Theoretical studies on Lewis acidity scale and bonding character of boron trihalides BX₃(X=F, Cl, Br, I) by DV-X_α quantum chemical approach

The Lewis acidity scale of boron trihalides BX₃ (X=F, Cl, Br, I) and character of the boron-halogen bonds have been studied by means of DV-X_α approach. Present results show that the acid strength of boron trihalides increases in the order BF₃333, in excellent agreement with experiments. Based on boron-halogen bonding character, the valence of boron atom in boron compounds can be considered as equal to five instead of three which seems to be more reasonable.