diborane Lewis Structure

diborane Lewis Structure: B₂H₆ Lewis Structure, trigonal planar Geometry, sp2 Hybridization & Polarity

diborane Key Facts

The diborane Lewis structure is 3 B–H single bond; the central B has 3 electron domains (0 lone pairs), giving a trigonal planar electron-domain arrangement and a trigonal planar molecular geometry with a 120° bond angle. B is best described as sp2-hybridized, and diborane is nonpolar because the bond dipoles cancel by molecular symmetry.

Figure 1: Lewis Structure of diborane (B₂H₆)

Chemical Formula	B₂H₆
CAS Number	19287-45-7
Total Valence Electrons	12
Lewis Structure	3 B–H single bond
Electron-Domain Geometry	trigonal planar
Molecular Geometry	trigonal planar
Hybridization Model	sp2 (central B)
Bond Angle	120°
Polarity	Nonpolar molecule

PubChem (CID 12544637) and NIST list diborane as B ₂H ₆ with CAS 19287-45-7; molecular weight ≈ 27.67 g/mol. View CAS 19287-45-7 dictionary details on Guidechem →

Applications of diborane (CAS 19287-45-7)

As a hydride of B, diborane is typically a strong reducing agent, a potential fuel component, or a precursor in inorganic and organometallic synthesis. Many pnictogen/sulfur hydrides are toxic, foul-smelling and pyrophoric or flammable, and are handled with appropriate ventilation and inert-atmosphere technique.

Reducing Agent Electron-rich hydrides reduce metal centers and functional groups in synthesis.

Precursor / Feedstock Source of B in the preparation of derivatives and doped materials.

Handling Often toxic/flammable/pyrophoric; inert atmosphere and active ventilation required.

Procurement Note "diborane" is supplied in multiple commercial grades and package sizes. Specify purity, grade, moisture/impurity limits, package (cylinder, drum or bulk) and intended process, and use CAS 19287-45-7 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the diborane Lewis structure we first count the total valence electrons. B₂H₆ contains 2×3 (B) + 6×1 (H); the net charge of 0 gives a total of 12 valence electrons to place.

The central atom is B. It is the least electronegative atom capable of forming multiple bonds and is surrounded by the more electronegative terminal atom(s); hydrogen, when present, always occupies a terminal position. Electronegativity considerations place the electron density toward the terminal atom(s).

Valence-electron count

Total valence electrons = 2×3 (B) + 6×1 (H) = 12 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place B at the center and connect each surrounding atom with a single bond, complete octets on the terminal atoms, and place any remaining electrons on the central atom. The resulting electron distribution is: 3 B–H single bond; no lone pairs on B.

Counting bonding and nonbonding electrons around B therefore satisfies the octet/expanded-octet requirement for the drawn structure.

B–H ×3

B: 0 lone pairs, 3 bonding domains

3 bonding domains + 0 lone pairs = 3 electron domains

Octet Rule: Why B Has Eight Electrons B forms 3 bond(s) and retains 0 nonbonding electron(s), reaching an octet. No expanded octet is required for this second-row (or octet-satisfying) central atom.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 3 electron domains around B arrange to minimize mutual repulsion, giving an trigonal planar electron-domain geometry.

Because 0 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is trigonal planar; the B bond angle is set to 120° rather than the ideal value for the electron-domain geometry.

Repulsion hierarchy

A useful VSEPR approximation is: lone pair–lone pair repulsion > lone pair–bonding pair repulsion > bonding pair–bonding pair repulsion. With 0 lone pair(s) on B, the lone-pair domains occupy positions that minimize overall repulsion while pushing the bonding domains (and therefore the bonded atoms) closer together.

Hybridization & Formal Charge

In the conventional localized-bond model, B uses sp2 hybrid orbitals to form the 3 equivalent electron-domain directions (3 bonding + 0 lone pair).

Formal-charge check

Formal charge on central B = V − N − ½B = 3 − 0 − ½×6 = 3. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp2 is a compact model for the 3 electron-domain directions around B; full quantum-chemical treatments use molecular orbitals.

Is diborane Polar or Nonpolar?

diborane is nonpolar. Although individual B–terminal bonds are polar when the atoms differ in electronegativity, the trigonal planar geometry makes their vector sum zero, so there is no net molecular dipole.

Expert Quote — Structural Chemistry Perspective

A common misconception is that polar bonds guarantee a polar molecule. diborane shows the opposite: identical bond dipoles arranged with trigonal planar symmetry cancel exactly, yielding a nonpolar species.

Interpretation consistent with standard VSEPR / molecular-geometry references.

Its nonpolar character governs solvation and intermolecular behavior; specify grade and handling when sourcing.

Structural Comparison Table

Species	Formula	Central Atom	Electron Domains	Molecular Geometry	Polarity
diborane	B₂H₆	B	3	trigonal planar	Nonpolar
Boron trifluoride	BF₃	B	3	trigonal planar	Nonpolar
Boron trichloride	BCl₃	B	3	trigonal planar	Nonpolar
Diborane	B₂H₆	B	3	trigonal planar	Polar

Practice question Starting from the 12 valence electrons of B₂H₆, draw the Lewis structure and confirm the central B atom is sp2-hybridized with trigonal planar geometry. What happens to the bond angle if one terminal atom is replaced by a more electronegative substituent?

Looking for industrial bulk or specified-grade supplies of diborane (CAS 19287-45-7)? Browse Supplier on Guidechem →

FAQs

Is B₂H₆ polar or nonpolar?

diborane is nonpolar. Its trigonal planar symmetry cancels the bond dipoles exactly.

What is the Lewis structure of diborane?

3 B–H single bond; no lone pairs on B. It uses all 12 valence electrons and the preferred structure carries a formal charge of 3 on the central atom.

What is the bond angle in diborane?

The B angle is about 120°. Lone-pair repulsion compresses the angle from the ideal trigonal planar value.

What is the hybridization of B in diborane?

The conventional model is sp2. diborane has 3 electron domains around the central B.

What is the CAS number of diborane?

The CAS number is 19287-45-7. PubChem (CID 12544637) and NIST identify this with B₂H₆; use it to locate suppliers and database records.

References

PubChem CID 12544637, diborane. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, diborane. Formula, CAS Registry Number and thermochemical / spectroscopic data.
IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for diborane (CAS 19287-45-7).

Technical scope: Lewis structures, VSEPR and hybridization are model-based descriptions for chemical communication and structure prediction; actual molecular electronic structure is more accurately represented by molecular-orbital and quantum-chemical methods. Commercial grades vary substantially by supplier and intended use; CAS 19287-45-7 identifies the substance, not a universal purity specification.

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diborane Lewis Structure

diborane Lewis Structure