electron-deficient compound

Electron-deficient compounds are species where an atom does not achieve a full octet of valence electrons. This is less common than hypervalent compounds but still occurs. A prime example is boron trifluoride (BF₃). In BF₃, the boron atom only shares six valence electrons, not the typical eight required for a full octet.1

While Lewis structures can be drawn to satisfy the octet rule, these are energetically less favorable than the incomplete-octet structure for BF₃. This electron deficiency is precisely why BF₃ is a useful catalyst, as the boron atom can form bonds with other atoms using the vacancies in its valence shell, facilitating chemical reactions. Electron-deficient compounds are rare because most atoms are large enough that electron pair delocalization is not the dominant structural feature.12