Title: electron-deficient molecule
Long Title: IUPAC Gold Book - electron-deficient molecule
DOI: 10.1351/goldbook.08804
Status: current

Definition
Molecule that has fewer valence electrons than required for forming normal two-center two-electron chemical bonds and thus contains multicenter chemical bonds.

Notes
1) Binding of atoms into molecules, clusters and macroscopic bodies in electron-deficient compounds is mediated by delocalized electrons, each being shared by three or more atoms.
2) Metals are typical electron-deficient compounds in which extreme delocalization of electrons across the whole macroscopic body exists.
3) Boron, boranes, carboranes and related compounds are typical compounds with electron-deficient molecules in which boron and some other atoms are bound by multicenter two-electron bonds, such as by the two-electron three-center bond in which two electrons bind three atoms.

Related Terms
- delocalized electrons: https://goldbook.iupac.org//terms/view/08789
- electron-rich molecule: https://goldbook.iupac.org//terms/view/08805
- extent of electron delocalization: https://goldbook.iupac.org//terms/view/08818

Source
- PAC, 2022, 94, 15. 'Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)' on page 28 (https://doi.org/10.1515/pac-2020-0501)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/08804/html
- json: https://goldbook.iupac.org/terms/view/08804/json
- xml: https://goldbook.iupac.org/terms/view/08804/xml

Citation: Citation: 'electron-deficient molecule' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.08804
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Accessed: 2026-04-18T08:32:38+00:00