Boron Halides (B_bX_x)

Synthesis of BF₃ Na₂B₄O₇ + 6CaF₂ + 8H₂SO₄

2NaHSO₄ + 6CaSO₄ + 7H₂O + 4BF₃ Essentially B₄O₇^2- + "HF"

"BF₃" + "H₂O" Compare: NaCl + H₂SO₄

NaHSO₄+ HCl Synthesis of BCl₃ B₂O₃ + 3Cl₂ + 3C

2BCl₃ + 3CO (dry conditions) Synthesis of BI₃ NaBH₄ + 2I₂

BI₃ + NaI + 2H₂ Properties of B(Hal)₃ Compounds All planar, monomeric, strong Lewis acids (many complexes) Order of Lewis acid strength BF₃ < BCl₃ < BBr₃ < BI₃ Against electronegativity trend (F should induce strongest d⁺ charge on boron atom) Ans: p-bonding

Compare with Al: Al₂Cl₆ => weak intramolecular p-bonding dimer BCl₃ => strong intramolecular p-bonding monomer Reaction with Water BX₃ + 3H₂O

H₃BO₃ + 3HX X = Cl, Br, I whereas

H₃O⁺[BF₃(OH)]^-

BF₃(g) Due to very strong B-F bond Lower Halides B₂X₄, B₄X₄, B₈X₈, B₉X₉ all have B-B bonds

Figure 9: The lower boron halides-B₄Cl₄ has a perfect tetrahedral structure, the larger Bn units have long and short B-B distances

Boron Halides (BbXx)

Boron Halides (B_bX_x)