In Group 13, what is the significance of boron tri-halides related to Lewis acidity?

Boron tri-halides, such as BF3, BCl3, and BBr3, are well-known for their Lewis acidity. The Lewis acid behavior of these compounds is largely due to the electron-deficient boron atom. Boron has only six valence electrons in its outer shell when it forms three covalent bonds with halogens, resulting in an incomplete octet. This electron deficiency makes boron capable of accepting a pair of electrons from Lewis bases, which are electron-rich species.

When boron tri-halides accept electron pairs, they can form complexes, showcasing their Lewis acid character. This ability to coordinate with other molecules allows them to participate in a variety of chemical reactions, often serving as catalysts in organic synthesis and other applications. The behavior of boron tri-halides as Lewis acids is fundamental in understanding their reactivity and interactions with other chemical species in inorganic and organic chemistry.

The other options do not accurately represent boron tri-halides; they do exhibit significant Lewis acid behavior, are more than just weak acids, and indeed can form complexes, countering the claims of the incorrect answers.