for the hypervalent entries no dipole number is quoted and the geometry column carries the VSEPR assignment instead.
| Compound | Dipole Moment | Approx. Gas εr | log P / XlogP | Water Solubility Behavior | Industrial Sourcing |
|---|---|---|---|---|---|
| BrF4 | 0 D | — | not meaningful | Reactive; hydrolyses | Guidechem supply listing |
| ClO2 | ≈3.59 D | — | logP ≈ -2.38 | Dissolves by dissociation; ionic hydration dominates | See supply listing |
| NF3 | ≈0.13 D | ≈1.0007 | logP ≈ 0.94 | Moderate (inferred from logP) | See supply listing |
| OF2 | ≈0.28 D | ≈1.0006 | logP ≈ 0.77 | Moderate (inferred from logP) | See supply listing |
| NCl3 | ≈0.48 D | ≈1.0030 | logP ≈ 1.75 | Moderate (inferred from logP) | See supply listing |
What this table makes clear is that the hypervalent entries cannot be ranked on the same numeric axis as the ordinary molecular compounds. Their behaviour is set by charge state and by ligand-field symmetry, so the VSEPR assignment is the useful comparison, not a dipole figure.
“For BrF 4 the honest answer is structural rather than numerical: 4 bonding domains and 2 lone pairs give a square planar shape, and symmetry cancels the bond dipoles. That is enough to decide how it will behave in a polar medium, and it is more useful than a dipole number obtained from a method that was never parametrised for this class.”
Regulatory status is substance- and jurisdiction-specific. For CAS 23707-28-0 the authoritative public sources are the ECHA registered-substance database for the EU and the OSHA and NIOSH tables for occupational exposure in the United States.
No GHS hazard statements for this substance are quoted here, because none were retrieved from the public record used to build this article. For hypervalent halogen species the operative hazards are oxidising power, corrosivity and the products of hydrolysis, and those must be taken from the supplier’s safety data sheet.
No occupational exposure limit is quoted. Publishing a limit that is not on the record would be worse than publishing none: obtain the applicable value from the OSHA Z-table, the NIOSH pocket guide or the equivalent national instrument.
From a compliance standpoint, the polarity question is secondary for this class. What matters is the oxidising and corrosive character of the ion, the fate of the halide on hydrolysis, and the abatement of any hydrogen halide generated on contact with moisture.
A purchase enquiry for Bromine tetrafluoride ion (CAS 23707-28-0) should specify the counter-ion, assay basis, moisture and hydrolysis limits, packaging and the transport classification required for a corrosive oxidising material, together with the regulatory status for the destination market.
Confirm the Guidechem supply listing for current availability, and require the certificate of analysis with the enquiry: for reactive inorganic ions, the identity of the counter-ion and the hydrolysis state usually decide whether a lot is usable.
Looking for commercial bulk supplies or technical documentation for Bromine tetrafluoride ion (CAS 23707-28-0)?
Nonpolar. The square planar shape with equivalent ligands cancels the bond dipoles exactly.
Square planar, from a steric number of 6 (4 bonding domains + 2 lone pairs).
The quantum-chemical protocol used elsewhere in this series was not parametrised for hypervalent halogen species, so a computed dipole would not be trustworthy. The polarity is therefore established from symmetry, which is exact wherever it applies.
No. Snyder P′ is defined for conventional liquid chromatographic solvents; a reactive inorganic ion is outside the scope of that scale.
Species of this class react with water rather than simply dissolving in it, producing the corresponding hydrogen halide and oxo-species. Treat contact with moisture as a chemical reaction to be controlled, not as a solubility question.
Counter-ion, assay basis, moisture and hydrolysis limits, packaging, and the transport classification for a corrosive oxidising material.
From the supplier’s safety data sheet and from the ECHA record for CAS 23707-28-0. No classification is asserted in this article because none was retrieved from the public record used here.
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